Houdini 18.0 Nodes Geometry nodes

RBD Bullet Solver geometry node

Runs a dynamic Bullet simulation.

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The RBD Bullet Solver is a wrapper around a DOP network to simplify the running of Bullet simulations. Like most RBD SOPs, it is based on a three input SOP, with 2 additional inputs.

The first input is the render geometry. It will be used as simulation geometry if none is provided in the third input.

The second input is the constraint geometry, used to instantiate dynamic constraint relationships between simulated pieces. These can be created when fracturing the geometry using an RBD Material Fracture SOP or created explicitly using the RBD Constraints From Lines, RBD Constraints From Curves, or RBD Constraints From Rules amongst other methods. They need a name point attribute connecting them to their respective pieces and a constraint_name primitive attribute matching the constraint relationship DOP’s data name, and can have primitive attributes to define their behavior during the course of the simulation. You can also use the RBD Constraint Properties SOP to set these up.

The third input is the proxy geometry, a simplified representation of the render geometry, better suited for fast simulations. It will be used as the simulation geometry when provided.

The fourth input provides the collision geometry. Packed geometry is recognized and can be configured with the RBD Configure SOP to drive their behavior individually. Some pieces could be animated, some pieces set to deform, while others may be set to use spheres as geometry representation.

The fifth input provides the guiding geometry. This can either be packed geometry or a mesh that can be split into various parts by connectivity which will can be packed into discreet pieces. If the simulation geometry isn’t packed, it will be converted to packed fragments internally for simulation. The RBD Configure SOP can be used to pack and set attributes on the simulation geometry and collision geometry to drive the various bullet objects' behavior. For more information, see the Guided simulations help page.

Note

The guide geometry will use transformation matrices from its various pieces to drive the guided pieces. For packed objects, their intrinsic transforms are used. Unpacked geometry will be packed per name attribute (if available else per connectivity) on the capture start frame and transformed onwards. A single deforming mesh as guide geometry will therefore need to first be broken up into various clusters in order to satisfy the requirements for guiding to work as expected.

You can dive into the solver to add DOP nodes to apply special forces and other SOP Solvers. This feeds into the rigid body solver DOP’s pre-solve input and can be used to customize the behavior of the simulation and extend the node’s default capabilities.

If using collisionignore, the simulation geometry object can be referred to as rbd_object, the fourth input’s object can be referred to as collision_object, and the generated ground plane or heightfield as groundplane.

When adding impacts, the impact points are available via a named null OUT_IMPACT_POINTS that can be retrieved with an object merge.

Many visualizer options are available to get instant feedback on the simulation and the constraints to help tune constraint breaking thresholds. Additionally, a viewport inspector, accessible via a right-click context menu option in the viewport when the node state is active, allows you to inspect any particular primitive’s attributes by simply hovering over it. In order to get constraint information from the viewport inspector, set the RBD Bullet Solver SOP’s output for view flag to Constraint Geometry.

Name attribute types

It’s very important that the RBD Bullet Solver SOP receives consistent name attribute types. If you mix point and primitive name attributes, the solver is unlikely to be able to reconcile this mismatch and will either fail completely or give you erroneous results.

Always check the incoming geometry (by middle-clicking on the node) for a primitive name attribute. The only time you should see point name attributes is if you are dealing with Packed Fragments, in which case point name attributes are expected.

Be careful about having both point and primitive name attributes or any case where some geometry has name attributes and some do not. Unpacking with the Unpack SOP or the RBD Unpack SOP, will prefer point attribute names over prim attribute names. If you mix and match these attribute types, have inconsistencies in the name attributes for points and prims, or have some geo with no name attributes at all, you could lose all your prim names and end up with empty strings instead, or end up with an obscure dataset.

The RBD Bullet Solver SOP attempts to find empty names on either points or prims and will assume the name from their counterpart. However, it’s best to avoid this case.

Visualizers and viewport tools

The RBD Bullet Solver provides a number of visualizers to help tune and debug the RBD simulation. When the node state is active, various guide geometries can be displayed (bullet geometry representation, guide preview, etc), constraint information can be displayed as a histogram with information about the min and max values and a viewport inspector can be activated to help with reading attribute values for the primitive under the mouse pointer.

Viewport Inspector

The viewport inspector displays attribute values about the output primitive under the mouse pointer. To view information about the various outputs, switch the Bullet Solver node’s output for view flag to the desired output. For example, to view information about constraints, switch the Bullet Solver node’s output for view flag to "Constraint Geometry". You can use the "1", "2" or "3" hotkeys in the viewport to switch between "Geometry", "Constraint Geometry" or "Proxy Geometry" respectively, or press "4" to toggle between them.

To view attributes that are generated by the DOP network, you will need to first transfer those attributes to the geometry. In the "Advanced" tab’s "Output" section, select the attributes to transfer and enable them on either the Geometry or Proxy Geometry. You can specify which attributes to display information about on the Inspector’s Attributes parameter.

Parameters

Reset Simulation

Clears the entire simulation caches.

Start Frame

What frame on the Houdini playbar that the simulation should begin at.

Solver

Time Scale

Scales the effective time of the Bullet solve. This can be used to create bullet-time like effects where the physics of the Bullet solver run at a different rate than the Houdini playbar. A value of 2 will cause objects to fall twice as fast, and 0.1 will slow it to a tenth the speed.

Substeps

The number of substeps for each simulation step, used by Bullet internally. Increasing this number will increase the resolution of the simulation.

In Bullet’s documentation:

maxSubSteps = substeps + 1
fixedTimeStep = timeStep / substeps

Houdini adds 1 to maxSubSteps to account for roundoff errors during division when substeps > 1.

See Stepping the World.

Constraint Iterations

The more iterations you use, the more accurate the constraint and collision handling will be.

See Advanced constraint solver settings.

Bullet Object

Emits RBDs

When on, input simulation geometry and constraint geometry available at the current frame will be added to the simulation. A suffix "_" + int(frame * 100) will be appended to their names. For example, piece0-1 at frame 1 will be renamed piece0-1_100, while piece0-1 at frame 2.5 will be renamed piece0-1_250

Overwrite Attributes from SOP

When enabled, specifies a list of point attributes that will be updated on each frame from the simulation geometry. The name point attribute is used to find the matching point from the SOP geometry.

Bullet Data

Collision Padding

A padding distance between shapes, which is used by the Bullet engine to improve the reliability and performance of the collision detection. You may need to scale this value depending on the scale of your scene. This padding increases the size of the collision shape, so it is recommended to enable Shrink Collision Geometry to prevent the collision shape from growing.

This option is not available Plane geometry representations.

Linear Threshold

The sleeping threshold for the object’s linear velocity. If the object’s linear speed is below this threshold for a period of time, the object may be treated as non-moving.

Angular Threshold

The sleeping threshold for the object’s angular velocity. If the object’s angular speed is below this threshold for a period of time, the object may be treated as non-moving.

Physical

Density

The mass of an object is its volume times its density.

Rotational Stiffness

When an object receives a glancing blow, it will often acquire a spin. The amount of spin acquired depends on the shape and mass distribution of the object, known as the inertial tensor.

The Rotational Stiffness is a scale factor applied to this. A higher stiffness will make the object less liable to spinning, a lower value will make it more ready to spin.

Bounce

The elasticity of the object. If two objects of bounce 1.0 collide, they will rebound without losing energy. If two objects of bounce 0.0 collide, they will come to a standstill.

Friction

The coefficient of friction of the object. A value of 0 means the object is frictionless.

This governs how much the tangential velocity is affected by collisions and resting contacts.

Collisions

Use Collisions

Enables the collision object.

Bullet Data

Geometry Representation

The shape used by the Bullet engine to represent the object.

Convex Hull

Default shape for the object. The Bullet Solver will create a collision shape from the convex hull of the geometry points.

Concave

The Bullet Solver will convert the geometry to polygons and create a concave collision shape from the resulting triangles. This shape is useful when simulating concave objects such as a torus or a hollow tube. However, it is recommended to only use the concave representation when necessary, since the convex hull representation will typically provide better performance.

Box

Bounding box of the object.

Capsule

Bounding capsule of the object.

Cylinder

Bounding cylinder of the object.

Compound

Creates a complex shape consisting of Bullet primitives (including boxes, spheres, and cylinders). You will need to use the Bake ODE SOP.

Sphere

Bounding sphere of the object.

Plane

A static ground plane.

Initial Object Type

Specifies the initial state of the objects. The active, animated, and deforming point attributes can be used to vary these values on a per object basis. For animated and deforming objects, the name point attribute is used to find the matching point from the SOP Path.

Create Active Objects

The objects will be simulated and react to other objects in the simulation.

Create Static Objects

The objects will not move or react to other objects in the simulation.

Create Animated Static Objects

The objects' transforms will be updated on each timestep from the SOP Path, but the objects will not react to other objects in the simulation.

