Solid Object 1.0dynamics node

Creates a Solid Object from SOP Geometry.

The Solid Object DOP creates a Solid Object inside the DOP simulation. It creates a new object and attaches the subdata required for it to be a properly conforming Solid Object. Solid Objects can be simulated using the FEM Solver.

Solid objects are different than rigid bodies. Solid objects are flexible, which makes it possible for them to deform, and can be used to simulate materials such as flesh, wood, and concrete. Solid objects are also able to break dynamically during a simulation, based on the deformation that happens during the simulation.

You can use a tetrahedral mesh in SOPs to create your solid object. Your solid geometry should satisfy guidelines that ensure a fast-running and good looking simulation.

Creating a solid object

1. Select the geometry to convert to a solid object.

2. On the Solid tab, click the Solid Object tool.

Model

Material Model

Choose the model that determines how the material resists deformation. The Neo-Hookean material model is useful for simulating biological tissues (e.g., muscles and fat), and requires the Solve Method on the FEM Solver to be set to GNL.

Shape Stiffness

This determines how strongly the Solid Object resists changes in shape. In the isotropic use case (Anisotropic Strength all 1), this physical constant is also known as shear modulus, modulus of rigidity, or Lame’s second parameter. If the units of length are set to meters, then the Shape Stiffness parameter has units of GPa.

Volume Stiffness

This determines how strongly the Solid Object resists changes in volume. In the isotropic use case (Anisotropic Strength all 1), this physical constant is also known as Lame’s first parameter. If the units of length are set to meters, then the Shape Stiffness parameter has units of GPa.

Damping Ratio

This value should lie between 0 and 1. It controls the rate of energy loss as a result of the rate of deformation. A value of 0 means that there is no loss of energy due to internal damping forces. A value of 1 means that the object is critically damped, in which case the object comes to rest in the quickest possible way without oscillating. The higher the damping ratio, the less the solid oscillates and the quicker the object’s motion will come to rest. The effect of damping is independent of your geometry’s resolution.

Mass Density

This is the mass per cubed length unit. The mass density can be made lower or higher in parts of the object using the primitive attribute `volumemassdensity`, which works as a multiplier for the parameter. The higher the mass density, the less the object tends to accelerate as a result of any internal or external forces (F = m a, Newton’s second law).

Enable Fracturing

This enables or disables all fracturing for this object.

Fracture Threshold

The amount of relative stretch that will cause the geometry to break up into separate parts during the simulation. For example, if the threshold is set to 0.1, the geometry will break in places where there is more than 10% stretch compared to the rest geometry.

Realistic solid objects are not equally strong everywhere, there are weak parts that tend to fracture before any other parts. To create these relatively weaker parts you can create a vertex attribute called `fracturethreshold`. This attribute is a multiplier for the Fracture Threshold parameter, so that you can still use the Fracture Threshold to control the overall strength of the object.

Friction Coefficient

The coefficient of friction of the object. A value of 0 means the object is frictionless. This governs how much the velocity that is tangential to the contact plane is affected by collisions. When two objects are in contact, the solver multiplies the friction coefficients of the involved object to get the effective friction coefficient for that contact.

Anisotropic Strength

These values allow you to make the internal forces of the Solid Object behave in an anisotropic way; in that case, the amount of stress will differ depending on the direction in which the object is deformed. An example of an anisotropic material is wood, which has a different strength along the grain than perpendicular to the grain. The `materialuvw` vertex or point attribute can be used to specify the internal directions of the Solid Object’s internal force model. For example, in the case of wood, the U direction could be aligned with the grain of the wood, while the VW coordinates are chosen perpendicular to the grain of the wood. In this case, the strength along the grain can be separately controlled using the U component of the Anisotropic Strength.

Geometry

Initial Geometry

This geometry determines the initial simulated state of the object. It determines the initial position and velocity for each of the points.

This is the geometry that is used for the computation of internal forces and for collision detection. Don’t use more tetrahedrons than you need to get a good looking motion; more tetrahedrons does not always translate to more quality. The fewer tetrahedrons you use, the better the simulation speed is. If extra detail needs to be added, it is recommended that you use the Embedded Geometry.

You can use the Tetrahedralize SOP to create a suitable input mesh. It is important that you enable the quality option on the Tetrahedralize SOP. Otherwise, the interior of your Solid Object won’t have enough degrees of freedom to be flexible.

Enable Embedding

Turns on/off the use of embedded geometry.

Embedded Geometry

This geometry is embedded into and deformed along with the simulated tetrahedral mesh.

Import Rest Geometry

This option allows you to specify and animate the rest positions that are used by the simulation inside the SOP network (without having to use a SOP solver). The option defines whether the rest positions should be imported from a SOP geometry node at each frame. When enabled, the solver will copy rest positions from the point attribute `restP` of the SOP geometry node onto the attribute `restP` on the simulation geometry at each frame. If no `restP` exists, then the 'P' attribute from the SOP geometry node is copied instead.

Rest Geometry Path

The path to the SOP node that will serve as the source of the rest positions.

Import Target Geometry

This option allows you to specify and animate the target positions that are used by the simulation inside the SOP network (without having to use a SOP solver). The option defines whether the target positions should be imported from a SOP geometry node at each frame. When enabled, the solver will copy target positions from the point attribute `targetP` of the SOP geometry node onto the attribute `targetP` on the simulation geometry at each frame. If no `targetP` exists, then the `P` attribute from the SOP geometry node is copied instead.

Target Geometry Path

The path to the SOP node that will serve as the source of the target positions. The positions should be stored in an attribute with the name `targetP`. If this attribute is not found, the `P` attribute is used as a fallback.

Stiffness

This coefficient determines how strongly the finite element solver tries to make the point positions match the target point positions. The solver creates an imaginary potential force for this purpose.

Damping

This coefficient determines how strongly the finite element solver tries to make the point velocities match the target point velocities. The solver creates an imaginary dissipation force for this purpose.

Fracturing

Enable Fracturing

Allows the tetrahedrons of this object to break apart when impacted beyond the force set by the Fracture threshold below. The solver must also have fracturing on (which is the default for the solver).

