Houdini 17.0 Nodes Dynamics nodes

RBD Solver dynamics node

Sets and configures a Rigid Body Dynamics solver.

On this page

The RBD Solver DOP sets objects to use the Rigid Body Dynamics solver.

If an object has this DOP as its "Solver" subdata, it will evolve itself as an RBD Object.

This solver makes extensive use of volumetric representations of object. It is recommended that the object’s geometry have a Volumetric Representation DOP attached to it to allow this representation to be tailored to the needs of the geometry.

This solver uses the "Position" subdata, which it expects to be the type generated by a Motion DOP or Position DOP.

The Stack solver requires a total number of passes equal to Collision Passes + (Contact Passes + Shock Propagation) * SubContact Passes.

Notes

  • RBD simulation processes all collisions at the start of the time step rather than at the exact time that the collision occurs. This simplifies complicated interactions, but can result in visual artifacts. A fast moving object may appear to bounce back from a surface before it reaches it, for example, as the impulse from hitting the surface is applied to the objects position at the start of the time step.

    Increasing substepping will reduce these artifacts by ensuring the object is closer to the surface when the collision is detected.

  • Increase substepping if objects move large distances within a single frame. An object should move less than half of its smallest important feature in a single step to avoid temporal aliasing problems.

    Increase the Maximum Substeps to allow the automatic substep calculation to determine the right substepping to avoid temporal aliasing. This is a function of the velocity of your objects and the resolution of the volume representation of those objects. It is then scaled by the CFL condition - a smaller CFL condition will result in more substeps.

    Increasing the Minimum Substeps can ensure that the substepping never takes fewer than the given number of substeps. This is required if deforming collision geometry is used because the collision geometry is not taken into account in the automatic sub step computation.

Parameters

Collision Passes

The stack solver iterates over all objects looking for ballistic collisions. Because resolving one collision may create a collision elsewhere, this cannot be resolved in a single pass with a local solution.

The stack solver will thus repeat the collision resolution until either no collisions are found, or this pass count is reached.

Even if a collision is not fully resolved with these passes, it will still be cleaned up in the Contact Pass. The main difference is that it will become inelastic.

Contact Passes

The stack solver iterates over all objects, looking for cases where resting contact requires an acceleration to be adjusted.

Multiply stacked objects are common, so this often has complicated interrelationships, so requires multiple passes to converge.

SubContact Passes

Resting objects have a higher stability requirement than bouncing objects. Thus, the object is not immediately brought to a standstill, but slowed over multiple iterations to allow the system to stabilize.

This is the number of steps to do this for every contact pass.

Shock Propagation

These passes are very similar to Contact Passes.

The main difference is that if a book were resting on a table, the table would be assigned infinite mass in this pass. This prevents the table from shifting into the ground, allowing the system to converge faster.

As a rule of thumb, set this to the expected maximum number of stacked objects. If you plane to have ten tables stacked on top of one another in a stable configuration, a value of 10 can help ensure that the stacking is fully resolved.

If your objects come to rest appropriately, but then seem to slowly start to sink through each other, increasing Shock Propagation can be the right answer.

Resolve Penetrations

These passes are a final attempt to prevent any interpenetration. Like Shock Propagation, it is attempted to process objects from bottom up.

If a book is resting on a table and is penetrating the table, the book will be moved to lie outside of the table. This will be performed even if the book is at rest on the table.

The penetration recover repeated until there are no more penetrations up to the maximum number provided by this parameter.

The SubContact Passes is used to slowly feather the objects apart. Rather than immediately moving the book outside of the table, it is done in over the given number of subcontact passes. This is done to attempt to stabilize the process when complicated overlaps occur.

Use Point Velocity for Collisions

Determines if changes in the point positions will be used in collision resolution. Note that this is different from the Inherit Velocity option of RBD State. This flag only governs if velocity attributes are used for collisions, not for setting up the initial velocities.

