Pyro Velocity Scale Force Copernicus node

Scales fluid velocity based on the fluid’s current speed.

On this page	Parameters Force Control Mask Angle Mask Axis Mask Inputs Outputs
Since	22.0

Note

Although COP Pyro is in COPs, you need DOP level permissions to use it. This means that COP Pyro is not available in Houdini Core, but only in Houdini FX, Houdini Apprentice, Houdini Indie, and Houdini Education.

This node scales the fluid velocity based on its current speed, providing controls for either slowing down or speeding up the motion of the simulation.

Parameters ¶

Signature

The VDB type that the source accepts.

See Signatures for more information.

Activation

Turns this the effect of this node on and off. This node is only active when this value is 1.

Force ¶

Threshold Range

Maps the threshold field from this range to Scale at Min Threshold and Scale at Max Threshold.

If the threshold field is a Vector VDB, its length is used.

Scale at Min Threshold

The scale applied at the minimum value of Threshold Range.

Apply Scale Below Threshold Min

When turned off, scaling has no effect where the threshold field is less than the minimum value of Threshold Range. This can help prevent motion from speeding up indefinitely or coming to a halt.

Scale at Max Threshold

The scale applied at the maximum value of Threshold Range.

Apply Scale Above Threshold Max

When turned off, scaling has no effect where the threshold field is greater than the maximum value of Threshold Range. This can help prevent motion from speeding up indefinitely or coming to a halt.

Remap Scale

Enables the Scale Ramp, which maps Threshold Range to Scale at Min Threshold and Scale at Max Threshold.

Scale Ramp

Controls how values within Threshold Range are mapped between Scale at Min Threshold and Scale at Max Threshold.

Control Mask ¶

Control Volume

Mask out the effect using the control field. Control fields are usually used the same way as masks, and represent a smooth engagement of the effect.

Control Range

The value of the control field is mapped from this range to 0-1 and applied as a multiplier on top of Scale. The default 0 to 1 range is designed to concentrate the effect on regions with higher control field values. When the control field is a Vector VDB, this value represents the length of the given vector field.

Use Ramp

Turns on the Control Ramp, to change how the control field should scale the effect between the minimum and maximum values of Control Range.

Control Ramp

This ramp controls how the control field values are mapped between the minimum and maximum values of Control Range.

Angle Mask ¶

Angle Mask

Mask out the effect by the angle between the velocity field values and a direction vector.

Angle Direction

The reference vector used to calculate the angle deviation against the velocity field.

Spread Angle

The value of the calculated angle is mapped until this angle range to 1-0 and applied as a multiplier on top of Scale. At the default 90 degrees, the effect is strongest where the vectors align, and gradually diminishes to zero as the angle reaches this value.

Use Ramp

Turns on the Angle Control Ramp, to change how the angle deviation should scale the effect between the aligned vectors and the given Spread Angle.

Angle Control Ramp

This ramp controls how the angle deviation is mapped between the aligned vectors and the given Spread Angle.

Axis Mask ¶

Axis Mask

Mask out the effect along an axis direction. Rather than requiring the construction of VDBs to represent this, this allows direct specification of the world space range over which the effect is to be scaled.

Axis Direction

The reference vector along which the effect will be masked.

Axis Range

The position along the axis mask is mapped from this range to 0-1 and applied as a multiplier on top of Scale.

Use Ramp

Turns on the Axis Control Ramp, to change how the position along the axis should scale the effect between the minimum and maximum values of Axis Range.

Axis Control Ramp

This ramp controls how the position is mapped between the minimum and maximum values of Axis Range.

Inputs ¶

Vector VDB to use as the original velocities.

direction

A Vector VDB allowing per-voxel control of the force direction.

threshold

A Float or Vector VDB to use as a threshold field. If it is a Vector VDB, its length is used.

control

A Float or Vector VDB to use as a control field. If it is a Vector VDB, its length is used.

angledir

A Vector VDB allowing per-voxel control of the angle mask direction.

Outputs ¶

The modified velocities after velocity scale force is applied.

Parameters ¶

Force ¶

Control Mask ¶

Angle Mask ¶

Axis Mask ¶

Inputs ¶

Outputs ¶

Copernicus nodes