I came across one annoying problem recently involving smoothing groups in models. Mainly 3ds max obj exporter problem. Since I will be using obj format for static meshes, the problem is that when exporting from max to obj format it exports everything except smoothing groups, so entire model looks like it uses one for entire model, and as a result it looks like it is completely smoothed out.

Later i found that a way to avoid this problem is to detach parts of the model that use different smoothing groups so there is no issue. But then I am concerned about memory consumption of this since every detached piece of the model has duplicate vertices in places where it would be connected it smoothing groups were working.

For example if you have cube model with 8 vertices, since it looks wrong in the engine, you would detach each side of the cube and have 6 sides with 4 vertices, and there is the problem i am trying to address.

My question here is - can this pose a threat to performance or memory consumption since there might be many static meshes in the scene? This is considering modern day hardware.

This really depends. It's something you're just going to have to time and see if it's too slow for you or not. If you're trying to get some kind of facet shading, then you can look into alternatives like computing the face normal from the derivative of the position in the pixel shader or computing the face normal in the geometry shader and see if those perform better for you. If facet shading isn't what you want, and you really just want some surfaces to have separate smoothing groups, then there isn't much else you can do than duplicate the edge verts. The extra cost will be a function of how many verts you actually duplicate. If you're only duplicating ~1% of your verts, then you might not notice a huge performance drop. If you're duplicating 100% of your verts, then you might really notice it (if your static geometry is expensive, if not, then maybe even duplicating 100% of the verts won't significantly impact your performance). You really just have to test the performance and ask yourself if the feature is worth the cost.

Hello there.

This sounds like a shader and normal type thing. what I thought smoothing groups was some type value to fake roundness on a sharp bend this is all done in shaders now hey????.. where am I.