When this is set, the object is inspected for any per point velocity attribute. If present, it is assumed to be a local deformation vector and is used to improve collision response.

If no point velocities are present, the geometry is compared between the two frames to manually calculate the per-point velocity. Note that if your deformation is a function of $F you may not get expected results as that is a step function, use $FF instead.

Use Volume Velocity for Collisions

Determines if changes to the volumetric representation will be used in collision resolution.

When this is set the volumetric representation is compared between this frame and the previous frame. The difference is used to compute a velocity of the surface’s deformation. This allows deforming objects to interact plausibly.

Note

This method can handle changing topologies, but cannot

discover tangential deformational velocities.

Glue Ignores Resting Objects

When objects are resting on top of one another, they still receive impacts due to the force of gravity. This option prevents these from being added to the glue impulse, making it easier to prevent things from falling apart under their own gravity.

Add Impact Data

During the RBD solving process, numerous impacts are calculated between the RBD objects. These are normally not recorded in order to save time.

If this is set, however, all such impacts will be recorded by attaching an Impacts/RBDImpacts data to the objects that collide.

Culling Method

In simulations with a large number of objects, it is helpful to use various space partitioning schemes to reduce the work in finding collisions. This option selects one of these schemes.

None means that no attempt at spatial subdivision will occur.

Sphere means the objects will be treated as spheres and trivial intersection detection will be done with these spheres. This is fast, but with long skinny objects could cause false positives.

OBB means Oriented Bounding Boxes. While this provides a tight bound on long skinny objects, building the spatial partitioning tree is slow and will often exceed the benefits.

Contact Grouping Method

Controls whether and how Houdini groups similar points together when it calculates point collisions.

If you set this parameter to a value other than "none", Houdini will treat similar points (that is, points within the distance specified in the Contact grouping tolerance below) as a single point for the purpose of calculating collisions.

This is useful when you have an object such as a cube, where the geometry points (the corners of the cube) are spaced far apart. One corner might impact a ground plane first, then the cube bounces and rotates so the opposite corner hits, which bounces and rotates, causing jitter when the cube hits.

If you set the Contact Grouping Method to "Average", Houdini will calculate the hit based on an average point between the corners, giving a more stable result with less jitter.

This is similar to the effect of turning on Edge representation in the Surface tab of an RBD Object node. If you have sparse geometry with sharp edges, such as a cube, you may want to turn on both these options.

To see the effect of contact groupings, create a simulation where you drop a cube onto a ground plane. Attach an RBD Visualization DOP to see the resulting impacts.

None

Calculate collisions for each point independently. Do not attempt to merge similar collision points.

Most central point

Group similar points together as the one point that is most in-line with the center of mass of the object. This uses only points from the original geometry and biases collision points to stable points.

Average point

Average similar points together to calculate the collision point.

This reflects the geometry of the actual collision better than "Most central point", but may result in a point that does not lie on the original geometry.

Contact Grouping Tolerance

The distance within which points are grouped together when Contact grouping method is not "none".

Minimum Substeps

The RBD Solver will break a full timestep into at least this number of substeps.

By increasing this, you can guarantee a minimum fineness to the substepping. This can be used if for some reason the automatic computations are too coarse.

Maximum Substeps

The RBD Solver will not break the simulation down into more substeps than this.

It is a very good idea to always have a maximum to ensure frames will be finished regardless of their complexity. Lowering this ceiling can ensure a minimum computation time at the expense of accuracy.

CFL Condition

The CFL Condition is a factor used for automatically determining what size substep a scene requires. The idea is that any substep should not allow any objects to interpenetrate by more than one voxel cell.

This condition is met when this parameter is at 1. A value of 10 would allow a substep to interpenetrate by as many as 10 voxel cells. This could allow objects to tunnel through each other rather than properly bounce.

Parameter Operations

Each data option parameter has an associated menu which specifies how that parameter operates.

Use Default

Use the value from the Default Operation menu.