Create Deforming Static Objects

The objects' collision shapes will be rebuilt on each timestep from the SOP Path, but the objects will not react to other objects in the simulation.

Create Deforming Active Objects

The objects will be simulated and react to other objects in the simulation, and their collision shapes will also be rebuilt on each timestep from the SOP Path.

Collision Padding

A padding distance between shapes, which is used by the Bullet engine to improve the reliability and performance of the collision detection. You may need to scale this value depending on the scale of your scene. This padding increases the size of the collision shape, so it is recommended to enable Shrink Collision Geometry to prevent the collision shape from growing.

This option is not available Plane geometry representations.

Physical

Bounce

The elasticity of the object. If two objects of bounce 1.0 collide, they will rebound without losing energy. If two objects of bounce 0.0 collide, they will come to a standstill.

Friction

The coefficient of friction of the object. A value of 0 means the object is frictionless.

This governs how much the tangential velocity is affected by collisions and resting contacts.

Ground

Add Ground Plane

None

No ground plane will be added.

Ground Plane

Adds a ground plane to the simulation.

Height Field

Adds a heightfield static object to the simulation.

Height Field

SOP path to the height field geometry.

Use Deforming Geometry

Enable deforming heightfield geometry.

Initial State

Ground Position

Location of the center of the ground plane.

Rotation

Rotation of the ground plane.

Physical

Bounce

The elasticity of the object. If two objects of bounce 1.0 collide, they will rebound without losing energy. If two objects of bounce 0.0 collide, they will come to a standstill.

Friction

The coefficient of friction of the object. A value of 0 means the object is frictionless.

This governs how much the tangential velocity is affected by collisions and resting contacts.

Dynamic Friction Scale

An object sliding may have a lower friction coefficient than an object at rest. This is the scale factor that relates the two. It is not a friction coefficient, but a scale between zero and one.

A value of one means that dynamic friction is equal to static friction. A scale of zero means that as soon as static friction is overcome the object acts without friction.

Forces

Gravity

The amount of force to apply to a unit-massed object. Because the force is scaled by the mass, objects will undergo this acceleration.

If your units are meters, seconds, and kilograms, -9.81 is a good value for Earth’s gravity.

If your units are feet, seconds, and pounds, -32 is a good value for Earth’s gravity.

Add Drag

Enable the POP Drag DOP.

Drag

Wind Velocity

This is the speed which the particles will be dragged to.

If it is zero, they are dragged to a stop.

Otherwise, it defines a wind speed which the particles will accelerate to.

Add Drag Spin

Enable the POP Drag Spin DOP.

Drag Spin

Axis Relative to Particle’s Orientation

The provided goal axis will be rotated into the particle’s own reference frame. Thus a value of (0, 1, 0) will be up in the space of the particle rather than in world space.

Goal Axis

The desired axis for the particle to spin around in its rest state.

Goal Spin Speed

How fast, in degrees per second, that the particle should spin around the given axis when it has reached its rest state. If this is zero, it will drag the spin to a stop.

If it is positive, it will spin-up or down until it matches this.

Spin Resistance

How quickly the particle should match the goal spin speed.

Constraints

Constraints

Glue

See the Glue Constraint Relationship DOP.

Soft

See the Bullet Soft Constraint Relationship DOP.

Hard

See the Hard Constraint Relationship DOP.

ConeTwist

See the Cone Twist Constraint Relationship DOP.

Slider

See the Slider Constraint Relationship DOP.

Breaking Thresholds

Overwrite with SOP

This flag will re-import the network whenever it is set, allowing a completely animated constraint behavior.

Breaking

Constraint Names

Constraint names for which constraint breaking will be computed.

Note

Glue constraints are the only constraints that have implicit breaking so have not been added to the default constraint names.

Group

Constraint primitives to be evaluated for breaking.

Mode

Delete Constraints

Constraint geometry with attribute values above the specified threshold will be deleted.

Switch to Next Constraint

Constraint geometry with attribute values above the specified threshold will switch to their next_constraint_name if available or deleted.

At Frame

Break constraints at the specified frame.

From Frame

Breaking will only be evaluated from the specified frame onwards.

Angle Threshold

The angle (in radians) beyond which a constraint will break.

Var

Denotes a percentage increase/decrease from the user base input. For example, a threshold value with a value of 1000 and a variance set to 0.1 will result in values between 900 and 1100, while a variance of 1 will result in values ranging from 0 to 2000.

Scaling

Scales the threshold value by given attribute value.

Angle Attribute

The name of the attribute used to multiply the angle threshold with.

Update from Input

Updates the attribute value from the input constraint geometry. This allows for animating thresholds through geometry attributes for fine control.

Distance Threshold

The distance between anchor points beyond which a constraint will break.

Note

The restlength is subtracted from the constraint distance so as to avoid automatically breaking long constraints. In order to have a distance threshold relative to restlength, set the Distance Threshold to 1 + <factor>, enable scale by attribute, and set the Distance Attribute to restlength. For example, to automatically break constraints that stretch 10% of their length, set the distance threshold to 1.1

Force Threshold

The force beyond which a constraint will break.

Note

As of Houdini 18.0, glue constraints update the force attribute on the constraint geometry such as it represents the length of the delta between the 2 constrained pieces' forces, multiplied by their average mass. To break glue constraints based on force relative to their strength, set the force threshold to 1, enable scale by attribute, set Force Attribute to strength.

Impact Threshold

The impact beyond which a constraint will break.

Torque Threshold

The torque beyond which a constraint will break.

Plastic Flow Threshold

The linear plastic flow beyond which a constraint will break.

Note

Only available on soft constraints with linear plasticity enabled.

Angular Plastic Flow Threshold

The angular plastic flow beyond which a constraint will break.

Note

Only available on soft constraints with angular plasticity enabled.

Use VEXpression

Input VEX code to update or modify constraints. For example, to weaken a glue constraint’s strength based on applied force, @strength = max(0, @strength - f@force);

The bullet packed primitives are connected to the second input and the specified SOP geometry is connected to the third input.

VEXpression SOP Path

The path to the SOP geometry for use in the VEXpression snippet via its third input.

Evaluation Node Path

VEX functions like ch() usually evaluate with respect to this node. Enter a node path here to override where the path search starts from. This is useful for embedding in a digital asset, where you want searches to start from the asset root.

Impacts

Add Impact Data

Enables the Impact Analysis DOP.

Time Threshold

The minimum amount of time (in seconds) between recorded impact points. Higher values give fewer impact points and bigger gaps in time.

Impact Threshold

The minimum amount of impact force for recorded impact points. Higher values only create points for stronger impacts and ignore weaker impacts.

Distance Threshold

The minimum distance between recorded impact points. Higher values give fewer impact points and bigger gaps in space.

Guided Simulation

Use Guides

Enables simulation guiding.

Use Guided Neighbors

Enables using a minimum number of connected neighbors per guide cluster as a condition to break guiding. This helps to prevent isolated pieces from remaining guided when all their direct neighbors within that guide cluster have broken free.

Setup

Group

The simulation geometry packed primitives to be guided.

Start Frame

The reference start frame where guiding attributes will be captured to the simulation geometry.

End Frame

End frame of the guide animation.

Mode

Near Point

Guide names are based on proximity to guide pieces center of mass.

Near Surface

Guide names are based on nearest guide surface position.

Max Distance

Distance beyond which simulation geometry will not acquire a guide. When this value is -1 no maximum is used.

Strength

Guide strength.

Distance to Strength

Multiply the strength based on distance to guide geometry.

Blend

Add a blend attribute to the simulation pieces which will be multiplied by the global blend value.

Ensure Neighbor

When a guided piece has no neighbors within its guide cluster, it will inherit the nearest piece’s guide target.

Constraints

Remove Intra-Guide Constraints

Deletes constraints between pieces belonging to different guide clusters.

Note

constraints between guided and unguided pieces are unaffected.

Group

Constraint geometry primitives to consider when removing intra-guide constraints.

Simulation Settings

Method

Choose between a direct velocity (v) and angular velocity (w) update or a target velocity (targetv) and target angular velocity (targetw) update method to use when guiding.

Velocity

Updates v and w directly - this is the most precise way of guiding, however it can lead to jittering when collisions get in the way.

Target Velocity

Updates targetv and targetw attributes, used in combination with the Air Resistance and Drag parameters, to compute a force that will move the object towards the desired velocity and a torque that will move the object towards the desired angular velocity. This is more forgiving that the direct v and w updates and helps eliminate jittering as pieces are allowed to deviate further from their guided positions and orientations. The solver’s implicit drag option needs to be on for this to work properly.

Air Resistance

Specifies how important it is to match the target velocity (targetv) and target angular velocity (targetw).

Drag

When an object is dragged by the targetv and airresist attributes, this attribute is used to further scale the drag amount.

Blend

Blend amount to lerp guided velocity and angular velocity with natural velocity and angular velocity. Lowering this value results in a soft dampened spring-like constraint and can help reduce some jittering that may occur when guided velocities and angular velocities struggle with collisions.

