It looks like Mesh.IsPointInside() will occasionally fail, when a test vertex strikes the inclusion mesh precisely on an edge. Writing one from scratch following David’s logic from this thread over on the old GH forum: http://www.grasshopper3d.com/forum/topics/mesh-ispointinside-always-false reproduces the error. I made a quick fix that does a second test based on another arbitrary vector and then determines if the number of intersections for either test is an odd number…doubles the effort, but seems to work. In any event, it’s worth knowing that this bug is persistent.
This is a known issue.
I’ll mention this to the developer again.
Thanks, Dale! It fails rarely…but does indeed.