Fracture Threshold

The relative amount of stress in any direction above which dynamic fracturing will occur. This lets you control how quickly the object will break into pieces as a result of stresses inside the object.

Realistic objects don’t have the same fracture threshold everywhere. To achieve this, you can use a point attribute with the name `fracturethreshold` that acts as a local multiplier for the per-object fracture threshold.

It is recommended that you use the primitive attribute `fracturepart` to assign integer numbers to clumps of tetrahedrons that should never be broken up into smaller pieces. Creating these clumps prevents individual tetrahedrons from breaking off. The Solid Fracture SOP can be a useful tool for creating this `fracturepart` attribute. You can create a `fracturepart` on the embedded geometry as well. This way, the fractured pieces in the simulated geometry and the embedded geometry can be properly matched.

Collisions

Collide with objects

If enabled, the geometry in this object will collide with all other objects. These other objects may belong to the same solver or they may be be Static Objects, RBD Objects, or the Ground Plane. When the Collision Detection parameter on the Static Object is set to Use Volume Collisions, then the polygon vertices will be tested for collision against the signed distance field (SDF) of the Static Object. When Collision Detection is set to Use Surface Collisions, then geometry-based continuous collision detection is used. The geometry-based collisions collide points against polygons, and edges against edges.

When surface-based collisions are used, only polygons and tetrahedrons in the Static Object are considered. Other types of primitives, for example spheres, are be ignored. The geometry of the external objects (e.g. Static Object) is treated as being one-sided; only the outsides of the polygons, determined by the winding order, oppose collisions.

When volume-based collisions are enabled, only points will be colliding against the volumes, not the interiors of polygons and tetrahedrons. When colliding against small volumes, this may mean that you need to increase the number of points on your mesh to get accurate collision results.

Collide with other objects with same solver

When enabled, this object will collide with other objects that have the same solver. These collisions are handled using continuous collision detection, based on the geometry (polygons and/or tetrahedrons). For collisions between objects on the same solver, the polygons are treated as two-sided. Both sides of the polygons collide. The surface of a tetrahedral mesh only collides on one side: the outside.

Collide within this object

If disabled, no two tetrahedrons within this object can collide with each other.

Collide within each component

If disabled, no two tetrahedrons that belong on the same connected component may collide with each other.

Collide within each fracture part

This option only has an effect when fracturing is enabled on the solver. If disabled, no two tetrahedrons that belong on the same fracture part may collide with each other. Fracture parts are controlled by the integer-valued `fracturepart` primitive attribute.

External volume properties

Division Method

If Non Square is chosen, the specified size is divided into the given number of divisions of voxels. However, the sides of these voxels may not be equal, possibly leading to distorted simulations.

When an axis is specified, that axis is considered authoritative for determining the number of divisions. The chosen axis' size will be divided by the uniform divisions to yield the voxel size. The divisions for the other axes will then be adjusted to the closest integer multiple that fits in the required size.

Finally, the size along non-chosen axes will be changed to represent uniform voxel sizes. If the Max Axis option is chosen, the maximum sized axis is used.

When By Size is chosen, the Division Size will be used to compute the number of voxels that fit in the given sized box.

Uniform Divisions

The resolution of the key axis on the voxel grid. This allows you to control the overall resolution with one parameter and still preserve uniform voxels. The Uniform Voxels option specifies which axis should be used as the reference. It is usually safest to use the maximum axis.

Tolerance

This specifies the tolerance used for ray intersections when computing the SDF. This value is multiplied by the size of the geometry and is scale invariant.

Sign Sweep Threshold

After the fix signs process is complete there can still be inconsistent areas in the SDF. Large blocks can become stabilized and stick out of the SDF. A second sign sweep pass can be performed to try to eliminate these blocks.

The sign sweep threshold governs how big of a jump has to occur for a sign transition to be considered inconsistent. If the values of the sdf change by more than this threshold times the width of the cell, it is considered an invalid sign transition. The original geometry is then ray intersected to determine inside/outside and the result used to determine which sign is correct. The correct sign is then propagated forward through the model.

Max Sign Sweep Count

The sign sweeps are repeated until no signs are flipped (ie, all transitions are within the threshold) or this maximum is reached. Too low of a sign sweep threshold may prevent the process from converging. Otherwise, it tends to converge very quickly.

Drag

Normal Drag

The component of drag in the directions normal to the surface. Increasing this will make the object go along with any wind that blows against it. For realistic wind interaction, the Normal Drag should be chosen larger (about 10 times larger) than the tangent drag.

Tangent Drag

The component of drag in the direction tangent to the surface. Increasing this will make the object go along with any wind that blows tangent to the object.

External Velocity Field

The name of the external velocity fields on affectors that the object will respond to. The default is `vel`, which will make the object react to fluids and smoke when the Tangent Drag and the Normal Drag have been chosen sufficiently large. The Tangent Drag and Normal Drag forces are computed by comparing the object’s velocity with the external velocity.

External Velocity Offset

This offset is added to any velocity that’s read from the velocity field. When there’s no velocity field, then the offset can be used to create a wind force which has constant velocity everywhere. This wind effect is more realistic and more accurate than the wind that is generated by DOP Forces.

Creation

Creation Frame Specifies Simulation Frame

Determines if the creation frame refers to global Houdini frames (`\$F`) or to simulation specific frames (`\$SF`). The latter is affected by the offset time and scale time at the DOP network level.

Creation Frame

The frame number on which the object will be created. The object is created only when the current frame number is equal to this parameter value. This means the DOP Network must evaluate a timestep at the specified frame, or the object will not be created.

For example, if this value is set to 3.5, the Timestep parameter of the DOP Network must be changed to `1/(2*\$FPS)` to ensure the DOP Network has a timestep at frame 3.5.

Number of Objects

Instead of making a single object, you can create a number of identical objects. You can set each object’s parameters individually by using the `\$OBJID` expression.

Object Name

The name for the created object. This is the name that shows up in the details view and is used to reference this particular object externally.

Solve On Creation Frame

For the newly created objects, this parameter controls whether or not the solver for that object should solve for the object on the timestep in which it was created.

Usually this parameter will be turned on if this node is creating objects in the middle of a simulation rather than creating objects for the initial state of the simulation.