Set Initial

Set the value of this parameter only when this data is created. On all subsequent timesteps, the value of this parameter is not altered. This is useful for setting up initial conditions like position and velocity.

Set Always

Always set the value of this parameter. This is useful when specific keyframed values are required over time. This could be used to keyframe the position of an object over time, or to cause the geometry from a SOP to be refetched at each timestep if the geometry is deforming.

You can also use this setting in conjunction with the local variables for a parameter value to modify a value over time. For example, in the X Position, an expression like $tx + 0.1 would cause the object to move 0.1 units to the right on each timestep.

Set Never

Do not ever set the value of this parameter. This option is most useful when using this node to modify an existing piece of data connected through the first input.

For example, an RBD State DOP may want to animate just the mass of an object, and nothing else. The Set Never option could be used on all parameters except for Mass, which would use Set Always.

Default Operation

For any parameters with their Operation menu set to Use Default, this parameter controls what operation is used.

This parameter has the same menu options and meanings as the Parameter Operations menus, but without the Use Default choice.

Make Objects Mutual Affectors

All objects connected to the first input of this node become mutual affectors.

This is equivalent to using an Affector DOP to create an affector relationship between * and * before connecting it to this node. This option makes it convenient to have all objects feeding into a solver node affect each other.

Group

When an object connector is attached to the first input of this node, this parameter can be used to choose a subset of those objects to be affected by this node.

Data Name

Indicates the name that should be used to attach the data to an object or other piece of data. If the Data Name contains a "/" (or several), that indicates traversing inside subdata.

For example, if the Fan Force DOP has the default Data Name "Forces/Fan". This attaches the data with the name "Fan" to an existing piece of data named "Forces". If no data named "Forces" exists, a simple piece of container data is created to hold the "Fan" subdata.

Different pieces of data have different requirements on what names should be used for them. Except in very rare situations, the default value should be used. Some exceptions are described with particular pieces of data or with solvers that make use of some particular type of data.

Unique Data Name

Turning on this parameter modifies the Data Name parameter value to ensure that the data created by this node is attached with a unique name so it will not overwrite any existing data.

With this parameter turned off, attaching two pieces of data with the same name will cause the second one to replace the first. There are situations where each type of behavior is desirable.

If an object needs to have several Fan Forces blowing on it, it is much easier to use the Unique Data Name feature to ensure that each fan does not overwrite a previous fan rather than trying to change the Data Name of each fan individually to avoid conflicts.

On the other hand, if an object is known to have RBD State data already attached to it, leaving this option turned off will allow some new RBD State data to overwrite the existing data.

Solver Per Object

The default behavior for solvers is to attach the exact same solver to all of the objects specified in the group. This allows the objects to be processed in a single pass by the solver, since the parameters are identical for each object. However, some objects operate more logically on a single object at a time. In these cases, one may want to use $OBJID expressions to vary the solver parameters across the objects. Setting this toggle will create a separate solver per object, allowing $OBJID to vary as expected.

Inputs

First Input

This optional input can be used to control which simulation objects are modified by this node. Any objects connected through this input and which match the Group parameter field will be modified.

If this input is not connected, this node can be used in conjunction with an Apply Data node, or can be used as an input to another data node.

All Other Inputs

If this node has more input connectors, other data nodes can be attached to act as modifiers for the data created by this node.

The specific types of subdata that are meaningful vary from node to node. Click an input connector to see a list of available data nodes that can be meaningfully attached.

Outputs

First Output

The operation of this output depends on what inputs are connected to this node. If an object stream is input to this node, the output is also an object stream containing the same objects as the input (but with the data from this node attached).

If no object stream is connected to this node, the output is a data output. This data output can be connected to an Apply Data DOP, or connected directly to a data input of another data node, to attach the data from this node to an object or another piece of data.

Locals

channelname

This DOP node defines a local variable for each channel and parameter on the Data Options page, with the same name as the channel. So for example, the node may have channels for Position (positionx, positiony, positionz) and a parameter for an object name (objectname).

