Gas OpenCL Enforce Boundary dynamics node

Uses OpenCL to perform boundary enforcement for fluid fields.

On this page	Parameters Locals
Since	19.5

The Gas OpenCL Enforce Boundary DOP takes care of boundary enforcement for fluid fields, using collider’s surface and velocity VDBs. In particular, this node overwrites Velocity Field values inside the collider to match its velocity; additionally, any listed Field will be reset inside the collider.

Note

If the object has an attached position data, this DOP will respect its translation.

Parameters ¶

Collider Type

Controls the mode of operation for this DOP.

Individual Volumes

In this mode, the collider is represented by the current Surface VDB and Velocity VDB in the Collider Geometry. If Instance Geometry is enabled, the same collider is instanced at its points.

Packed Sets

This mode treats Collider Geometry as a library of colliders, each element being a named packed primitive containing its signed distance field. Each point in Instance Geometry intances a particular collider, identified by the name. Velocity VDB is not exposed, as every piece is assumed to be rigid.

You can use the Pyro Source Pack SOP to generate a library of colliders from rigid body pieces, by setting its Input parameter to Rigid Body Pieces.

Field

List of fields to enforce boundary on: voxels that fall inside a collider will be set to 0.

Velocity Field

Name of the velocity vector field. Velocity values inside the collider will be changed to reflect the collider’s motion. The collider’s velocity is read from Velocity VDB (or assumed to be 0 if not available). if Instance Geometry is being used, linear and angular velocities of the instance (v and w point attributes, respectively) are also incorporated.

Wind Velocity

Ambient velocity of the wind. This operator compensates for wind by subtracting it from values written to the Velocity Field.

Collider Geometry

Name of the geometry data on the simulation object containing the collider. If Collider Type is Individual Volumes, this geometry should include the Surface VDB and Velocity VDB. When Collider Type is set to Packed Sets, this geometry must contain packed primitives for the pieces.

Surface VDB

Name of the signed distance VDB for the collider. If Collider Type is Individual Volumes, this VDB must be present in Collider Geometry; when working with Packed Sets, this is the name of the signed distance field inside each packed piece.

Velocity VDB

Name of the velocity VDB for a deforming collider. If not present, 0 velocities are assumed inside the object.

VDB Name Suffix

This string will be appended at the end of each Surface VDB and Velocity VDB to construct the actual names of these fields. Only used when Collider Type is Individual Volumes.

Instance Geometry

If Collider Type is set to Individual Volumes and this is enabled, the collider will be instanced at every point of the specified geometry data. P (position), orient (unit quaternion for orientation), and pivot (pivot location for rotations) point attributes on the instance geometry affect the placement of each instance. v and w (linear and angular velocities) attributes are also incorporated into the collider’s velocity.

If Collider Type is set to Packed Sets, this geometry must contain instance points for the packed sets. In addition to the placement attributes listed above, each instance point must have a name attribute to identify its piece.

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