Allow Caching

By preventing a large object from being cached, you can ensure there is enough room in the cache for the previous frames of its collision geometry.

This option should only be set when you are working with a very large sim. It is much better just to use a larger memory cache if possible.

Initial State

Controls on this tab allow you to set the initial states of the object’s position, pivot, rotation, initial velocity, and angular velocity.

Attributes

The finite element solver will recognize and use attributes on the simulated geometry. In the DOP network, this simulation geometry is attached to the simulated object as a sim-data with name `Geometry`. When an object is created, then the geometry and all the corresponding attributes are read from the Initial Geometry. This includes the standard position and velocity point attributes `P` and `v`.

The finite element solve supports input attributes and output attributes. Some attributes, such as the simulation state, are both input and output attributes. The input attributes include multiplier attributes for material properties, fracture attributes, and attributes for controlling target positions and corresponding hard/soft constraints. The output attributes include optional attributes for tet quality, energy densities, FEM node forces, collision info attributes and fracture info attributes.

Material Property Multiplier Attributes

Each of the material properties of a simulated object can be locally modified using multiplier point attributes. As a rule, each of the material properties in the Model tab of an object can be affected by a multiplier attribute. As a rule, the name of the parameter is the name of the attribute. The name of the attribute is the name that is displayed after "Parameter:" when you hover over a parameter with your mouse cursor.

You can locally change the material properties of the object using point attributes. For example, you can make some polygons resists stretching and bending more than other polygons. These attributes work as multipliers for the parameters in the Model tab: The stiffness multiplier is a convenient way to modify the local stiffness for all object types that are recognized by the finite element solver:

Name Class Type Description
`stiffness` Point Float Multiplier for all types of stiffnesses.
`dampingratio` Point Float Multiplier for all damping ratios.
`massdensity` Point Float Multiplier for all mass densities.

For solid objects, the following multiplier point attributes can be used to modify the local behavior:

Name Class Type Description
`solidstiffness` Point Float Multiplier for both the shape stiffness and the volume stiffness of a Solid Object.
`solidshapestiffness` Point Float Multiplier for the shape stiffness of a Solid Object.
`solidvolumestiffness` Point Float Multiplier for the volume stiffness of a Solid Object.
`solidmassdensity` Point Float Multiplier for the mass density of a Solid Object.

Collision Control Attributes

The FEM solver looks at collision identifiers to decide which primitive pairs are allowed to collide. The rule is that a pair of primitives may collide if they have the same collision identifier. (This mechanism may possibly be extended in a future release, allowing the user to specify exactly which collision identifier pairs may collide.) Collisions can be suppressed altogether for certain primitives by setting the special value -1. A collision id may be specified separately for the interior and the exterior side of each polygon and tetrahedron. The exterior side of a polygon is decided using the winding order convention, just like the normal direction. If interiorcollisionid is not specified, then the default collision id of 0 is used for triangles, but interior collisions are disabled for tets. If exteriorcollisionid is not specified, then the default collision id of 0 is used for both tets and triangles.

Consider, as an example, an FEM muscle simulation, we may want the muscles to collide only with the interior side of the skin polygons, so the exteriorcollisionid for those polygons may be set to -1 (disable).

Name Class Type Description
`exteriorcollisionid` Primitive Integer Collision identifier for the exterior side of a polygon or tet surface
`interiorcollisionid` Primitive Integer Collision identifier for the interior side of a polygon or tet surface

Material Space Attributes

The attribute `materialP` can be thought of as the positions of the simulated object in the material space. `materialP` is the undeformed configuration relative to which the current position `P` determines the deformation of a simulated object. `materialP` must stay the same throughout the entire simulation. The finite element solver relies on assumption that the `materialP` attribute remains unchanged from frame to frame; it should never be modified externally (e.g., through a SOP solver) otherwise bad simulation results will be produced.

In the case where no Rest Shape is specified and nor `restP` attribute is provided, `materialP` can be thought of as a permanent rest position. If no animation of the rest position is required in a sim, only `materialP` should be specified (no `restP`). At any stage in the simulation, it is the mapping from `materialP` to the current `P` that determines the deformation of tets in simulated objects. The deformation in turn defines the energy stored inside the object.

To help determine the anisotropic behavior of solids, including fiber contraction, the solver can makes use of local UVW frames. These UVW frames may be specified directly using the vertex/point attributes `materialU`, `materialV`, and `materialW`. Alternatively, they may be inferred from UVW positions that may be specified by a vertex/point position attribute `materialuvw`. The FEM solver embeds the UVW directions within the material space that may be specified by the attribute `materialP`. To get the correct idea of how this works, UVW directions that are fed into the FEM solver should be visualized relative to the material position `materialP`.

For FEM muscle simulations, the easiest way to specify the muscle fiber direction is through vertex/point attribute `materialW`. It is fine if no `materialU` and `materialV` directions are specified in this case, as the solver will infer arbitrary `materialU` and `materialV` directions from `materialW` in that case.

The attribute `materialuvw` can be used to specify a UVW parametrization of the material space. The U, V and W directions that are implied by `materialuvw` matter if the anisotropic controls are used or when the fiber controls are used on a simulated object. For the FEM muscle simulation use case, the fiber controls are an important tool for controlling muscle contraction.

Similar to `materialuvw`, the `materialuv` attribute can be used to specify UV directions for cloth. This attribute is essential for triangle meshes, in particular, to define the warped and weft directions for cloth.

Name Class Type Description
`materialP` Point or Vertex Vector Material position of each point, defining the material space
`materialU` Point or Vertex Vector The U direction within the material space
`materialV` Point or Vertex Vector The V direction within the material space
`materialW` Point or Vertex Vector The W direction within the material space
`materialuvw` Point or Vertex Vector Local material uvw coordinates for each point or vertex of a tet.
`materialuv` Point or Vertex Vector Local material uvw coordinates for each point or vertex of a polygon or polysoup.

Material Property Multiplier Attributes

 `fracturepart` Primitive Integer Partitions the object into unbreakable parts. Must be either -1 (no part) or a nonnegative number that indicates a part. `enablefracturing` Point/Vertex Integer Locally enable/disable fracturing for points or vertices. `fracturethreshold` Point/Vertex Float Multiplier for the object’s Fracture Threshold.