Then there will also be local variables with the names positionx, positiony, positionz, and objectname. These variables will evaluate to the previous value for that parameter.

This previous value is always stored as part of the data attached to the object being processed. This is essentially a shortcut for a dopfield expression like:

dopfield($DOPNET, $OBJID, dataName, "Options", 0, channelname)

If the data does not already exist, then a value of zero or an empty string will be returned.

DATACT

This value is the simulation time (see variable ST) at which the current data was created. This value may not be the same as the current simulation time if this node is modifying existing data, rather than creating new data.

DATACF

This value is the simulation frame (see variable SF) at which the current data was created. This value may not be the same as the current simulation frame if this node is modifying existing data, rather than creating new data.

RELNAME

This value will be set only when data is being attached to a relationship (such as when Constraint Anchor DOP is connected to the second, third, of fourth inputs of a Constraint DOP).

In this case, this value is set to the name of the relationship the data to which the data is being attached.

RELOBJIDS

This value will be set only when data is being attached to a relationship (such as when Constraint Anchor DOP is connected to the second, third, of fourth inputs of a Constraint DOP).

In this case, this value is set to a string that is a space separated list of the object identifiers for all the Affected Objects of the relationship to which the data is being attached.

RELOBJNAMES

This value will be set only when data is being attached to a relationship (such as when Constraint Anchor DOP is connected to the second, third, of fourth inputs of a Constraint DOP).

In this case, this value is set to a string that is a space separated list of the names of all the Affected Objects of the relationship to which the data is being attached.

RELAFFOBJIDS

This value will be set only when data is being attached to a relationship (such as when Constraint Anchor DOP is connected to the second, third, of fourth inputs of a Constraint DOP).

In this case, this value is set to a string that is a space separated list of the object identifiers for all the Affector Objects of the relationship to which the data is being attached.

RELAFFOBJNAMES

This value will be set only when data is being attached to a relationship (such as when Constraint Anchor DOP is connected to the second, third, of fourth inputs of a Constraint DOP).

In this case, this value is set to a string that is a space separated list of the names of all the Affector Objects of the relationship to which the data is being attached.

ST

This value is the simulation time for which the node is being evaluated.

This value may not be equal to the current Houdini time represented by the variable T, depending on the settings of the DOP Network Offset Time and Time Scale parameters.

This value is guaranteed to have a value of zero at the start of a simulation, so when testing for the first timestep of a simulation, it is best to use a test like $ST == 0 rather than $T == 0 or $FF == 1.

SF

This value is the simulation frame (or more accurately, the simulation time step number) for which the node is being evaluated.

This value may not be equal to the current Houdini frame number represented by the variable F, depending on the settings of the DOP Network parameters. Instead, this value is equal to the simulation time (ST) divided by the simulation timestep size (TIMESTEP).

TIMESTEP

This value is the size of a simulation timestep. This value is useful to scale values that are expressed in units per second, but are applied on each timestep.

SFPS

This value is the inverse of the TIMESTEP value. It is the number of timesteps per second of simulation time.

SNOBJ

This is the number of objects in the simulation. For nodes that create objects such as the Empty Object node, this value will increase for each object that is evaluated.

A good way to guarantee unique object names is to use an expression like object_$SNOBJ.

NOBJ

This value is the number of objects that will be evaluated by the current node during this timestep. This value will often be different from SNOBJ, as many nodes do not process all the objects in a simulation.

This value may return 0 if the node does not process each object sequentially (such as the Group DOP).

OBJ

This value is the index of the specific object being processed by the node. This value will always run from zero to NOBJ-1 in a given timestep. This value does not identify the current object within the simulation like OBJID or OBJNAME, just the object’s position in the current order of processing.

This value is useful for generating a random number for each object, or simply splitting the objects into two or more groups to be processed in different ways. This value will be -1 if the node does not process objects sequentially (such as the Group DOP).

