Houdini 21.0 Nodes Copernicus nodes

Pyro Build Advection Map Copernicus node

Constructs a flow map from a velocity VDB.

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Since 21.0

Pyro Build Advection Map constructs a vector VDB that stores where each voxel should come from if it were advected by the provided vector velocity VDB.

Parameters

Scale

A global scale on the velocity values.

Scale by Timestep

Scale the velocity values by the timestep.

Integrator

The method used to compute the flow map of the velocity VDB.

Path Trace

The velocity VDB is traced using the the CFL condition to control the step size. This can handle large velocities in a single step.

Average of Two

The velocity VDB is sampled twice, once at the location, and once where that would have come from. The average is used. This provides a fixed-cost and does a better job preserving rotations, but will break up with large velocities.

Maximum Steps

Global clamp on how many steps can be performed. For extremely fast motion this may need to be increased; but it might be better to raise the CFL condition instead.

CFL Condition

How big of a step should be used. This is approximately how many voxels will be stepped during path tracing.

Ambient Velocity

A constant global velocity that the VDBs will also be moved by, in addition to the values in the velocity VDB. This can be used as a wind-effect as it allows the wind to alter speed without affecting local dynamics.

Inputs

v

Vector VDB providing the velocity.

Outputs

map

Vector VDB providing the position the voxel should read from.

See also

Copernicus nodes