Guide Release Thresholds

Instantaneous

Linear Threshold

When the distance between the computed guided position and the resulting post-solve position is greater than the linear threshold multiplied by guide strength, the piece will become unguided.

Angular Threshold

When the angle (in degrees) between the computed guided orientation and the resulting post-solve orientation is greater than the angular threshold multiplied by guide strength, the piece will become unguided.

Distance Threshold

When the difference between the distance of the guide piece to the bullet primitive and their distance at rest increases beyond the distance threshold multiplied by guide strength, the piece will become unguided.

Accumulated

Linear Threshold

When the accumulated distance between the computed guide position and the resulting post-solve position is greater than the distance threshold multiplied by guide strength, the piece will become unguided.

Angular Threshold

When the accumulated angle (in degrees) between the computed guide orientation and the resulting post-solve orientation is greater than the angular threshold multiplied by guide strength, the piece will become unguided.

Distance Threshold

When the accumulated difference between the distance of the guide piece to the bullet primitive and their distance at rest increases beyond the distance threshold multiplied by guide strength, the piece will become unguided.

Guided Neighbors

Minimum Neighbors

When the number of connected neighbors within the same guide cluster drops below this number, the piece will become unguided. Pieces with no guided neighbors at rest will be ignored.

Post-Guide VEXpression

Runs a VEX snippet after the guiding computation has occurred. This enables you to modify the computed velocity or target velocity for better control over the resulting guided behaviour.

Use VEXpression

Enable the post-guide wrangle.

VEXpression Group

Only affect a group of bullet packed primitives. By default, the "__guided" group is selected to only affect primitives currently being guided.

VEXpression

Input VEX code to update or modify guided bullet packed primitives.

The guide geometry is connected to the second input and the input simulation geometry is connected to the third input.

Evaluation Node Path

VEX functions like ch() usually evaluate with respect to this node. Enter a node path here to override where the path search starts from. This is useful for embedding in a digital asset, where you want searches to start from the asset root.

Advanced

Bullet World Scale

Scales the bullet world by this number and scales output geometry by the inverse of this number. This helps with issues that can arise with tiny pieces.

Simulation geometry attributes that are scale dependent are scaled accordingly (density, velocity, accelmax, speedmin, speedmax, bullet_collision_margin, bullet_shrink_amount).

Constraint geometry attributes that are scale dependent are scaled accordingly (restlength, strength, plasticthreshold). Forces and thresholds are scaled accordingly where applicable.

Warning

When scaling the bullet world, constraint VEXpressions are run in the scaled world, so geometry lookups will need to take that into consideration. Similarly, custom forces applied in the editable forces subnet will need to be aware of the scale.

DOP Network

Cache Memory (MB)

Specifies how much memory in megabytes can be consumed by the cache for this simulation. Once this limit is exceeded, old cache entries are deleted.

Substeps

The default timestep expression will use this parameter to control how many substeps the DOP simulation should perform every frame.

Bullet Solver

Sleeping Time

When an object’s speed has been below its linear and angular speed thresholds for this amount of time, the object is eligible to be deactivated and put to sleep. This can improve performance for simulations where there are some stationary objects.

Note

An object can only be put to sleep once any nearby objects and objects it is constrained to are also eligible to be put to sleep.

Contact Breaking Threshold

Distance threshold used by the Bullet engine when determining whether a cached contact point should be discarded. Adjusting this value according to the scene scale may also improve performance, as it influences the margin added to objects' bounding boxes.

Use Implicit Drag

Applies a more accurate damping for the drag described by the targetv and airresist point attributes, instead of applying it as an explicit force. This also affects how the targetw and spinresist attributes are applied for angular drag.

Constraint Solver

Constraint Solver

Specifies which constraint solver Bullet will use to resolve collisions and constraints. Both solvers parallelize the workload, but differ in the strategy they use to do so. Parallel Gauss-Seidel (Islands) will be faster in cases that involve many small "islands" of interacting objects (for example, a large number of small separate book stacks), whereas Parallel Gauss-Seidel (Graph Coloring) should perform better when such "islands" are few and large (such as a huge collapsing building).

Although results obtained with these solvers will generally not be identical, qualitative differences should be minor.

Randomize Constraint Order

Specifies that the constraints should be randomly reordered before each of the Constraint Iterations. This may improve stability, but incurs a minor performance hit.

Ensure Islands are Independent

Specifies that the solver should ensure that changes to an island of interacting objects (including adding, removing, or repositioning objects) do not cause other islands to produce different simulation results, unless those changes cause the objects to interact. Otherwise, the solver only guarantees that resimulating with the exact same input to the solver will produce the same results. Enabling this option may incur a minor performance hit, and may change the simulation results slightly.

Solve Tolerance

Allows the constraint solver to terminate before performing the full number of Constraint Iterations if it is close enough to the solution. Larger values can increase performance at the cost of accuracy.

Constraint Force Mixing

Increasing the CFM (constraint force mixing) parameter will make contact constraints softer, and may increase the stability of the simulation. Contact constraints may be violated by an amount proportional to this parameter times the force that is needed to enforce the constraint.

Error Reduction Parameter

Specifies what proportion of the constraint error for contact constraints will be fixed during the next simulation step. If ERP (error reduction parameter) is set to 0, constrained objects will drift apart as the simulation proceeds. If ERP is set to 1, the solver will attempt to fix all constraint error during the next simulation step (however, this may result in instability in some situations). A value between 0.1 and 0.8 is recommended for most simulations.

Split Impulse

Tries to make interpenetrating objects split without adding velocity (to keep objects from explosively flying apart).

See Split Impulse.

Penetration Threshold

Split Impulse only applies when objects interpenetrate by more than this distance. This number should be negative (representing less than 0 distance between the objects).

See Split Impulse.

Split Impulse ERP

Overrides the Error Reduction Parameter for contact constraints where the penetration distance is within the Penetration Threshold and Split Impulse is enabled.

Output

Transfer Attributes

Transfer attributes to output simulation points.

Transfer to Geometry

Transfers the attributes listed above to the output geometry.

Transfer to Proxy Geometry

Transfers the attributes listed above to the output proxy geometry.

Visualize

Display Visualization Geometry

Enables the display of the guide and visualization geometry.

Simulation Geometry

Show Geometry Representation

Displays the bullet geometry representation used by the solver.

Note

This can impact the performance of the simulation quite dramatically so is recommended to only use for debugging purposes at the start of the simulation.

Show Active (Green)

Displays active pieces as a green wireframe overlay.

Show Sleeping (Red)

Displays sleeping pieces as a red wireframe overlay.

Show Guided (Blue)

Displays guided pieces as a blue wireframe overlay.

Show Guide Capture

Displays the guided geometry transformed by the guide (no simulation). The hue represents the guide clusters, the value represents the strength attribute value. In this mode, the viewport inspector will display information about the guide.

Guide Capture Frame

Applies a timeshift to the guided capture geometry to visualize the guide influence at the given frame.

Guide Capture Blend

Displays the guided geometry transformed by the guide (no simulation). The hue represents the guide clusters, the value represents the blend attribute value.

Show Guide Neighbor Count

Displays the guide neighbor count as a ramp of colors from red to blue. Black represents no guide neighbors, white are pieces for which use guide neighbor count is disabled.

Constraints

Show Constraints

Enables the display of the constraint geometry.

False Color Mode

None

No color is applied to the constraint geometry.

Angle

A histogram is displayed in the upper left corner showing the range of angle values across the constraint geometry, with information about the minimum and maximum values. Constraint geometry is colored accordingly.

Angular Plastic Flow

A histogram is displayed in the upper left corner showing the range of angular plastic flow values across the constraint geometry, with information about the minimum and maximum values. Constraint geometry is colored accordingly.

Distance

A histogram is displayed in the upper left corner showing the range of distance values across the constraint geometry, with information about the minimum and maximum values. Constraint geometry is colored accordingly.

Force

A histogram is displayed in the upper left corner showing the range of force values across the constraint geometry, with information about the minimum and maximum values. Constraint geometry is colored accordingly.

Impact

A histogram is displayed in the upper left corner showing the range of impact values across the constraint geometry, with information about the minimum and maximum values. Constraint geometry is colored accordingly.

Plastic Flow

A histogram is displayed in the upper left corner showing the range of plastic flow values across the constraint geometry, with information about the minimum and maximum values. Constraint geometry is colored accordingly.

Torque

A histogram is displayed in the upper left corner showing the range of torque values across the constraint geometry, with information about the minimum and maximum values. Constraint geometry is colored accordingly.

Constraint Name

Information about the constraint names is displayed in the upper left corner showing the color assigned to each primitive with a given constraint_name attribute. Constraint geometry is colored accordingly.

Custom

A histogram is displayed in the upper left corner showing the range of user defined attribute values across the constraint geometry, with information about the minimum and maximum values. Constraint geometry is colored accordingly.

