Houdini Volume Sample & Volume Gradient

In Houdini, a VolumeSample is a way to access the data stored within a volume at a specific point. Volumes in Houdini represent 3D grids of values, such as density, temperature, or velocity, and a VolumeSample allows you to query the value at a given position within the volume. For example, you can use a VolumeSample to get the value of a voxel (the 3D equivalent of a pixel) at a certain coordinate. This is useful in fluid simulations, procedural generation, and other tasks where 3D data needs to be read or manipulated based on position within the volume grid.