Houdini 20.0 Nodes Geometry nodes

Volume Feather geometry node

Feathers the edges of volumes.

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Since 11.0

The Volume Feather operation smooths the edges of the scalar data in volume primitives. This is done either in an inwards or outwards direction. It sets the maximum rate of change in the volume, clamps either increasing or decreasing transitions, and can be thought of as a one-sided blur.

Note

This node currently only works with standard Houdini volumes. It does not work with VDBs.

Parameters

Source Group

The volume primitives to be feathered.

Feather Mode

The feather operation limits the amount of change that the volume can have over space. The Feather Mode controls how to compute this rate.

Note that the clamp on the change is one-sided.

Change per Distance

Over a unit distance, the volume can only change by this amount.

Change per Voxel

Over a single voxel, the volume can only change by this amount.

Distance for Unit Change

Over this distance the volume can only change by a unit amount.

Voxels for Unit Change

Over this number of voxels, the volume can only change by a unit amount. This is useful for proscribing how many voxels a unit-valued mask would be extended.

Slope Angle

Measures the angle in degrees at which the change is clamped. This is primarily meaningful for heightfields, where it corresponds to the observed slope.

Change per Distance

The distance multiplier factor to use to adjust the change in the voxel value for each unit change in worldspace. Lower decay values will result in a larger feather radius.

Change per Voxel

The distance multiplier factor to use to adjust the change in the voxel value for each voxel traversed. Lower decay values will result in a larger feather radius.

Distance for Unit Change

The distance at which the volume is allowed to change by one unit value.

Voxels for Unit Change

The number of voxels at which the volume is allowed to change by one unit value.

Slope Angle

The maximum permissible slope of a heightfield.

Feather from High to Low

The slope-clamping is done on a one-sided fashion, and this determines which side is clamped. Feathering from High to Low will not allow the volume’s values to decrease faster than the clamped rate. The opposite does not allow the volume’s values to increase faster than the clamped rate.

If this voxel has value V, and is distance D from another voxel of value W, the result is MAX(V, W-decay*D) for High to Low and MIN(V, W+decay*D) for Low to High. The result is for fog volumes to grow in the High to Low mode and shrink in the Low to High mode.

Autodetect 2d Volumes

2D volumes are not feathered along their thin axis. However, sometimes you may have a 3d volume that has collapsed into 2d, and want it to still be feathered in the 3rd dimension.

Override Border

Overrides the volume’s border conditions for the feather.

Use Volume

Use the volume’s border settings.

Constant

Treat exterior voxels as having a constant value.

Repeat

Wrap voxel values from one side of the volume to the other.

Streak

Extend boundary voxels.

Border Value

The value of the border to use when overridden with constant border conditions.

Examples

volumefeather Example for Volume Feather geometry node

This example shows how to use the Volume Feather SOP to smooth sharp volumes either in a purely outwards or purely inwards direction.

See also

Geometry nodes