OBJID

This is the unique object identifier for the object being processed. Every object is assigned an integer value that is unique among all objects in the simulation for all time. Even if an object is deleted, its identifier is never reused.

The object identifier can always be used to uniquely identify a given object. This makes this variable very useful in situations where each object needs to be treated differently. It can be used to produce a unique random number for each object, for example.

This value is also the best way to look up information on an object using the dopfield expression function. This value will be -1 if the node does not process objects sequentially (such as the Group DOP).

ALLOBJIDS

This string contains a space separated list of the unique object identifiers for every object being processed by the current node.

ALLOBJNAMES

This string contains a space separated list of the names of every object being processed by the current node.

OBJCT

This value is the simulation time (see variable ST) at which the current object was created.

Therefore, to check if an object was created on the current timestep, the expression $ST == $OBJCT should always be used. This value will be zero if the node does not process objects sequentially (such as the Group DOP).

OBJCF

This value is the simulation frame (see variable SF) at which the current object was created.

This value is equivalent to using the dopsttoframe expression on the OBJCT variable. This value will be zero if the node does not process objects sequentially (such as the Group DOP).

OBJNAME

This is a string value containing the name of the object being processed.

Object names are not guaranteed to be unique within a simulation. However, if you name your objects carefully so that they are unique, the object name can be a much easier way to identify an object than the unique object identifier, OBJID.

The object name can also be used to treat a number of similar objects (with the same name) as a virtual group. If there are 20 objects named "myobject", specifying strcmp($OBJNAME, "myobject") == 0 in the activation field of a DOP will cause that DOP to operate only on those 20 objects. This value will be the empty string if the node does not process objects sequentially (such as the Group DOP).

DOPNET

This is a string value containing the full path of the current DOP Network. This value is most useful in DOP subnet digital assets where you want to know the path to the DOP Network that contains the node.

Note

Most dynamics nodes have local variables with the same names as the node’s parameters. For example, in a Position node, you could write the expression:

$tx + 0.1

…to make the object move 0.1 units along the X axis at each timestep.

Examples

DegreesOfFreedom Example for RBD Solver dynamics node

This example demonstrates the use of the Constraint Type parameter on the RBD Constraint node. This parameter controls the number of degrees of freedom the constrained object has.

PaddleWheel Example for RBD Solver dynamics node

This example combines a number of elements and features of RBD to create a simulation of a paddle wheel being hit by a large number of falling objects.

This example demonstrates features such as resolving penetrations, gluing simple objects together to create more complex objects, grouping of objects, and constraints.

The following examples include this node.

CountImpacts Example for Count channel node

This example demonstrates how to count impacts from a DOPs simulation using the Count CHOP. Then, using the values from the Count CHOP, we generate copies of a teapot.

DynamicLights Example for Dynamics channel node

This example demonstrates how to use the Dynamics CHOP to extract impact data from a DOPs simulation, and then modify the data to control lights in the scene.

DynamicPops Example for Dynamics channel node

This example demonstrates using the Dynamics CHOP to birth particles where an impact occurs, as well as controlling the birth rate based in impulse.

ExtractTransforms Example for Dynamics channel node

This example demonstrates the use of the Dynamics CHOP to pull transformation information out of a DOP simulation and apply it to Objects.

HoldLight Example for Hold channel node

This example uses the Hold CHOP in conjunction with the Dynamics CHOP to hold a light at the position of an impact from a DOPs simulation until a new impact occurs.

Lookup Example for Lookup channel node

This example demonstrates how to use the Lookup CHOP to play animation based on an event, or trigger.

AnimatedActiveState Example for Active Value dynamics node

This example shows how to use the Active Value DOP to animate the Active state of an object. When an object is not active (it is passive), it is not simulated. To keyframe both the active state of an object and its motion while passive, use the RBD Keyframe Active DOP.

AutoFreezeRBD Example for Active Value dynamics node

This example shows a system for automatically detecting when RBD objects achieve a rest state and then turning off their active status. This will freeze them in place reducing computation time and jitter.

