vdb_influence

The VDB influence applies a velocity from a VDB file to the simulation velocity. For high drag values with a force_scale of 1.0 the simulation will exactly follow the VDB velocity.

To use this node, plug its output into the influences input of a simulate node like simulate_aero, simulate_particles, or simulate_mpm.

Inputs

influence

One may optionally connect an influence field out_influence into this port. For example a mask_influence node could be connected to mask the effect of this influence. Any number of influence fields may be added to the daisy chain to build a complex field.

enable

Turn off to disable the effect. Disabling makes it a pass through node. Note that any other influence fields connected to the influence input port will still be active when this is disabled.

force_scale

This is multiplier of the velocities from the vdb_file to use for applying as acceleration.

You can connect a float, ScalarField, float3, or VectorField. VectorField and float3 values modulate the effect differently in each axis.

filename

The base filename of the VDB file.

directory

The filepath to the folder the VDB file is in.

force_attribute

This is the name of the property from the VDB file to use for velocity. It should be a float3 property.

start_frame

The beginning of the frame range to use from the VDB file.

end_frame

The end of the frame range to use from the VDB file.

frame_offset

This is an offset from the current frame to apply. So if frame_offset was 100, then frame 1 from the VDB file would occur at frame 101.

position_scale

This scales the size of the VDB field.

position_offset

This translates the position of the VDB field.

drag

This will dampen the current simulation velocities, resulting in less velocity buildup over time. High values of drag will fully replace simulation velocity with the VDB acceleration, instead of continually adding in the acceleration. To have particles follow the VDB flow exactly, use high drag and make the force_scale 1.0. You can connect a ScalarField to vary the effect over space.

Outputs

out_influence

An output influence object that one can connect to simulation nodes or other influence nodes.