VDB Potential Flow computes how air will flow around obstacles by solving for the closest divergent free velocity field. While this does not create any turbulence, it is effective for allowing particle streams to anticipate collisions and avoid them.
The result is output as a vec3 VDB named
flowvel. The other
VDBs are passed through unchanged.
Note that this is a static solve - there is no history to the field so it may change substantially given slightly different colliders.
The first scalar VDB in this group is used as the collision to compute the flow around. If it isn’t a SDF, it’s activation will be used instead.
NOTE: Only the first VDB is used. If you have multiple colliders, sample them into a single VDB before processing.
The first vec3 VDB in this group is used as the velocity of the collision objects. It is thus only used at the collision boundary to set the solved velocities at those locations.
Only perform the computation in the region specified by this mask. The mask is provided on the second input.
Domain Mask Type
How to treat the mask.
Only process voxels within the the mask.
Process all voxels except those in the mask.
The potential flow will be computed until the specified tolerance is reached. However, some systems may never converge. This caps the number of iterations that are run before terminating the solve.
The potential solve is considered converged when the magnitude of the absolute error is below this value. If no tolerance is specified, 1e-20 is used.
Use World Space Units
If enabled, use world space distances to determine the bandwidth around collisions to compute the potential flow.
Distance in voxels around the collisions to compute the potential flow. Beyond this range the air is assumed to be undisturbed, so this also controls how tightly the air flow will wrap the collider.
Distance in world space around the collisions to compute the potential flow. Beyond this range the air is assumed to be undisturbed, so this also controls how tightly the air flow will wrap the collider.
Direction and magnitude of the default background velocity field. This is applied across all voxels.
Apply Background Velocity to Flow Field
Include the background velocity in the output
flowfield. If not set,
flowfield will provide the difference between the background
velocity and the solved velocity.
Output the scalar potential field, that can be thought of as pressure.
This scalar VDB is called