SimpleAffector Example for Affector dynamics node

This example shows how to use the Affector DOP to set up a variety of affector relationships between a set of RBD Objects. It also shows how these different affector relationships affect the simulation.

LookAt Example for Anchor: Align Axis dynamics node

This example shows how to build a Look At Constraint which keeps a teapot pointed at a bouncing ball. It shows how to build constraints out of anchors and constraint relationships.

BridgeCollapse Example for Apply Relationship dynamics node

This example shows how to use the Apply Relationship DOP to propagate constraints automatically and create an RBD simulation of a collapsing bridge.

ConstrainedTeapots Example for Apply Relationship dynamics node

This example demonstrates how the Apply Relationship DOP can be used to create multiple constraints with the RBD Pin Constraint node.

MutualConstraints Example for Apply Relationship dynamics node

This example demonstrates how to build mutual constraints between two DOP objects using the Apply Relationship node.

SimpleBlend Example for Blend Solver dynamics node

This example demonstrates how to use the Blend Solver. In this case the Blend Solver is used to blend between an RBD solution and a keyframed solution.

BuoyancyForce Example for Buoyancy Force dynamics node

This example shows how to extract a surface field from another object to use as a buoyancy force source.

ClothAttachedDynamic Example for Cloth Object dynamics node

This example shows a piece of cloth attached to a dynamics point on a rigid object.

AutoFracturing Example for Copy Objects dynamics node

This example shows how to use the Copy Object DOP, in conjunction with a Multi Solver, to automatically break an RBD object in half whenever it impacts another object.

SimpleCopy Example for Copy Objects dynamics node

This example demonstrates the use of the Copy Objects DOP. A single RBD Object is copied 100 times, and assigned a random initial velocity, and a position based on some grid geometry. These 100 spheres are then dropped onto a ground plane.

TypesOfDrag Example for Drag Force dynamics node

This sample illustrates three different ways to apply drag on an rbd object: by dragging the linear velocity, by dragging the angular velocity, or by directly changing the angular velocity.

FromRBD Example for Field Force dynamics node

This example demonstrates how to use another active RBD Object as the source for the Field Force DOP. Two balls bounce inside a cube, one of the balls is set to repel the other according to force values stored on its geometry.

SimpleField Example for Field Force dynamics node

This example demonstrates the use of the Field Force DOP. A group of RBD Objects are passed through a field which at first pulls the together, and then pulls them apart as they advance through the field.

CacheToDisk Example for File dynamics node

This example shows how to use the File DOP to cache a simulation to disk and read it back in.

BallInTank Example for Fluid Object dynamics node

This example shows an RBD ball being thrown into a tank of liquid.

FluidFeedback Example for Fluid Object dynamics node

This example shows a ball falling into a tank with feedback. This couples the RBD simulation with the Fluid simulation, causing the ball to float rather than sink.

grass

This example simulates grass being pushed down by an RBD object. Fur Objects are used to represent the blades of grass and Wire Objects are used to simulate the motion. When a single Fur Object is used to represent the grass, neighbouring blades of grass will have similar motion. Additional objects with different stiffness values can be used to make the motion less uniform. When "Complex Mode" is enabled, two objects are used to represent the grass. The stiffness of each set of curves can be controlled by adjusting the "Angular Spring Constant" and "Linear Spring Constant" parameters on the corresponding Wire Objects.

MagnetMetaballs Example for Magnet Force dynamics node

This example demonstrates how to use the Magnet Force node on a group of metaballs to force the fragments of an object outwards at the moment of impact.

SimpleMagnets Example for Magnet Force dynamics node

This example demonstrates how the magnetforce DOP can be used with a pair of metaballs (one positive and one negative) to attract/repulse an RBD sphere.

MaskedField Example for Mask Field dynamics node

A Uniform Force is applied to a number of RBD Objects to demonstrate how the Mask Field can be used to define a region where the force will be applied.