Attribute

Specify the float attribute name to display a histogram for and color the constraint geometry accordingly.

Additional Guides

Show Impacts

When impacts are enabled, displays the impact points as red spheres.

Show Ground

Display the ground geometry.

Show Collision

Display the collision geometry.

Show Collision Geometry Representation

Displays the collision geometry representation used by the solver.

Note

This can impact the performance of the simulation quite dramatically so is recommended to only use for debugging purposes at the start of the simulation.

Inspector

Attributes

Specify the list of attributes to display in the viewport through the inspector.

Examples

GuidedRBDBulletSolver Example for RBD Bullet Solver geometry node

This example demonstrates the use of the RBD Bullet Solver SOP guiding feature.

KatamariDamacy Example for RBD Bullet Solver geometry node

This example demonstrates the use of the RBD Bullet Solver SOP with custom forces and dynamic constraint generation.

MaterialFractureTutorial Example for RBD Bullet Solver geometry node

This example contains a setup that is used in the tutorial seen here: destruction/tutorials/intro_to_mbd_1

RBDBulletSolver Example for RBD Bullet Solver geometry node

This example contains a number of various uses for the RBD Buller Solver SOP.

RBDBulletSolverEmission Example for RBD Bullet Solver geometry node

This example demonstrates the use of the RBD Bullet Solver SOP emissions feature.

See also

Geometry nodes

  • Adaptive Prune

    Removes elements while trying to maintain the overall appearance.

  • Add

    Creates Points or Polygons, or adds points/polys to an input.

  • Agent

    Creates agent primitives.

  • Agent Clip

    Adds new clips to agent primitives.

  • Agent Clip Properties

    Defines how agents' animation clips should be played back.

  • Agent Clip Transition Graph

    Creates geometry describing possible transitions between animation clips.

  • Agent Collision Layer

    Creates a new agent layer that is suitable for collision detection.

  • Agent Configure Joints

    Creates point attributes that specify the rotation limits of an agent’s joints.

  • Agent Constraint Network

    Builds a constraint network to hold an agent’s limbs together.

  • Agent Definition Cache

    Writes agent definition files to disk.

  • Agent Edit

    Edits properties of agent primitives.

  • Agent Layer

    Adds a new layer to agent primitives.

  • Agent Look At

    Adjusts the head of an agent to look at a specific object or position.

  • Agent Prep

    Adds various common point attributes to agents for use by other crowd nodes.

  • Agent Proxy

    Provides simple proxy geometry for an agent.

  • Agent Relationship

    Creates parent-child relationships between agents.

  • Agent Terrain Adaptation

    Adapts agents' legs to conform to terrain and prevent the feet from sliding.

  • Agent Transform Group

    Adds new transform groups to agent primitives.

  • Agent Unpack

    Extracts geometry from agent primitives.

  • Agent Vellum Unpack

    Extracts geometry from agent primitives for a Vellum simulation.

  • Alembic

    Loads the geometry from an Alembic scene archive (.abc) file into a geometry network.

  • Alembic Group

    Creates a geometry group for Alembic primitives.

  • Alembic Primitive

    Modifies intrinsic properties of Alembic primitives.

  • Alembic ROP output driver

  • Align

    Aligns a group of primitives to each other or to an auxiliary input.

  • Assemble

    Cleans up a series of break operations and creates the resulting pieces.

  • Attribute Blur

    Blurs out (or "relaxes") points in a mesh or a point cloud.

  • Attribute Cast

    Changes the size/precision Houdini uses to store an attribute.

  • Attribute Composite

    Composites vertex, point, primitive, and/or detail attributes between two or more selections.

  • Attribute Copy

    Copies attributes between groups of vertices, points, or primitives.

  • Attribute Create

    Adds or edits user defined attributes.

  • Attribute Delete

    Deletes point and primitive attributes.

  • Attribute Expression

    Allows simple VEX expressions to modify attributes.

  • Attribute Fade

    Fades a point attribute in and out over time.

  • Attribute Interpolate

    Interpolates attributes within primitives or based on explicit weights.

  • Attribute Mirror

    Copies and flips attributes from one side of a plane to another.

  • Attribute Noise

    Adds noise to attributes of the incoming geometry.

  • Attribute Paint

    Interactively paint point attributes, such as color or deformation mask values, directly on geometry.

  • Attribute Promote

    Promotes or demotes attributes from one geometry level to another.

  • Attribute Randomize

    Generates random attribute values of various distributions.

  • Attribute Remap

    Fits an attribute’s values to a new range.

  • Attribute Rename

    Renames or deletes point and primitive attributes.

  • Attribute Reorient

    Modifies point attributes based on differences between two models.

  • Attribute String Edit

    Edits string attribute values.

  • Attribute Swap

    Copies, moves, or swaps the contents of attributes.

  • Attribute Transfer

    Transfers vertex, point, primitive, and/or detail attributes between two models.

  • Attribute Transfer By UV

    Transfers attributes between two geometries based on UV proximity.

  • Attribute VOP

    Runs a VOP network to modify geometry attributes.

  • Attribute Wrangle

    Runs a VEX snippet to modify attribute values.

  • Attribute from Map

    Samples texture map information to a point attribute.

  • Attribute from Volume

    Copies information from a volume onto the point attributes of another piece of geometry, with optional remapping.

  • Bake ODE

    Converts primitives for ODE and Bullet solvers.

  • Bake Volume

    Computes lighting values within volume primitives

  • Basis

    Provides operations for moving knots within the parametric space of a NURBS curve or surface.

  • Bend

    Applies captures such as bend, twist, taper, and squash/stretch.

  • Blast

    Deletes primitives, points, edges or breakpoints.

  • Blend Shapes

    Computes a 3D metamorphosis between shapes with the same topology.

  • Block Begin

    The start of a looping block.

  • Block Begin Compile

    The start of a compile block.

  • Block End

    The end/output of a looping block.

  • Block End Compile

    The end/output of a compile block.

  • Bone Capture

    Supports Bone Deform by assigning capture weights to bones.

  • Bone Capture Biharmonic

    Supports Bone Deform by assigning capture weights to points based on biharmonic functions on tetrahedral meshes.

  • Bone Capture Lines

    Utility node that supports Bone Capture Biharmonic by creating lines from bones with suitable attributes.

  • Bone Capture Proximity

    Supports Bone Deform by assigning capture weights to points based on distance to bones.

  • Bone Deform

    Uses capture attributes created from bones to deform geometry according to their movement.

  • Bone Link

    Creates default geometry for Bone objects.

  • Boolean

    Combines two polygonal objects with boolean operators, or finds the intersection lines between two polygonal objects.

  • Boolean Fracture

    Fractures the input geometry using cutting surfaces.

  • Bound

    Creates a bounding box, sphere, or rectangle for the input geometry.

  • Box

    Creates a cube or six-sided rectangular box.

  • Bulge

    Deforms the points in the first input using one or more magnets from the second input.

  • COP2 Network

    Imports 2d geometry from a Composite network.

  • Cache

    Records and caches its input geometry for faster playback.

  • Cap

    Closes open areas with flat or rounded coverings.

  • Capture Attribute Pack

    Converts array attributes into a single index-pair capture attribute.

  • Capture Attribute Unpack

    Converts a single index-pair capture attribute into per-point and detail array attributes.

  • Capture Correct

    Adjusts capture regions and capture weights.

  • Capture Layer Paint

    Lets you paint capture attributes directly onto geometry.

  • Capture Mirror

    Copies capture attributes from one half of a symmetric model to the other.

  • Capture Override

    Overrides the capture weights on individual points.

  • Capture Region

    Supports Capture and Deform operation by creating a volume within which points are captured to a bone.

  • Carve

    Slices, cuts or extracts points or cross-sections from a primitive.

  • Channel

    Reads sample data from a chop and converts it into point positions and point attributes.

  • Circle

    Creates open or closed arcs, circles and ellipses.

  • Circle from Edges

    Transforms selected geometry into a circle.

  • Clay

    Lets you deform NURBS faces and NURBS surfaces by pulling points that lie directly on them.

  • Clean

    Helps clean up dirty models.

  • Clip

    Removes or groups geometry on one side of a plane, or creases geometry along a plane.

  • Cloth Capture

    Captures low-res simulated cloth.

  • Cloth Deform

    Deforms geometry captured by the Cloth Capture SOP.

  • Cloud

    Creates a volume representation of source geometry.

  • Cloud Light

    Fills a volume with a diffuse light.

  • Cloud Noise

    Applies a cloud like noise to a Fog volume.

  • Cluster

    Low-level machinery to cluster points based on their positions (or any vector attribute).

  • Cluster Points

    Higher-level node to cluster points based on their positions (or any vector attribute).

  • Collision Source

    Creates geometry and VDB volumes for use with DOPs collisions.

  • Color

    Adds color attributes to geometry.

