Surface Thickness Property Direction


Why does the render thickness applied to surfaces act in the opposite direction to the surface normal? OffsetSrf goes in the surface normal direction.



When you want to add thickness to a solid you probably want that on the inside, away from the normal. Your surface defines the outside of your object. Therefor you want the thickness to happen on the inside. This is why thickness in opposite direction of the normal.

If you want thickness along the normal make it negative.

Note that thickness is a mesh trick. It doesn’t give you a closed polysurface. Thickness applied to a plane still ends you up with a plane, not a box.

Thanks for the explanation @nathanletwory. In my naval architecture world we model the hull surfaces to the moldline (mold surface) and offset in the normal direction for metal boats, otherwise we end up clashing into internal structure.

Understood about the mesh trick, I was testing a theory about clash detection and sectioning with an extracted mesh when I noticed the direction didn’t align with my world view.

I suppose for your use case you’d then want to use the negative thickness. Does that work for you?