Since the initial merge of the geometry nodes project, the modifyPointCloud
function already was already modifying a geometry set. The function wasn't
renamed back then, because then the merge would have touched many
more files.
Ref T83357.
The issue was that the volume for the current frame
might not have been loaded already by the time the
modifier runs.
The solution is simply to make sure that the volume
is loaded. This is similar to the Volume Displace modifier.
This modifier is the opposite of the recently added Mesh to Volume modifier.
It converts the "surface" of a volume into a mesh. The "surface" is defined
by a threshold value. All voxels with a density higher than the threshold
are considered to be inside the volume, while all others will be outside.
By default, the resolution of the generated mesh depends on the voxel
size of the volume grid. The resolution can be customized. It should be
noted that a lower resolution might not make this modifier faster. This
is because we have to downsample the openvdb grid, which isn't a cheap
operation.
Converting a mesh to a volume and then back to a mesh is possible,
but it does require two separate mesh objects for now.
Reviewers: brecht
Differential Revision: https://developer.blender.org/D9141