Fracturing Control Attributes

When you create a simulation with fracturing, it is recommended to specify chunks of tetrahedrons that you want to stay together. Otherwise, the fracturing process may create a very large amount of separate pieces, many of which may consist of single tetrahedrons. For this purpose, you can assign a nonnegative integer to each chunk using the `fracturepart` attribute. In areas where you don’t want to specify parts, you can set `fracturepart` to -1, which means that each primitive in that region will become its own part. Real-life materials tend not to be equally strong everywhere. For realistic results, it is recommended to vary the Fracture Threshold locally using the vertex attribute `fracturethreshold`.

 `fracturepart` Primitive Integer Partitions the object into unbreakable parts. Must be either -1 (no part) or a nonnegative number that indicates a part. `enablefracturing` Point/Vertex Integer Locally enable/disable fracturing for points or vertices. `fracturethreshold` Point/Vertex Float Multiplier for the object’s Fracture Threshold.

Drag Force Control Attributes

The behavior of the drag force can be modified locally using the following attributes:

 `normaldrag` Primitive Float Multiplier for the object’s Normal Drag. `tangentdrag` Primitive Float Multiplier for the object’s Tangent Drag.

Reference Attributes

The attribute `baseP` can be used to specify a generic base position for all the object points. This attribute’s values must not be changed during a simulation. When the user does not specify `baseP`, the solver creates this point attribute based on the point positions on the creation frame. This attribute is used as a fallback; whenever the user does not specify `materialP`, the attribute `baseP` is read instead. In the same way, `baseP` is used as a fallback for when no `restP` or `targetP` attributes are provided. Finally, `baseP` is used to bind the simulated and the embedded geometry, in the embedded workflow (e.g., a T-pose). This embedded binding looks at the `baseP` position attribute on both the simulated geometry and the embedded geometry. If no `baseP` attribute is provided by the user on the embedded geometry, the solver creates the `baseP` attribute on the embedded geometry based on the position `P` at the creation frame.

The attribute `restP` can be used to specify an animated rest position for all the object points. For example, at each frame `restP` may be modified in a SOP Solver before the finite element solver. Among other things this makes it possible to create plastic deformation kinds of effects. When the rest should stay the same during an entire simulation the attribute `restP` should not be used. In that case, it is sufficient to specify only an attribute `materialP`, which would act as a permanent, unchanged rest position. If no attribute `materialP` is specified, the solver falls back to the `baseP` attribute that gets automatically created at the creation frame. table>>

The attribute `initialpid` stores the initial point index for each point. This is the point index at the creation time of the object. This attribute is created only when fracturing is enabled on both the object and the solver. The finite element solver uses this attribute for the options Import Rest Geometry and Import Target Geometry to transfer animated positions and velocities in SOPs to the current fractured topology in the simulated object.

Name Class Type Description
`initialpid` Point Integer Initial point index for each point.

Target Attributes

Target attributes can be used to make a simulated object partially follow a target animation. The attribute `targetP` can be used to specify a target position for each object point. When you use the Import Target Geometry option on the simulated object, the `targetP` will be set automatically every frame. Alternatively, you can create and modify these attributes yourself, using a Multi Solver and a SOP Solver. The target positions and velocities allow the user to mix animation and simulation in a very stable way (assuming the Target Strength and Target Damping parameters have been set on the object). You can set the Target Strength and Target Damping parameters on the object to express how strongly the object should match the target position and velocity, respectively. This is a way to create soft constraints. You can use the `pintoanimation` to create hard constraints that make the simulated points follow `targetP` exactly.

Name Class Type Description
`targetP` Point or Vertex Vector Target position of each point.
`targetstrength` Point Float Multiplier for the object’s Target Strength. If this attribute is missing, a multiplier of 1 is used at all points.
`targetdamping` Point Float Multiplier for the object’s Target Damping. If this attribute is missing, a multiplier of 1 is used at all points.
`pintoanimation` Point Int When 1, the point is hard constrained to the target animation (e.g., `targetP`). When zero, the point is unconstrained.

Fiber Attributes

The `fiberscale` point attribute acts as a multiplier for the rest strain in the fiber direction. The fiber direction itself can be specified using the `materialW` vertex/point attribute. Among other things, this is useful for FEM muscle simulations. If the `fiberscale` is changed from 1 to 0.5, then the muscle wants to be half as long as before in the direction of the fiber. If you animate the `fiberscale` in a SOP Solver such that it decreases from 1 to a smaller value, you will cause a muscle contraction in the sim.

The `fiberstiffness` point attribute acts as a multiplier for the stiffness along the fiber direction. The fiber direction of the material is determined by the W axis of the `materialuvw` coordinates. `fiberstiffness` works as a multiplier on top of all the other material property multipliers, including the anisotropic multipliers. If the `fiberstiffness` changed from 1 to 10, then the stiffness along the fiber direction becomes 10 stronger than before. This can be used to control how strong and how quick the effect of muscle flexing using the `fiberscale` attribute takes effect.

For `fiberscale`/`fiberstiffness` to have the desired effect, it is important that UVW directions are specified. A material-space UVWs for FEM muscles can be specified using the `materialuvw` point/vertex attribute. By providing `materialuvw` as a vertex attribute, you are able to provide a local UVW space for each individual tet, which gives you to option of providing a separate UVW frame to each tet.

Name Class Type Description
`fiberstiffness` Point Float Multiplier for stiffness along the fiber direction, the W direction implied by `materialuvw`.
`fiberscale` Point Float Multiplier for the rest strain along the fiber direction, the W direction implied by `materialuvw`.

State Attributes

Below is a list of attributes that are maintained internally by the solver. Each of these attributes is written to at the end of each solve and read from at the start of the next solve. You should not modify any of these attributes yourself. When you do, the solver is likely to become unstable and you will get bad results. However, you can inspect the values in these attributes in your network for visualization or for the creation of secondary effects.

At each frame, the finite element solver computes a new physical state for each simulated object. The physical state of the object is represented by the point attributes `P` and `v`, representing the position and velocity, respectively. The solver’s integration scheme maintains additional attributes `a` for acceleration and `j` for jerk.

