Function meshopt::clusterize::compute_cluster_bounds

pub fn compute_cluster_bounds(
    indices: &[u32], 
    vertices: &VertexDataAdapter<'_>
) -> Bounds

Creates bounding volumes that can be used for frustum, backface and occlusion culling.

For backface culling with orthographic projection, use the following formula to reject backfacing clusters: dot(view, cone_axis) >= cone_cutoff

For perspective projection, use the following formula that needs cone apex in addition to axis & cutoff: dot(normalize(cone_apex - camera_position), cone_axis) >= cone_cutoff

Alternatively, you can use the formula that doesn’t need cone apex and uses bounding sphere instead: dot(normalize(center - camera_position), cone_axis) >= cone_cutoff + radius / length(center - camera_position)

or an equivalent formula that doesn’t have a singularity at center = camera_position: dot(center - camera_position, cone_axis) >= cone_cutoff * length(center - camera_position) + radius

The formula that uses the apex is slightly more accurate but needs the apex; if you are already using bounding sphere to do frustum/occlusion culling, the formula that doesn’t use the apex may be preferable.

index_count should be <= 256*3 (the function assumes clusters of limited size)