SimpleMultiple Example for Multiple Solver dynamics node

This examples demonstrates how to use a Multiple Solver. In this example, the motion of an object is controlled by an RBD Solver while the geometry is modified by a SOP Solver.

Particle fluid buoyancy

This example demonstrates how to couple the Particle Fluid with an RBD object so they both affect each other. The result is a buoyant sphere.

DampedHinge Example for RBD Angular Spring Constraint dynamics node

This example shows how to use the RBD Angular Spring Constraint to create a damped hinge.

SimpleRotationalConstraint Example for RBD Angular Spring Constraint dynamics node

This example demonstrates the use of an RBD Angular Spring Constraint.

Stack Example for RBD Auto Freeze dynamics node

Teapots are dropped every ten frames onto a ground plane. The RBD AutoFreeze DOP is used to detect and freeze the teapots that have come to rest, stabilizing and speeding up the simulation.

StackedBricks Example for RBD Fractured Object dynamics node

This example shows how to create a large number of RBD objects from a single SOP. It also shows how a velocity point attribute can be used to set the initial motion for the objects.

BlendSolverWithRBDGlue

This example shows how to grab animated key frame data from an RBD Glue object and blend it into a simulation of a cube fragmenting into multiple pieces on impact.

ChoreographedBreakup

This example shows how one can control the break up of any glued object through the use of the RBD State node.

A torus, composed of spheres, is glued together. An additional sweep plane is defined. Any sphere which ends up on the wrong side of the sweep plane is broken off the torus and left to bounce on its own. This lets the break up of the torus to be controlled over many frames.

ChoreographedTubeBreakup

This example shows how one can control the break up of any glued object through the use of the RBD State node.

In this version of the choreographed breakup example, a moving plane is used to choreograph the breakup of a fractured tube. As the plane passes each piece, it is allowed to break off from the rest of the tube.

ShatterGlass

This example uses an RBD projectile to shatter a piece of glass. The glass is made up of simple trangular shards glued together.

This example also demonstrates a situation where using volume based collision detection would not work, and so the objects are treated as infinitely thin surfaces when performing collision detection.

Pendulum Example for RBD Hinge Constraint dynamics node

This example shows how to use the RBD Hinge Constraint to create a hinge joint between an RBD Object and a world space position or other RBD object.

SimpleKeyActive Example for RBD Keyframe Active dynamics node

This example uses the RBD Keyframe Active node to switch from a keyframed animation to an RBD Solver, and back to keyframed animation. This same animation could be created using a Switch Solver or Blend Solver, but this approach is simpler if the only requirement is switching from keyframed to simulated motion for a few RBD Objects.

DeformingRBD Example for RBD Object dynamics node

This example demonstrates a rigid body dynamics simulation involving deforming geometry. A wobbling torus is dropped onto a ground plane.

SimpleRBD Example for RBD Object dynamics node

This example demonstrates a simple rigid body dynamics simulation using the RBD Object DOP. A single sphere is dropped onto a ground plane.

Chain Example for RBD Pin Constraint dynamics node

This sample creates a chain of RBD objects connected to each other using constraints.

Pendulum Example for RBD Pin Constraint dynamics node

This example shows how to use the RBD Pin Constraint to pin RBD Objects to world space positions or other RBD objects.

popswithrbdcollision Example for RBD Point Object dynamics node

Shows an RBD Simulation being attatched to a POP simulation to provide RBD style collisions to POPs.

DegreesOfFreedom Example for RBD Solver dynamics node

This example demonstrates the use of the Constraint Type parameter on the RBD Constraint node. This parameter controls the number of degrees of freedom the constrained object has.

PaddleWheel Example for RBD Solver dynamics node

This example combines a number of elements and features of RBD to create a simulation of a paddle wheel being hit by a large number of falling objects.

This example demonstrates features such as resolving penetrations, gluing simple objects together to create more complex objects, grouping of objects, and constraints.