  • Comb

    Adjust surface point normals by painting.

  • Connect Adjacent Pieces

    Creates lines between nearby pieces.

  • Connectivity

    Creates an attribute with a unique value for each set of connected primitives or points.

  • Control

    Creates simple geometry for use as control shapes.

  • Convert

    Converts geometry from one geometry type to another.

  • Convert HeightField

    Converts a 2D height field to a 3D VDB volume, polygon surface, or polygon soup surface.

  • Convert Line

    Converts the input geometry into line segments.

  • Convert Meta

    Polygonizes metaball geometry.

  • Convert Tets

    Generates the oriented surface of a tetrahedron mesh.

  • Convert VDB

    Converts sparse volumes.

  • Convert VDB Points

    Converts a Point Cloud into a VDB Points Primitive, or vice versa.

  • Convert Volume

    Converts the iso-surface of a volume into a polygonal surface.

  • Convex Decomposition

    Decomposes the input geometry into approximate convex segments.

  • Copy Stamp

    Creates multiple copies of the input geometry, or copies the geometry onto the points of the second input.

  • Copy and Transform

    Copies geometry and applies transformations to the copies.

  • Copy to Curves

    Copies geometry in the first input onto curves of the second input.

  • Copy to Points

    Copies geometry in the first input onto the points of the second input.

  • Crease

    Manually adds or removes a creaseweight attribute to/from polygon edges, for use with the Subdivide SOP.

  • Creep

    Deforms and animates a piece of geometry across a surface.

  • Cross Section Surface

    Creates a surface around cross sections.

  • Crowd Source

    Populates a crowd of agent primitives.

  • Curve

    Creates polygonal, NURBS, or Bezier curves.

  • Curveclay

    Deforms a spline surface by reshaping a curve on the surface.

  • Curvesect

    Finds the intersections (or points of minimum distance) between two or more curves or faces.

  • DOP I/O

    Imports fields from DOP simulations, saves them to disk, and loads them back again.

  • DOP Import Fields

    Imports scalar and vector fields from a DOP simulation.

  • DOP Import Records

    Imports option and record data from DOP simulations into points with point attributes.

  • DOP Network

  • Debris Source

    Generates point emission sources for debris from separating fractured rigid body objects.

  • Deformation Wrangle

    Runs a VEX snippet to deform geometry.

  • Delete

    Deletes input geometry by group, entity number, bounding volume, primitive/point/edge normals, and/or degeneracy.

  • DeltaMush

    Smooths out (or "relaxes") point deformations.

  • Detangle

    Attempts to prevent collisions when deforming geometry.

  • Dissolve

    Deletes edges from the input polygonal geometry merging polygons with shared edges.

  • Distance Along Geometry

    Measures the distance of the shortest path along the geometry’s edges or surfaces from each start point.

  • Distance from Geometry

    Measures distance between each point and a reference geometry.

  • Distance from Target

    Measures distance of each point from a target.

  • Divide

    Divides, smooths, and triangulates polygons.

  • Dop Import

    Imports and transforms geometry based on information extracted from a DOP simulation.

  • Draw Curve

    Creates a curve based on user input in the viewport.

  • Draw Guides

  • Each

    Culls the input geometry according to the specifications of the For Each SOP.

  • Edge Collapse

    Collapses edges and faces to their centerpoints.

  • Edge Cusp

    Sharpens edges by uniquing their points and recomputing point normals.

  • Edge Divide

    Inserts points on the edges of polygons and optionally connects them.

  • Edge Equalize

    Transforms selected edges so that all edges are of equal length.

  • Edge Flip

    Flips the direction of polygon edges.

  • Edge Fracture

    Cuts geometry along edges using guiding curves.

  • Edge Straighten

    Straightens selected edges.

  • Edge Transport

    Copies and optionally modifies attribute values along edges networks and curves.

  • Edit

    Edits points, edges, or faces interactively.

  • Ends

    Closes, opens, or clamps end points.

  • Enumerate

    Sets an attribute on selected points or primitives to sequential numbers or strings.

  • Error

    Generates a message, warning, or error, which can show up on a parent asset.

  • Exploded View

    Pushes geometry out from the center to create an exploded view.

  • Export Object Transforms

    Export transform attributes to object nodes.

  • Extract Centroid

    Computes the centroid of each piece of the geometry.

  • Extract Transform

    Computes the best-fit transform between two pieces of geometry.

  • Extrude

    Extrudes geometry along a normal.

  • Extrude Volume

    Extrudes surface geometry into a volume.

  • FEM Visualization

  • FLIP Source

    Creates a surface or density VDB for sourcing FLIP simulations.

  • Facet

    Controls the smoothness of faceting of a surface.

  • Filament Advect

    Evolves polygonal curves as vortex filaments.

  • File

    Reads, writes, or caches geometry on disk.

  • File Cache

    Writes and reads geometry sequences to disk.

  • File Merge

    Reads and collates data from disk.

  • Fillet

    Creates smooth bridging geometry between two curves or surfaces.

  • Filmbox FBX ROP output driver

  • Find Shortest Path

    Finds the shortest paths from start points to end points, following the edges of a surface.

  • Fit

    Fits a spline curve to points, or a spline surface to a mesh of points.

  • Fluid Compress

    Compresses the output of fluid simulations to decrease size on disk

  • Font

    Creates 3D text from Type 1, TrueType and OpenType fonts.

  • Force

    Uses a metaball to attract or repel points or springs.

  • Fractal

    Creates jagged mountain-like divisions of the input geometry.

  • Fur

    Creates a set of hair-like curves across a surface.

  • Fuse

    Merges points.

  • Geometry nodes

    Geometry nodes live inside Geo objects and generate geometry.

  • Glue Cluster

    Adds strength to a glue constraint network according to cluster values.

  • Grain Source

    Generates particles to be used as sources in a particle-based grain simulation.

  • Graph Color

    Assigns a unique integer attribute to non-touching components.

  • Grid

    Creates planar geometry.

  • Groom Blend

    Blends the guides and skin of two grooms.

  • Groom Fetch

    Fetches groom data from grooming objects.

  • Groom Pack

    Packs the components of a groom into a set of named Packed Primitives for the purpose of writing it to disk.

  • Groom Switch

    Switches between all components of two groom streams.

  • Groom Unpack

    Unpacks the components of a groom from a packed groom.

  • Group

    Generates groups of points, primitives, edges, or vertices according to various criteria.

  • Group Combine

    Combines point groups, primitive groups, or edge groups according to boolean operations.

  • Group Copy

    Copies groups between two pieces of geometry, based on point/primitive numbers.

  • Group Delete

    Deletes groups of points, primitives, edges, or vertices according to patterns.

  • Group Expand

    Expands or shrinks groups of Edges, Points, Primitives, or Vertices.

  • Group Expression

    Runs VEX expressions to modify group membership.

  • Group Find Path

    Constructs groups for paths between elements.

  • Group Paint

    Sets group membership interactively by painting.

  • Group Promote

    Converts point, primitive, edge, or vertex groups into point, primitive, edge, or vertex groups.

  • Group Range

    Groups points and primitives by ranges.

  • Group Rename

    Renames groups according to patterns.

  • Group Transfer

    Transfers groups between two pieces of geometry, based on proximity.

  • Group by Lasso

    Groups points and primitives by lasso.

  • Group from Attribute Boundary

    Creates a group that includes the boundaries of the specified attribute.

  • Guide Advect

    Advects guide points through a velocity volume.

  • Guide Collide With VDB

    Resolves collisions of guide curves with VDB signed distance fields.

  • Guide Deform

    Deforms geometry with an animated skin and optionally guide curves.

  • Guide Groom

    Allows intuitive manipulation of guide curves in the viewport.

  • Guide Group

    Creates standard primitive groups used by grooming tools.

  • Guide Initialize

    Quickly give hair guides some initial direction.

  • Guide Mask

    Creates masking attributes for other grooming operations.

  • Guide Partition

    Creates and prepares parting lines for use with hair generation.

  • Guide Skin Attribute Lookup

    Looks up skin geometry attributes under the root point of guide curves.

  • Guide Tangent Space

    Constructs a coherent tangent space along a curve.

  • Guide Transfer

    Transfer hair guides between geometries.

  • Hair Card Generate

    Converts dense hair curves to a polygon card, keeping the style and shape of the groom.

  • Hair Clump

    Clumps guide curves together.

  • Hair Generate

    Generates hair on a surface or from points.

  • Hair Growth Field

    Generates a velocity field based on stroke primitives.

  • HeightField

    Generates an initial heightfield volume for use with terrain tools.

  • HeightField Blur

    Blurs a terrain height field or mask.

  • HeightField Clip

    Limits height values to a certain minimum and/or maximum.

  • HeightField Copy Layer

    Creates a copy of a height field or mask.

  • HeightField Crop

    Extracts a square of a certain width/length from a larger height volume, or resizes/moves the boundaries of the height field.