The point attributes `P`, `v`, `a`, and `j` store the current integration state of the object. These attributes should not be modified during the simulation because the finite element solver will become unstable and produce low-quality results.

Name Class Type Description
`P` Point Vector Do not modify! Current position of each object point.
`v` Point Vector Do not modify! Current velocity of each object point.
`accel` Point Vector Do not modify! Current acceleration of each object point.
`jerk` Point Vector Do not modify! Current jerk of each object point.

Embedded Geometry Attributes

These attributes are created on the Embedded Geometry of the Solid Object. The `parent` attribute is maintained by the embedding code itself, and should not be modified. The `baseP` point attribute can be provided on the Embedded Geometry by the user to control the binding between the simulated geometry and the embedded geometry. If no `baseP` is provided, it will be copied from the point positions stored in `P` at the creation frame. The alignment happens relative to the `baseP` point attribute on the simulated geometry. If the simulated geometry has a `materialP` vertex or point attribute, then this attribute takes precedence, allowing control per vertex, rather than per point, if necessary. When you want to ensure that embedded geometry ends up on the desired side of a fracture between simulated geometry, you can use the combination of vertex attributes `baseP` on the embedded geometry and `restP` on the simulated geometry. This allows you to line up the embedded geometry with the separate parts in the simulated geometry, for example using the Exploded View SOP. The `fracturepart` attribute allows you to make sure that the embedded geometry follows the right parts when it gets fractured. When both the simulated and the embedded geometry have the `fracturepart` attribute, the finite element solver will parent embedded geometry to simulated geometry that has the same fracture part.

Name Class Type Description
`parent` Primitive Float The index of a parent primitive in the simulated geometry.
`baseP` Point Float Base positions used for alignment with simulated mesh.
`fracturepart` Point or Vertex Float Optional user-specified fracture part ID.
`P` Point Float Positions that correspond to the deformed state.
`v` Point Float Velocities that correspond to the deformed state.
`N` Point or Vertex Float Normals that correspond to the deformed state.

Optional Output Attributes

These are attributes that are optionally generated by the solver, when the generation is enabled on the simulated object. These attributes can be useful for visualization, for example, using the Finite Element Visualization SOP. Additionally, these attributes may be used to create secondary effects, for example, particles flying off in regions where fracturing occurs. The optional output attributes are also expected by the Finite Element Visualization SOP.

The following attribute is generated when Create Quality Attributes is turned on:

Name Class Type Description
`quality` Primitive Float A quality metric between 0 (worst) and 1 (best)

Finite element simulation tends to be sensitive to the quality of the incoming primitives. Low quality primitives may slow down, destabilize or lock a finite element simulation. Low quality primitives are best avoided by using the Solid Embed as a tool to create your tet mesh. Although various quality metrics exist for tetrahedra, the one that’s generated by the solver in this attribute is the one that best matches Houdini’s finite element solution.

The solver generates energy-density attributes for each object that has Create Energy Attributes turned on. The material property settings in the Model tab and the corresponding multiplier attributes result in potential energy, energy dissipation and kinetic energy. For each of these three contributions, local densities are computed within the solver. These densities and quantities derived from them are used to determine the motion and behavior of the objects that are solved by the finite element solver.

Name Class Type Description
`potentialdensity` Point Float The local density of deformation energy
`dissipationdensity` Point Float The local density of the rate of energy loss
`kineticdensity` Point Float The local density of the kinetic energy

The `potentialdensity` attribute is directly affected by the stiffness parameters in the Model tab. The `kineticdensity` is proportional to the mass density that is specified for the object. The `dissipationdensity` is related to the damping settings.

If Create Fracture Attributes is enabled on the simulated object, then the `fracturecount` point attribute is created. The point attribute `fracturecount` maintains for each point, the number of times that the point has been involved in a fracture. So any point with a nonzero value of `fracturecount` has been involved fracturing.

Name Class Type Description
`fracturecount` Point Integer The number of times a point was fractured during the simulation

Legacy Attributes

In most situations where you want to influence a finite-element simulation, you will want to use soft constraints to achieve this, for example, target constraints, region constraints, or the target strength/damping settings on the object. These are first-class solver features that work in a stable way with the solver and should produce high quality results when used correctly. Purely for backwards compatibility, a force force attribute is still supported. Because the force force attribute lacks essential information that the solver needs, this attribute cannot be relied on when stability and quality are important. When setting up a new sim, alternatives such as soft targeting, region constraints and animated rest positions should be considered instead of the force force attribute.

Name Class Type Description
`fexternal` Force Vector External force density
`force` Force Vector Another name for external force density

Locals

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.

Dynamics nodes

• Marks a simulation object as active or passive.

• Creates affector relationships between groups of objects.

• Blends between a set of animation clips based on the agent’s turn rate.

• Layers additional animation clips onto an agent.

• Defines a target that an agent can turn its head to look at.

• Chooses an object/position for the head of an agent to look at.

• Moves the head of an agent to look at a target.

• Moves the head of an agent to look at a target.

• Adapts the legs of an agent to conform to terrain and prevent the feet from sliding.

• Project the agent/particle points onto the terrain

• Defines an orientation that aligns an axis in object space with a second axis defined by the relative locations of two positional anchors.

• Defines multiple points, specified by their number or group, on the given geometry of a simulation object.

• Defines orientations based on multiple points on the given geometry of a simulation object.

• Defines a position by looking at the position of a point on the geometry of a simulation object.

• Defines an orientation by looking at a point on the geometry of a simulation object.

• Defines a position by looking at the position of a point on the geometry of a simulation object.

• Defines an orientation by looking at a point on the geometry of a simulation object.

• Defines a position by looking at the position of a particular UV coordinate location on a primitive.

• Defines a position by specifying a position in the space of some simulation object.

• Defines an orientation by specifying a rotation in the space of some simulation object.

• Defines multiple attachment points on a polygonal surface of an object.

• Defines a position by specifying a position in world space.

• Defines an orientation by specifying a rotation in world space.

• Attaches data to simulation objects or other data.

• Creates relationships between simulation objects.

• Attaches the appropriate data for Bullet Objects to an object.

• Sets and configures an Bullet Dynamics solver.

