vfill FILE using x:y:z:radius:(<expression>)
The vfill command acts analogously to a plot command except that instead of creating a plot it modifies voxels in the currently active voxel grid. For each point read from the input file, the voxel containing that point and also all other voxels within a sphere of given radius centered about (x,y,z) are incremented as follows:
vfill "file.dat" using 1:2:3:(3.0):(1.0)
Example:
vfill "file.dat" using 1:2:3:4:(VoxelDistance < 1 ? 1 : 1/VoxelDistance)
Note that vfill always increments existing values in the current voxel grid.
To reset them to zero, use vclear.