Weights Example for RBD Spring Constraint dynamics node

This example shows how to use the RBD Spring Constraint to create springs that will break once a threshold force or length is exceeded.

Simple Example for RBD Visualization dynamics node

This example demonstrates a simple rigid body dynamics simulation using the RBD Object DOP. A single sphere is dropped onto a ground plane. It adds in an RBD Visualization DOP to show the impact forces that are applied as a result of the collision.

ReferenceFrameForce Example for Reference Frame Force dynamics node

An RBD vase filled with water performs the water simulation in the vase’s reference frame.

Freeze Example for Script Solver dynamics node

This example uses the Script Solver to remove objects from the simulation once they fall below a certain threshold velocity. This technique can be used to speed up simulations that are known to settle down to a static arrangement.

SumImpacts Example for Script Solver dynamics node

This example uses the Script Solver and SOP Solver to change the color of RBD objects based on the total impact energy applied to the object at each timestep.

DelayedSmokeHandoff Example for Smoke Object dynamics node

This example shows a way to turn an RBD into smoke a certain number of frames after the RBD object has hit something.

RBDtoSmokeHandoff Example for Smoke Object dynamics node

This example shows a way to turn an RBD object into smoke. It uses multiple different colored smoke fields inside the same smoke object.

SourceVorticlesAndCollision Example for Smoke Object dynamics node

This example demonstrates a simple smoke system using a source, keyframed RBD collision objects, and vorticles.

rbdsmokesource Example for Smoke Object dynamics node

A ghostly tetrahedron bounces around a box, its presense shown by its continuous emission of smoke.

DentingWithPops Example for SOP Solver dynamics node

This example combines a number of important DOPs concepts.

  • First, it uses both POP Solver and RBD Solver objects interacting with each other in a bidiretional manner. The RBD object affects the particles, and the particles affect the RBD object.

  • Second, the RBD object atually uses a multi-solver to combine an RBD Solver with a SOP Solver. The RBD Solver controls the motion of the overall object, while the SOP Solver performs the denting of the geometry.

  • Third, the SOP Solver extracts impact information from the RBD Solver to perform the denting. It extracts this information using DOP expression functions.

The end result is a simulation of a torus that is bombarded by a stream of particles. The particles bounce off the torus, and also cause the torus to move. In addition, each particle collision causes a slight denting of the torus.

VisualizeImpacts Example for SOP Solver dynamics node

An example that shows how you can visualize impact data in an RBD simulation by using a SOP Solver to add custom guide geometry to the RBD Objects.

This example has three toruses falling on a grid with green lines showing the position and magnitude of impacts. The force visualization is added as ancillary geometry data to the actual toruses, so the RBD Solver is entirely unaware of the effect. The SOP Solver could also be used as an independent SOP network to extract impact visualization from an RBD Object.

SimpleVortex Example for Vortex Force dynamics node

This example uses a few balls to visualize the force generated by a Vortex Force DOP.

BeadCurtain Example for Wire Solver dynamics node

This example uses the Wire Solver to simulate a bead curtain. A stream of RBD balls are thrown at the curtain, and through feedback the curtain and balls are mutually affected by the collisions.

Pendulum Example for Wire Solver dynamics node

This example shows how to mutually affect an object at the constraint point and the object at the bob of the pendulum.

ConnectedBalls Example for Connectivity geometry node

This example demonstrates how to use an attribute generated by the Connectivity SOP to color different pieces of geometry from a DOPs simulation.

ProxyGeometry Example for Dop Import geometry node

This example demonstrates a technique of using the DOP Import SOP to allow the use of proxy geometry in a DOP simulation. One set of geometries are used in the simulation, then the transform information for those objects is applied to higher resolution versions of the geometry.

PartitionBall Example for Partition geometry node

This example demonstrates how to break geometry in a DOPs simulation using the Partition SOP to determine the DOP Objects.

Dynamics nodes