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The Volume Reduce operation reduces all of the voxel values of a volume into a single value. This can be used to determine properties of a volume, such as the minimum or maximum value.
Volume reduce will also blur the volume; however, it is different from Volume Blur because volume reduce is an intermediate step, not an end result. It will affect the whole volume, not just pieces of the volume.
This node currently only works with standard Houdini volumes. It does not work with VDBs.
The volume primitives to be reduced.
The types of reduction to be performed.
Used by the median reduction method to determine which percentile voxel will be extracted.
Depending on the dimensions of the input field, you may want to also apply an additional scale to make the result independent of your voxel resolution.
Note that tapered volumes do not have a consistent scale so their behavior is less well defined.
Do not apply any scaling effects.
By Voxel Length
Scale by the length of a voxel, defined as the cube root of the voxel’s volume.
By Voxel Area
Scale by the area of the voxel, defined as the square of the cube root of the voxel’s volume. Use this to turn the result of an SDF to Surface into a surface area.
By Voxel Volume
Scale by the volume of the voxel. Use this to turn the result of an SDF to Fog into a volume.
Store Results In
Determines where the final computed value is stored. If it is set to volume, the volume is replaced by a constant volume of the given value. The volume will also be changed to streaked border condition, so no matter where it is sampled the reduced value will be returned.
The other result choices will store on the appropriate attribute. If the attribute does not exist, a single float attribute of the given name is created. In the case of a detail attribute, the detail attribute will be of the same size as the number of volumes involved in the reduction.
The name of the attribute to store the value in.
The local variable to create for the attribute. If blank, the attribute in upper case will be used.
This example shows how to use the Volume Reduce SOP to compute the barycenter of a 3d object.
The following examples include this node.