  • HeightField Cutout by Object

    Creates a cutout on a terrain based on geometry.

  • HeightField Distort by Layer

    Displaces a height field by another field.

  • HeightField Distort by Noise

    Advects the input volume through a noise pattern to break up hard edges and add variety.

  • HeightField Draw Mask

    Lets you draw shapes to create a mask for height field tools.

  • HeightField Erode

    Calculates thermal and hydraulic erosion over time (frames) to create more realistic terrain.

  • HeightField Erode Hydro

    Simulates the erosion from one heightfield sliding over another for a short time.

  • HeightField Erode Precipitation

    Distributes water along a heightfield. Offers controls for adjusting the intensity, variability, and location of rainfall.

  • HeightField Erode Thermal

    Calculates the effect of thermal erosion on terrain for a short time.

  • HeightField File

    Imports a 2D image map from a file or compositing node into a height field or mask.

  • HeightField Flow Field

    Generates flow and flow direction layers according to the input height layer.

  • HeightField Isolate Layer

    Copies another layer over the mask layer, and optionally flattens the height field.

  • HeightField Layer

    Composites together two height fields.

  • HeightField Layer Clear

    Sets all values in a heightfield layer to a fixed value.

  • HeightField Layer Property

    Sets the border voxel policy on a height field volume.

  • HeightField Mask by Feature

    Creates a mask based on different features of the height layer.

  • HeightField Mask by Object

    Creates a mask based some other geometry.

  • HeightField Mask by Occlusion

    Creates a mask where the input terrain is hollow/depressed, for example riverbeds and valleys.

  • HeightField Noise

    Adds vertical noise to a height field, creating peaks and valleys.

  • HeightField Output

    Exports height and/or mask layers to disk as an image.

  • HeightField Paint

    Lets you paint values into a height or mask field using strokes.

  • HeightField Patch

    Patches features from one heightfield to another.

  • HeightField Pattern

    Adds displacement in the form of a ramps, steps, stripes, Voronoi cells, or other patterns.

  • HeightField Project

    Projects 3D geometry into a height field.

  • HeightField Quick Shade

    Applies a material that lets you plug in textures for different layers.

  • HeightField Remap

    Remaps the values in a height field or mask layer.

  • HeightField Resample

    Changes the resolution of a height field.

  • HeightField Scatter

    Scatters points across the surface of a height field.

  • HeightField Slump

    Simulates loose material sliding down inclines and piling at the bottom.

  • HeightField Terrace

    Creates stepped plains from slopes in the terrain.

  • HeightField Tile Splice

    Stitches height field tiles back together.

  • HeightField Tile Split

    Splits a height field volume into rows and columns.

  • HeightField Transform

    Height field specific scales and offsets.

  • HeightField Visualize

    Visualizes elevations using a custom ramp material, and mask layers using tint colors.

  • Hole

    Makes holes in surfaces.

  • Inflate

    Deforms the points in the first input to make room for the inflation tool.

  • Instance

    Instances Geometry on Points.

  • Intersection Analysis

    Creates points with attributes at intersections between a triangle and/or curve mesh with itself, or with an optional second set of triangles and/or curves.

  • Intersection Stitch

    Composes triangle surfaces and curves together into a single connected mesh.

  • Invoke Compiled Block

    Processes its inputs using the operation of a referenced compiled block.

  • IsoOffset

    Builds an offset surface from geometry.

  • IsoSurface

    Generates an isometric surface from an implicit function.

  • Join

    The Join op connects a sequence of faces or surfaces into a single primitive that inherits their attributes.

  • Knife

    Divides, deletes, or groups geometry based on an interactively drawn line.

  • L-System

    Creates fractal geometry from the recursive application of simple rules.

  • Lattice

    Deforms geometry based on how you reshape control geometry.

  • Lidar Import

    Reads a lidar file and imports a point cloud from its data.

  • Line

    Creates polygon or NURBS lines from a position, direction, and distance.

  • MDD

    Animates points using an MDD file.

  • Magnet

    Deforms geometry by using another piece of geometry to attract or repel points.

  • Match Axis

    Aligns the input geometry to a specific axis.

  • Match Size

    Resizes and recenters the geometry according to reference geometry.

  • Match Topology

    Reorders the primitive and point numbers of the input geometry to match some reference geometry.

  • Material

    Assigns one or more materials to geometry.

  • Measure

    Measures area, volume, or curvature of individual elements or larger pieces of a geometry and puts the results in attributes.

  • Merge

    Merges geometry from its inputs.

  • MetaGroups

    Defines groupings of metaballs so that separate groupings are treated as separate surfaces when merged.

  • Metaball

    Creates metaballs and meta-superquadric surfaces.

  • Mirror

    Duplicates and mirrors geometry across a mirror plane.

  • Mountain

    Displaces points along their normals based on fractal noise.

  • Muscle Capture

    Supports Muscle Deform by assigning capture weights to points based on distance away from given primitives

  • Muscle Deform

    Deforms a surface mesh representing skin to envelop or drape over geometry representing muscles

  • Name

    Creates a "naming" attribute on points or primitives allowing you to refer to them easily, similar to groups.

  • Normal

    Computes surface normal attribute.

  • Null

    Does nothing.

  • Object Merge

    Merges geometry from multiple sources and allows you to define the manner in which they are grouped together and transformed.

  • Object_musclerig@musclerigstrokebuilder

  • Object_riggedmuscle@musclestrokebuilder

    Assists the creation of a Muscle or Muscle Rig by allowing you to draw a stroke on a projection surface.

  • Ocean Evaluate

    Deforms input geometry based on ocean "spectrum" volumes.

  • Ocean Foam

    Generates particle-based foam

  • Ocean Source

    Generates particles and volumes from ocean "spectrum" volumes for use in simulations

  • Ocean Spectrum

    Generates volumes containing information for simulating ocean waves.

  • Ocean Waves

    Instances individual waveforms onto input points and generated points.

  • OpenCL

    Executes an OpenCL kernel on geometry.

  • Orientation Along Curve

    Computes orientations (frames) along curves.

  • Output

    Marks the output of a sub-network.

  • Pack

    Packs geometry into an embedded primitive.

  • Pack Points

    Packs points into a tiled grid of packed primitives.

  • Packed Disk Edit

    Editing Packed Disk Primitives.

  • Packed Edit

    Editing Packed Primitives.

  • Paint Color Volume

    Creates a color volume based on drawn curve

  • Paint Fog Volume

    Creates a fog volume based on drawn curve

  • Paint SDF Volume

    Creates an SDF volume based on drawn curve

  • Particle Fluid Surface

    Generates a surface around the particles from a particle fluid simulation.

  • Particle Fluid Tank

    Creates a set of regular points filling a tank.

  • Partition

    Places points and primitives into groups based on a user-supplied rule.

  • Path Deform

    Deforms geometry using the shape of a curve.

  • Peak

    Moves primitives, points, edges or breakpoints along their normals.

  • Planar Patch

    Creates a planar polygonal patch.

  • Planar Patch from Curves

    Fills in a 2d curve network with triangles.

  • Planar Pleat

    Deforms flat geometry into a pleat.

  • Platonic Solids

    Creates platonic solids of different types.

  • Point Cloud Iso

    Constructs an iso surface from its input points.

  • Point Deform

    Deforms geometry on an arbitrary connected point mesh.

  • Point Generate

    Creates new points, optionally based on point positions in the input geometry.

  • Point Jitter

    Jitters points in random directions.

  • Point Relax

    Moves points with overlapping radii away from each other, optionally on a surface.

  • Point Replicate

    Generates a cloud of points around the input points.

  • Point Split

    Splits points shared by multiple vertices, optionally only if the vertices differ in attribute values.

  • Point Velocity

    Computes and manipulates velocities for points of a geometry.

  • Point Weld

    Merges points interactively.

  • Points from Volume

    Creates set of regular points filling a volume.

  • Poly Bridge

    Creates flat or tube-shaped polygon surfaces between source and destination edge loops, with controls for the shape of the bridge.

  • Poly Expand 2D

    Creates offset polygonal geometry for planar polygonal graphs.

  • Poly Extrude

    Extrudes polygonal faces and edges.

  • PolyBevel

    Creates straight, rounded, or custom fillets along edges and corners.

  • PolyCut

    Breaks curves where an attribute crosses a threshold.

  • PolyDoctor

    Helps repair invalid polygonal geometry, such as for cloth simulation.

  • PolyFill

    Fills holes with polygonal patches.

  • PolyFrame

    Creates coordinate frame attributes for points and vertices.

  • PolyLoft

    Creates new polygons using existing points.

  • PolyPatch

    Creates a smooth polygonal patch from primitives.

  • PolyPath

    Cleans up topology of polygon curves.

  • PolyReduce

    Reduces the number of polygons in a model while retaining its shape. This node preserves features, attributes, textures, and quads during reduction.