• Applies a uniform force to objects submerged in a fluid.

• Attaches the appropriate data for Cloth Objects to an object.

• Defines the mass properties.

• Defines the physical material for a deformable surface.

• Defines the internal cloth forces.

• Creates a Cloth Object from SOP Geometry.

• Defines the plasticity properties.

• Constrains part of the boundary of a cloth object to the boundary of another cloth object.

• Defines how cloth uses target.

• Defines a way of resolving collisions involving a cloth object and DOPs objects with volumetric representations (RBD Objects, ground planes, etc.)

• Constrains an object to remain a certain distance from the constraint, and limits the object’s rotation.

• Constrains pairs of RBD objects together according to a polygon network.

• Defines a set of constraints based on geometry.

• Visualizes the constraints defined by constraint network geometry.

• Creates multiple copies of the input data.

• Sets and configures a Copy Data Solver.

• Mimics the information set by the Copy Object DOP.

• Defines a Crowd Fuzzy Logic

• Creates a crowd object with required agent attributes to be used in the crowd simulation.

• Updates agents according to their steer forces and animation clips.

• Defines a Crowd State

• Defines a transition between crowd states.

• Defines a Crowd Trigger

• Combines multiple crowd triggers to build a more complex trigger.

• Adds a data only once to an object, regardless of number of wires.

• Deletes both objects and data according to patterns.

• Applies force and torque to objects that resists their current direction of motion.

• Defines how the surrounding medium affects a soft body object.

• Dynamics nodes set up the conditions and rules for dynamics simulations.

• Controls Embedded Geometry that can be deformed along with the simulated geometry in a finite element simulation.

• Creates an Empty Data for holding custom information.

• Creates an Empty Object.

• Constrains points of a solid object or a hybrid object to points of another DOP object.

• Creates an FEM Hybrid Object from SOP Geometry.

• Constrains regions of a solid object or a hybrid object to another solid or hybrid object.

• Creates a simulated FEM solid from geometry.

• Constrains a set of points on a cloth object to the surface of a Static Object.

• Constrains an FEM object to a target trajectory using a hard constraint or soft constraint.

• Attaches the appropriate data for Particle Fluid Objects to become a FLIP based fluid.

• Evolves an object as a FLIP fluid object.

• Applies forces on the objects as if a cone-shaped fan were acting on them.

• Fetches a piece of data from a simulation object.

• Applies forces to an object using some piece of geometry as a vector field.

• Creates a vortex filament object from SOP Geometry.

• Evolves vortex filament geometry over time.

• Imports vortex filaments from a SOP network.

• Saves and loads simulation objects to external files.

• Allows a finite-element object to generate optional output attributes.

• Attaches the appropriate data for Fluid Objects to an object.

• Applies forces to resist the current motion of soft body objects relative to a fluid.

• Attaches the appropriate data for Fluid Objects to an object.

• A solver for Sign Distance Field (SDF) liquid simulations.

• A microsolver that adjusts an internal coordinate system attached to fluid particles in a particle fluid simulation.

• A microsolver that advects fields and geometry by a velocity field.

• A microsolver that advects fields and geometry by a velocity field using OpenCL acceleration.

• A microsolver that advects fields by a velocity field.

• A microsolver that computes analytic property of fields.

• A microsolver that swaps geometry attributes.

• A microsolver that blends the density of two fields.

• A microsolver that blurs fields.

• A microsolver that determines the collision field between the fluid field and any affector objects.

• A microsolver that builds a mask out of positive areas of the source fields.

• A microsolver that builds a mask for each voxel to show the presence or absence of relationships between objects.

• A microsolver that calculates an adhoc buoyancy force and updates a velocity field.

• A microsolver that performs general calculations on a pair of fields.

• A microsolver that detects collisions between particles and geometry.

• A microsolver that applies a combustion model to the simulation.

• A microsolver that adjusts an SDF according to surface markers.

• A microsolver that computes the cross product of two vector fields.

• A DOP node that creates forces generated from a curve.

• A microsolver that scales down velocity, damping motion.

• A microsolver that diffuses a field or point attribute.

• A microsolver that dissipates a field.

• Adds fine detail to a smoke simulation by applying "disturbance" forces to a velocity field.

• A microsolver that runs once for each matching data.

• A microsolver that embeds one fluid inside another.

• A microsolver that enforces boundary conditions on a field.

• A microsolver that equalizes the density of two fields.

• A microsolver that equalizes the volume of two fields.

• A microsolver that emits a DOP error.

• A microsolver that evaluates the external DOPs forces for each point in a velocity field and updates the velocity field accordingly.

• A microsolver that extrapolates a field’s value along an SDF.

• A microsolver that creates a feathered mask out of a field.

• A microsolver that calculates and applies feedback forces to collision geometry.

• A data node that fetches the fields needed to embed one fluid in another.

• Runs CVEX on a set of fields.

• Runs CVEX on a set of fields.

• A microsolver that copies the values of a field into a point attribute on geometry.

• Filters spurious divergent modes that may survive pressure projection on a center-sampled velocity field.

• A microsolver that defragments geometry.

• A microsolver that creates a signed distance field out of geometry.

• A micro solver that transfers meta data on simulation objects to and from geometry attributes.

• Blends a set of SOP volumes into a set of new collision fields for the creation of a guided simulation.

• A microsolver that copies Impact data onto point attributes.

• A microsolver that applies forces to a particle fluid system.

• A microsolver that solves its subsolvers at a regular interval.

• A microsolver that clamps a field within certain values.

• A microsolver that keeps particles within a box.

• A microsolver that combines multiple fields or attributes together.

• A microsolver that adaptively sharpens a field.

• A microsolver that looksup field values according to a position field.

• A microsolver that rebuilds fields to match in size and resolution to a reference field.

• A microsolver that arbitrary simulation data between multiple machines.

• A microsolver that exchanges boundary data between multiple machines.

• A microsolver that exchanges boundary data between multiple machines.

• A microsolver that balances slices data between multiple machines.

• A microsolver that exchanges boundary data between multiple machines.

• Executes the provided kernel with the given parameters.

• A microsolver that counts the number of particles in each voxel of a field.

• A microsolver that computes pairwise collision forces between particles that represent instanced spheres.

