Hi there- 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-fa…

Hi Dave, This is a known issue. https://mcneel.myjetbrains.com/youtrack/issue/RH-10076 I’ll mention this to the developer again. – Dale

Thanks, Dale! It fails rarely…but does indeed.

This method don’t work at all in my case - http://developer.rhino3d.com/5/api/RhinoCommonWin/html/M_Rhino_Geometry_Mesh_IsPointInside.htm Mesh is closed also tolerance here no matter if ZeroTolerance / Rhino.RhinoDoc.ActiveDoc.ModelAbsoluteTolerance / 1000 also no change with true or false always i…

I’m not sure what your mesh looks like. The algorithm simply creates a line from the test point to a point know to be outside of the mesh. An intersection is run on this line with the mesh and if the number of intersections is an odd number, true is returned. I’m sure there is a more robust approach…

Thanks @stevebaer for suggestion. I’ll try with MeshLine one. Btw. i’m making quickhull algorithm so there’s a lot of points on edge and that’s probably the issue here.

[image] D-W: i’m making quickhull algorithm The Waterman Polyhedra add-on included a QuickHull implementation - and it’s available in Grasshopper… – Dale

@dale i use GH only for quick prototyping code i needed this in c# and now i have partially with IsPointInside and if something is giving false it just falls to closest point with tolerance quick and dirty workaround but it works finally.

Mesh.IsPointInside() persistent bug

Rhino Developer

brian (Brian Gillespie) March 24, 2026, 9:59pm 9

RH-10076 is fixed in Rhino WIP

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Mesh.IsPointInside() persistent bug

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