  • PolySoup

    Combines polygons into a single primitive that can be more efficient for many polygons

  • PolySpline

    The PolySpline SOP fits a spline curve to a polygon or hull and outputs a polygonal approximation of that spline.

  • PolySplit

    Divides an existing polygon into multiple new polygons.

  • PolyWire

    Constructs polygonal tubes around polylines, creating renderable geometry with smooth bends and intersections.

  • Pose-Space Deform

    Interpolates between a set of pose-shapes based on the value of a set of drivers.

  • Pose-Space Deform Combine

    Combine result of Pose-Space Deform with rest geometry.

  • Pose-Space Edit

    Packs geometry edits for pose-space deformation.

  • Pose-Space Edit Configure

    Creates common attributes used by the Pose-Space Edit SOP.

  • Primitive

    Edits primitive, primitive attributes, and profile curves.

  • Profile

    Extracts or manipulates profile curves.

  • Project

    Creates profile curves on surfaces.

  • Pyro Post-Process

    Applies common post-processing effects to the results of Pyro solves.

  • Pyro Solver

    Runs a dynamic Pyro simulation.

  • Pyro Source

    Creates points for sourcing pyro and smoke simulations.

  • Pyro Source Spread

    Pyro Source Spread solves for the spreading of flame across a point cloud.

  • Python

    Runs a Python snippet to modify the incoming geometry.

  • RBD Bullet Solver

    Runs a dynamic Bullet simulation.

  • RBD Cluster

    Combines fractured pieces or constraints into larger clusters.

  • RBD Configure

    Packs and creates attributes describing rigid body objects.

  • RBD Connected Faces

    Stores the primitive number and distance to the opposite face on the inside faces of fractured geometry.

  • RBD Constraint Properties

    Creates attributes describing rigid body constraints.

  • RBD Constraints From Curves

    Creates rigid body constraint geometry from curves drawn in the viewport.

  • RBD Constraints From Lines

    Creates rigid body constraint geometry from interactively drawn lines in the viewport.

  • RBD Constraints From Rules

    Creates rigid body constraint geometry from a set of rules and conditions.

  • RBD Convert Constraints

    Converts existing constraint prims into constraints with different anchor positions.

  • RBD Deform Pieces

    Deforms geometry with simulated proxy geometry.

  • RBD Disconnected Faces

    Detects when connected faces have become separated.

  • RBD Exploded View

    Merges RBD fractured geometry with the proxy geometry and pushes it out from the center to create an exploded view.

  • RBD I/O

    Packs RBD fractured geometry, saves them to disk, and loads them back again.

  • RBD Interior Detail

    Creates additional detail on the interior surfaces of fractured geometry.

  • RBD Material Fracture

    Fractures the input geometry based on a material type.

  • RBD Pack

    Packs RBD geometry, constraints, and proxy geometry into a single geometry.

  • RBD Paint

    Paints values onto geometry or constraints using strokes.

  • RBD Unpack

    Unpacks an RBD setup into three outputs.

  • RMan Shader

    Attaches RenderMan shaders to groups of faces.

  • ROP Geometry Output

  • Rails

    Generates surfaces by stretching cross-sections between two guide rails.

  • Ray

    Projects one surface onto another.

  • Refine

    Increases the number of points/CVs in a curve or surface without changing its shape.

  • Reguide

    Scatters new guides, interpolating the properties of existing guides.

  • Remesh

    Recreates the shape of the input surface using "high-quality" (nearly equilateral) triangles.

  • Repack

    Repacks geometry as an embedded primitive.

  • Resample

    Resamples one or more curves or surfaces into even length segments.

  • Rest Position

    Sets the alignment of solid textures to the geometry so the texture stays put on the surface as it deforms.

  • Retime

    Retimes the time-dependent input geometry.

  • Reverse

    Reverses or cycles the vertex order of faces.

  • Revolve

    Revolves a curve around a center axis to sweep out a surface.

  • Rewire Vertices

    Rewires vertices to different points specified by an attribute.

  • Ripple

    Generates ripples by displacing points along the up direction specified.

  • Ripple

    Generates ripples by displacing points along the up direction specified.

  • Scatter

    Scatters new points randomly across a surface or through a volume.

  • Script

    Runs scripts when cooked.

  • Sculpt

    Lets you interactively reshape a surface by brushing.

  • Sequence Blend

    Morphs though a sequence of 3D shapes, interpolating geometry and attributes.

  • Shape Diff

    Computes the post-deform or pre-deform difference of two geometries with similar topologies.

  • Shrinkwrap

    Computes the convex hull of the input geometry and moves its polygons inwards along their normals.

  • Skin

    Builds a skin surface between any number of shape curves.

  • Sky

    Creates a sky filled with volumentric clouds

  • Smooth

    Smooths out (or "relaxes") polygons, meshes and curves without increasing the number of points.

  • Soft Peak

    Moves the selected point along its normal, with smooth rolloff to surrounding points.

  • Soft Transform

    Moves the selected point, with smooth rolloff to surrounding points.

  • Solid Conform

    Creates a tetrahedral mesh that conforms to a connected mesh as much as possible.

  • Solid Embed

    Creates a simple tetrahedral mesh that covers a connected mesh.

  • Solid Fracture

    Creates a partition of a tetrahedral mesh that can be used for finite-element fracturing.

  • Solver

    Allows running a SOP network iteratively over some input geometry, with the output of the network from the previous frame serving as the input for the network at the current frame.

  • Sort

    Reorders points and primitives in different ways, including randomly.

  • Sphere

    Creates a sphere or ovoid surface.

  • Split

    Splits primitives or points into two streams.

  • Spray Paint

    Spray paints random points onto a surface.

  • Sprite

    A SOP node that sets the sprite display for points.

  • Starburst

    Insets points on polygonal faces.

  • Stash

    Caches the input geometry in the node on command, and then uses it as the node’s output.

  • Stitch

    Stretches two curves or surfaces to cover a smooth area.

  • Stroke

    Low level tool for building interactive assets.

  • Subdivide

    Subdivides polygons into smoother, higher-resolution polygons.

  • Subnetwork

    The Subnet op is essentially a way of creating a macro to represent a collection of ops as a single op in the Network Editor.

  • Super Quad

    Generates an isoquadric surface.

  • Surfsect

    Trims or creates profile curves along the intersection lines between NURBS or bezier surfaces.

  • Sweep

    Creates a surface by sweeping a cross section curve along a spine curve.

  • Switch

    Switches between network branches based on an expression or keyframe animation.

  • Switch-If

    Switches between two network branches based on an expression or geometry test.

  • TOP Geometry

    Sends input geometry to a TOP subnet and retrieves the output geometry.

  • Table Import

    Reads a CSV file creating point per row.

  • Test Geometry: Crag

    Creates a rock creature, which can be used as test geometry.

  • Test Geometry: Pig Head

    Creates a pig head, which can be used as test geometry..

  • Test Geometry: Rubber Toy

    Creates a rubber toy, which can be used as test geometry.

  • Test Geometry: Shader Ball

    Creates a shader ball, which can be used to test shaders.

  • Test Geometry: Squab

    Creates a squab, which can be used as test geometry.

  • Test Geometry: Template Body

    Creates a template body, which can be used as test geometry.

  • Test Geometry: Template Head

    Creates a template head, which can be used as test geometry.

  • Test Geometry: Tommy

    Creates a soldier, which can be used as test geometry.

  • Test Simulation: Crowd Transition

    Provides a simple crowd simulation for testing transitions between animation clips.

  • Test Simulation: Ragdoll

    Provides a simple Bullet simulation for testing the behavior of a ragdoll.

  • Tet Partition

    Partitions a given tetrahedron mesh into groups of tets isolated by a given polygon mesh

  • Tetrahedralize

    Performs variations of a Delaunay Tetrahedralization.

  • TimeShift

    Cooks the input at a different time.

  • Toon Shader Attributes

    Sets attributes used by the Toon Color Shader and Toon Outline Shader.

  • Topo Transfer

    Non-rigidly deforms a surface to match the size and shape of a different surface.

  • TopoBuild

    Lets you interactively draw a reduced quad mesh automatically snapped to existing geometry.

  • Torus

    Creates a torus (doughnut) shaped surface.

  • Trace

    Traces curves from an image file.

  • Trail

    Creates trails behind points.

  • Transform

    The Transform operation transforms the source geometry in "object space" using a transformation matrix.

  • Transform Axis

    Transforms the input geometry relative to a specific axis.

  • Transform By Attribute

    Transforms the input geometry by a point attribute.

  • Transform Pieces

    Transforms input geometry according to transformation attributes on template geometry.

  • Tri Bezier

    Creates a triangular Bezier surface.

  • TriDivide

    Refines triangular meshes using various metrics.

  • Triangulate 2D

    Connects points to form well-shaped triangles.

  • Trim

    Trims away parts of a spline surface defined by a profile curve or untrims previous trims.

  • Tube

    Creates open or closed tubes, cones, or pyramids.