• A microsolver that moves particles to lie along a certain isosurface of an SDF.

• A microsolver that separates adjacent particles by adjusting their point positions..

• A microsolver that copies a particle system’s point attribute into a field.

• A microsolver that converts a particle system into a signed distance field.

• A microsolver that removes the divergent components of a velocity field.

• A microsolver that removes the divergent components of a velocity field using an adaptive background grid to increase performance.

• A microsolver that removes the divergent components of a velocity field using a multi-grid method.

• A microsolver that removes the divergent components of a velocity field.

• A microsolver that reduces a field to a single constant field .

• A microsolver that reduces surrounding voxels to a single value.

• A microsolver that reinitializes a signed distance field while preserving the zero isocontour.

• A microsolver that repeatedly solves its input.

• A microsolver that changes the size of fields.

• A microsolver that resizes a fluid to match simulating fluid bounds

• A microsolver that initializes a rest field.

• A microsolver that converts an SDF field to a Fog field.

• A microsolver that computes the forces to treat the fluid simulation as sand rather than fluid.

• A microsolver that seeds marker particles around the boundary of a surface.

• A microsolver that seeds particles uniformly inside a surface.

• Applies a Shredding Force to the velocity field specified.

• A microsolver that computes slice numbers into an index field.

• Adjusts a fluid velocity field to match collision velocities.

• A microsolver that calculates the forces imparted by a strain field.

• A microsolver that updates the strain field according to the current velocity field.

• A microsolver that substeps input microsolvers.

• A microsolver that snaps a surface onto a collision surface.

• A microsolver that calculates a surface tension force proportional to the curvature of the surface field.

• A microsolver that synchronizes transforms of simulation fields.

• A microsolver that applies a force towards a target object.

• Modifies the temperature of a FLIP over time.

• Applies Turbulence to the specified velocity field.

• Up-scales and/or modifies a smoke, fire, or liquid simulations.

• A microsolver that reorients geometry according to motion of a velocity field.

• A microsolver that applies viscosity to a velocity field.

• A microsolver that seeds flip particles into a new volume region.

• Remaps a field according to a ramp.

• Applies a confinement force on specific bands of sampled energy.

• Applies a vortex confinement force to a velocity field.

• Applies a confinement force on specific bands of sampled energy.

• A microsolver that applies forces to a velocity field or geometry according to vorticle geometry.

• A DOP node that adds the appropriately formatted data to represent vorticles.

• A DOP node that recycles vorticles by moving them to the opposite side of the fluid box when they leave.

• A microsolver that performs a wavelet decomposition of a field.

• A microsolver that applies a wind force.

• Runs CVEX on geometry attributes.

• Runs a VEX snippet to modify attribute values.

• Applies a gravity-like force to objects.

• Creates a ground plane suitable for RBD or cloth simulations.

• Creates simulation object groups.

• Defines a constraint relationship that must always be satisfied.

• Attaches the appropriate data for Hybrid Objects to an object.

• Stores filtered information about impacts on an RBD object.

• Applies an impulse to an object.

• Creates an index field.

• Visualizes an index field.

• Creates DOP Objects according to instance attributes

• Marks a simulation object as intangible or tangible.

• Stores the name of the scene level object source for this DOP object.

• Apply forces on objects using a force field defined by metaballs.

• Creates a matrix field.

• Visualizes a matrix field.

• Merges multiple streams of objects or data into a single stream.

• Modifies or creates options on arbitrary data.

• Defines an object’s position, orientation, linear velocity, and angular velocity.

• Unified visualization of multiple fields.

• A DOP that transfers arbitrary simulation data between multiple machines.

• Does nothing.

• Creates position information from an object’s transform.

• Serves as the end-point of the simulation network. Has controls for writing out sim files.

• Uses vortex filaments to move particles.

• A POP node that uses velocity volumes to move particles.

• A POP node that attracts particles to positions and geometry.

• A POP node that copies volume values into a particle attribute.

• A POP node that resets the stopped attribute on particles, waking them up.

• A POP node that applies a force around an axis.

• A POP node that reacts to collisions.

• A POP node that detects and reacts to collisions.

• A POP node marks particles to ignore implicit collisions.

• A POP node that colors particles.

• A POP node that creates forces generated from a curve.

• A POP node that applies drag to particles.

• A POP node that applies drag to the spin of particles.

• A POP node that applies a conical fan wind to particles.

• A POP node that creates a simple fireworks system.

• A POP node that floats particles on the surface of a liquid simulation.

• A POP node that applies a flocking algorithm to particles.

• Controls local density by applying forces between nearby particles.

• A POP node that applies forces to particles.

• A POP node that applies sand grain interaction to particles.

• A POP node that groups particles.

• A POP node that sets up the instancepath for particles.

• A POP node that applies forces between particles.

• A POP node that kills particles.

• A POP node that limits particles.

• A POP node that applies forces within the particle’s frame.

• A POP solver that generates particles at a point.

• A POP node makes a particle look at a point.

• A POP node that applies forces according to metaballs.

• Converts a regular particle system into a dynamic object capable of interacting correctly with other objects in the DOP environment.

• A POP node that sets various common attributes on particles.

• A POP node that sets attributes based on nearby particles.

• A POP Node that generates particles from incoming particles.

• A POP node that creates a spongy boundary.

• A POP solver updates particles according to their velocities and forces.

• A POP node that generates particles from geometry.

• A POP node that sets the speed limits for particles.

• A POP node that sets the spin of particles..

• A POP node that uses the vorticity of velocity volumes to spin particles.

• A POP node that sets the sprite display for particles.

• Applies force to agents/particles to align them with neighbors.

• Applies anticipatory avoidance force to agents/particles to avoid potential future collisions with other agents/particles.

• Applies forces to agents/particles to bring them closer to their neighbors.

• Applies forces to agents/particles calulated using a VOP network.

• Applies force to agents/particles to avoid potential collisions with static objects.

• Applies force to agents/particles according to directions from a path curve.

• Applies force to agents/particles to move them toward a target position.

• Apply force to agents/particles to move them apart from each other.

• Used internally in the crowd solver to integrate steering forces.

