Does some function e.g. fastPointMetrics produce sum of vertical "pillars" of voxels to form a "kind of CHM"?

[mavavilj]

Does some function e.g. fastPointMetrics produce sum of vertical "pillars" of voxels to form a "kind of CHM"?

I.e. it calculates how many filled voxels there are along z-axis for each x-y -axis rectangle.

[spokswinski]

We make a "kind of CHM" by using the grid_canopy funtion in lidR after normalization and voxelization, but that just gives us a raster with heights, not how many voxels in a column.