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The points in the first input that will have their attributes set from the volume values.
The volumes in the second input to use for sampling the attribute values. If there are not enough volumes for the size of the attribute, the volumes will be re-used in turn.
For convenience, volumes may be specified directly by "name",
ie, the value of their name attribute. Thus the density
volume can be retrieved with "density" and the velocity set of
three volumes with
These parameters control what attribute the node saves the volume information into. They also control what type of attribute the node creates. If the attribute already exists in the first input, the node ignores the creation parameters.
Name of the attribute.
Create Variable Mapping
Specifies whether to create a local variable for the attribute.
The name scripts/expressions can use to refer to the attribute as a local variable. If you leave this blank, Houdini will use the name of the attribute in all caps.
The sort of attribute to create. The Vector attribute is distinct from a triple of floats because it is often transformed like a normal.
The number of components in the attribute type. For example,
setting Attribute type to "Float" and Attribute size to
1 creates a simple scalar float attribute.
The default value of the attribute. Four text fields are always
visible but the node only uses the number of fields corresponding
to the Attribute size. If the size is greater than
node cycles back through the four fields.
Instead of directly copying the value from the volume, you can optionally map the to get the volume values into a different range and/or scale the values using ramps.
The volume value will be remapped so that this min/max pair become the 0..1 interval prior to applying any of the ramps.
Map Volume to Value
Specifies a ramp to apply to all channels equally. Out of range values will either be clamped or wrapped according to the mode.
Map Volume to Vector
Specifies a color ramp. Each channel of the color ramp is applied to each volume in turn, so if there are three volumes, the first will get the red, the second green, and third blue ramps. However, since volumes are reused, this means that if you have a single volume you can color it using the vector ramp.
The ramps output a 0..1 interval. This is then remapped to the min/max given in the output range.
Here’s a simple example showing how you can deform a volume. First create a 3d grid of points with the box sop with divisions matching the resolution of the volume. Next, transfer the density from the volume on those points. Finally, the points can be deformed any way you want, and then you can create an empty volume and fill it with the densities from the points.