• Constrains agent velocity to only go in a direction within a certain angle range of its current heading, to prevent agents from floating backward.

• Apply forces to agents/particles to create a random motion.

• A POP node that creates a new stream of particles.

• A POP node that applies torque to particles, causing them to spin.

• Runs CVEX on a particle system.

• A POP node that directly changes the velocity of particles.

• A POP node that applies wind to particles.

• Runs a VEX snippet to modify particles.

• Emits particles into a particle fluid simulation.

• Removes fluid particles that flow inside of a specified boundary from a simulation.

• Visualizes particles.

• Creates simulation object groups based on an expression.

• Defines the base physical parameters of DOP objects.

• Applies a force to an object from a particular location in space.

• Creates position information from a point on some SOP geometry.

• Associates a position and orientation to an object.

• Sets and configures a Pyro solver. This solver can be used to create both fire and smoke.

• Performs a sparse pyro simulation on the given object. This solver can be used to create both fire and smoke.

• Constrains an RBD object to a certain orientation.

• Constrains an RBD object to have a certain orientation, but with a set amount of springiness.

• Automatically freezes RBD Objects that have come to rest

• Attaches the appropriate data for RBD Objects to an object.

• Creates a number of RBD Objects from SOP Geometry. These individual RBD Objects are created from the geometry name attributes.

• Constrains an object to two constraints, creating a rotation similar to a hinge or a trapeze bar.

• Creates an RBD Object from SOP Geometry.

• Creates a single DOP object from SOP Geometry that represents a number of RBD Objects.

• Constrains an RBD object a certain distance from the constraint.

• Creates a simulation object at each point of some source geometry, similarly to how the Copy surface node copies geometry onto points.

• Sets and configures a Rigid Body Dynamics solver.

• Constrains an object to remain a certain distance from the constraint, with a set amount of springiness.

• Alters the state information for an RBD Object.

• Saves the state of a DOP network simulation into files.

• Applies forces to an object according to the difference between two reference frames.

• Sets and configures a Rigid Body Dynamics solver.

• Attaches the appropriate data for Ripple Objects to an object.

• Creates an object from existing geometry that will be deformed with the ripple solver.

• Animates wave propagation across Ripple Objects.

• Creates a signed distance field representation of a piece of geometry that can be used for collision detection.

• A microsolver that performs general calculations on a pair consisting of a DOP field and a SOP volume/VDB.

• Creates a scalar field from a SOP Volume.

• Creates a vector field from a SOP Volume Primitive.

• Creates a scalar field.

• Visualizes a scalar field.

• Defines the internal seam angle.

• Defines the mass density of a Cloth Object.

• Divides a particle system uniformly into multiple slices along a line.

• Specifies a cutting plane to divide a particle system into two slices for distributed simulations.

• Constrains an object to rotate and translate on a single axis, and limits the rotation and translation on that axis.

• Attaches the appropriate data for Smoke Objects to an object.

• Creates an Smoke Object from SOP Geometry.

• Creates an empty smoke object for a pyro simulation.

• Sets and configures a Smoke solver. This is a slightly lower-level solver that is the basis for the Pyro solver.

• Performs a sparse smoke simulation on the given object. This is a slightly lower-level solver that is the basis for the sparse pyro solver.

• Constrains a set of points on a soft body object to a certain position using a hard constraint or soft constraint.

• Constrains a point on a soft body object to a certain position.

• Constrains a point on a soft body to a certain position, with a set amount of springiness.

• Defines how a soft body object responds to collisions.

• Defines how a Soft Body Object responds to collisions.

• Defines how a Soft Body Object responds to collisions.

• Defines how a Soft Body Object responds to collisions.

• Allows the user to import the rest state from a SOP node.

• Sets and configures a Soft Body solver.

• Defines the strengths of the soft constraint on a soft body object.

• Controls the anisotropic behavior of a Solid Object.

• Attaches the appropriate data for Solid Objects to an object.

• Defines the mass density of a Solid Object.

• Defines how a Solid Object reacts to strain and change of volume.

• This builds a tree of spheres producing bounding information for an edge cloud.

• This builds a tree of spheres producing bounding information for a point cloud.

• Splits an incoming object stream into as many as four output streams.

• Creates a Static Object from SOP Geometry.

• Allows you to inspect the behavior of a static object in the viewport.

• Control the thickness of the object that collides with cloth.

• Passes one of the input object or data streams to the output.

• Creates a Terrain Object from SOP Geometry.

• Defines a way of resolving collisions between two rigid bodies.

• Applies a uniform force and torque to objects.

• Applies forces on the objects according to a VOP network.

• Creates a vector field.

• Visualizes a vector field.

• Modifies common Vellum Constraint properties during a Vellum solve.

• Microsolver to create Vellum constraints during a simulation.

• Creates a DOP Object for use with the Vellum Solver.

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

• Sets and configures a Vellum solver.

• A Vellum node that creates Vellum patches.

• Applies an impulse to an object.

• A microsolver to create soft references to visualizers on itself.

• Imports SOP source geometry into smoke, pyro, and FLIP simulations.

• Defines a way of resolving collisions involving two rigid bodies with volume.

• Attaches the appropriate data to make an object fractureable by the Voronoi Fracture Solver

• Defines the parameters for dynamic fracturing using the Voronoi Fracture Solver

• Dynamically fractures objects based on data from the Voronoi Fracture Configure Object DOP

• Applies a vortex-like force on objects, causing them to orbit about an axis along a circular path.

• Creates a Whitewater Object that holds data for a whitewater simulation.

• Sets and configures a Whitewater Solver.

• Applies forces to resist the current motion of objects relative to a turbulent wind.

• Constrains a wire point’s orientation to a certain direction.

• Constrains a wire point’s orientation to a certain direction, with a set amount of springiness.

• Attaches the appropriate data for Wire Objects to an object.

• Defines the elasticity of a wire object.

• Constraints a wire point to a certain position and direction.

• Creates a Wire Object from SOP Geometry.

• Defines the physical parameters of a wire object.

• Defines the plasticity of a wire object.

• Sets and configures a Wire solver.

• Defines a way of resolving collisions involving a wire object and DOPs objects with volumetric representations.

• Defines a way of resolving collisions between two wires.