  • UV Autoseam

    Generates an edge group representing suggested seams for flattening a polygon model in UV space.

  • UV Brush

    Adjusts texture coordinates in the UV viewport by painting.

  • UV Edit

    Lets you interactively move UVs in the texture view.

  • UV Flatten

    Creates flattened pieces in texture space from 3D geometry.

  • UV Fuse

    Merges UVs.

  • UV Layout

    Packs UV islands efficiently into a limited area.

  • UV Pelt

    Relaxes UVs by pulling them out toward the edges of the texture area.

  • UV Project

    Assigns UVs by projecting them onto the surface from a set direction.

  • UV Quick Shade

    Applies an image file as a textured shader to a surface.

  • UV Texture

    Assigns texture UV coordinates to geometry for use in texture and bump mapping.

  • UV Transform

    Transforms UV texture coordinates on the source geometry.

  • UV Unwrap

    Separates UVs into reasonably flat, non-overlapping groups.

  • Unix

    Processes geometry using an external program.

  • Unpack

    Unpacks packed primitives.

  • Unpack Points

    Unpacks points from packed primitives.

  • Unpack USD

    Converts "packed USD" primitives into normal Houdini geometry.

  • VDB

    Creates one or more empty/uniform VDB volume primitives.

  • VDB Activate

    Activates voxel regions of a VDB for further processing.

  • VDB Activate SDF

    Expand or contract signed distance fields stored on VDB volume primitives.

  • VDB Advect

    Moves VDBs in the input geometry along a VDB velocity field.

  • VDB Advect Points

    Moves points in the input geometry along a VDB velocity field.

  • VDB Analysis

    Computes an analytic property of a VDB volumes, such as gradient or curvature.

  • VDB Clip

    Clips VDB volume primitives using a bounding box or another VDB as a mask.

  • VDB Combine

    Combines the values of two aligned VDB volumes in various ways.

  • VDB Diagnostics

    Tests VDBs for Bad Values and Repairs.

  • VDB Fracture

    Cuts level set VDB volume primitives into multiple pieces.

  • VDB LOD

    Build an LOD Pyramid from a VDB.

  • VDB Morph SDF

    Blends between source and target SDF VDBs.

  • VDB Occlusion Mask

    Create a mask of the voxels in shadow from a camera for VDB primitives.

  • VDB Points Delete

    Deletes points inside of VDB Points primitives.

  • VDB Points Group

    Manipulates the Internal Groups of a VDB Points Primitive.

  • VDB Potential Flow

    Computes the steady-state air flow around VDB obstacles.

  • VDB Project Non-Divergent

    Removes divergence from a Vector VDB.

  • VDB Renormalize SDF

    Fixes signed distance fields stored in VDB volume primitives.

  • VDB Resample

    Re-samples a VDB volume primitive into a new orientation and/or voxel size.

  • VDB Reshape SDF

    Reshapes signed distance fields in VDB volume primitives.

  • VDB Segment by Connectivity

    Splits SDF VDBs into connected components.

  • VDB Smooth

    Smooths out the values in a VDB volume primitive.

  • VDB Smooth SDF

    Smooths out SDF values in a VDB volume primitive.

  • VDB Topology to SDF

    Creates an SDF VDB based on the active set of another VDB.

  • VDB Vector Merge

    Merges three scalar VDB into one vector VDB.

  • VDB Vector Split

    Splits a vector VDB primitive into three scalar VDB primitives.

  • VDB Visualize Tree

    Replaces a VDB volume with geometry that visualizes its structure.

  • VDB from Particle Fluid

    Generates a signed distance field (SDF) VDB volume representing the surface of a set of particles from a particle fluid simulation.

  • VDB from Particles

    Converts point clouds and/or point attributes into VDB volume primitives.

  • VDB from Polygons

    Converts polygonal surfaces and/or surface attributes into VDB volume primitives.

  • VDB to Spheres

    Fills a VDB volume with adaptively-sized spheres.

  • Vellum Configure Grain

    Configures geometry for Vellum Grain constraints.

  • Vellum Constraints

    Configure constraints on geometry for the Vellum solvers.

  • Vellum Drape

    Vellum solver setup to pre-roll fabric to drape over characters.

  • Vellum I/O

    Packs Vellum simulations, saves them to disk, and loads them back again.

  • Vellum Pack

    Packs Vellum geometry and constraints into a single geometry.

  • Vellum Post-Process

    Applies common post-processing effects to the result of Vellum solves.

  • Vellum Reference Frame

    Ties vellum points to a reference frame defined by moving geometry.

  • Vellum Rest Blend

    Blends the current rest values of constraints with a rest state calculated from external geometry.

  • Vellum Solver

    Runs a dynamic Vellum simulation.

  • Vellum Unpack

    Unpacks a Vellum simulation into two outputs.

  • Verify BSDF

    Verify that a bsdf conforms to the required interface.

  • Vertex

    Manually adds or edits attributes on vertices (rather than on points).

  • Visibility

    Shows/hides primitives in the 3D viewer and UV editor.

  • Visualize

    Lets you attach visualizations to different nodes in a geometry network.

  • Volume

    Creates a volume primitive.

  • Volume Analysis

    Computes analytic properties of volumes.

  • Volume Arrival Time

    Computes a speed-defined travel time from source points to voxels.

  • Volume Blur

    Blurs the voxels of a volume.

  • Volume Bound

    Bounds voxel data.

  • Volume Break

    Cuts polygonal objects using a signed distance field volume.

  • Volume Compress

    Re-compresses Volume Primitives.

  • Volume Convolve 3×3×3

    Convolves a volume by a 3×3×3 kernel.

  • Volume FFT

    Compute the Fast Fourier Transform of volumes.

  • Volume Feather

    Feathers the edges of volumes.

  • Volume Merge

    Flattens many volumes into one volume.

  • Volume Mix

    Combines the scalar fields of volume primitives.

  • Volume Optical Flow

    Translates the motion between two "image" volumes into displacement vectors.

  • Volume Patch

    Fill in a region of a volume with features from another volume.

  • Volume Ramp

    Remaps a volume according to a ramp.

  • Volume Rasterize

    Rasterizes into a volume.

  • Volume Rasterize Attributes

    Samples point attributes into VDBs.

  • Volume Rasterize Curve

    Converts a curve into a volume.

  • Volume Rasterize Hair

    Converts fur or hair to a volume for rendering.

  • Volume Rasterize Particles

    Converts a point cloud into a volume.

  • Volume Rasterize Points

    Converts a point cloud into a volume.

  • Volume Reduce

    Reduces the values of a volume into a single number.

  • Volume Resample

    Resamples the voxels of a volume to a new resolution.

  • Volume Resize

    Resizes the bounds of a volume without changing voxels.

  • Volume SDF

    Builds a Signed Distance Field from an isocontour of a volume.

  • Volume Slice

    Extracts 2d slices from volumes.

  • Volume Splice

    Splices overlapping volume primitives together.

  • Volume Stamp

    Stamps volumes instanced on points into a single target volume.

  • Volume Surface

    Adaptively surfaces a volume hierarchy with a regular triangle mesh.

  • Volume Trail

    Computes a trail of points through a velocity volume.

  • Volume VOP

    Runs CVEX on a set of volume primitives.

  • Volume Velocity

    Computes a velocity volume.

  • Volume Velocity from Curves

    Generates a volume velocity field using curve tangents.

  • Volume Velocity from Surface

    Generates a velocity field within a surface geometry.

  • Volume Visualization

    Adjusts attributes for multi-volume visualization.

  • Volume Wrangle

    Runs a VEX snippet to modify voxel values in a volume.

  • Volume from Attribute

    Sets the voxels of a volume from point attributes.

  • Voronoi Fracture

    Fractures the input geometry by performing a Voronoi decomposition of space around the input cell points

  • Voronoi Fracture Points

    Given an object and points of impact on the object, this SOP generates a set of points that can be used as input to the Voronoi Fracture SOP to simulate fracturing the object from those impacts.

  • Voronoi Split

    Cuts the geometry into small pieces according to a set of cuts defined by polylines.

  • Vortex Force Attributes

    Creates the point attributes needed to create a Vortex Force DOP.

  • Whitewater Source

    Generates volumes to be used as sources in a whitewater simulation.

  • Winding Number

    Computes generalized winding number of surface at query points.

  • Wire Blend

    Morphs between curve shapes while maintaining curve length.

  • Wire Capture

    Captures surfaces to a wire, allowing you to edit the wire to deform the surface.

  • Wire Deform

    Deforms geometry captured to a curve via the Wire Capture node.

  • Wire Transfer

    Transfers the shape of one curve to another.

  • Wireframe

    Constructs polygonal tubes around polylines, creating renderable geometry.

  • _heightfield_common

  • _vellum_common

  • glTF ROP output driver

  • posescope

    Assigns channel paths and/or pickscripts to geometry.

  • standard_crowdsim_parms