Should I worry about shading problem from bevel + triangulation?

bitinn

A quick question:

When dealing with a bevel model, if I don't add additional edge loops, I often find the model show some shading problem after triangulation (see bottom right model).





But I am baking from a high, the end result seem to be the same.




Thin triangles is unavoidable, so is the shading problem on low (before bake), something I should worry about?

bitinn

Sorry to bump this thread, after reading many old threads I finally realise I can fix the shading issue by locking normals before triangulate.

My question is now:

- Those thin triangles created from triangulation. One would suggest I just need more edge loops, but more edge loops is no better than thin triangles overdraw, as they both cost GPU. So should I care?

- I also want to double confirm that, given a normal map and a fixed triangulation, the mesh normal on the low poly doesn't matter, is it true?

- I believe mesh normal on low poly is only used for baking raycast (if you don't have a specific cage mesh), but nowadays we use averaged normal for baking anyway, so is low poly mesh normal mostly moot?

ZacD

Just terminate the corners on the top face near the corner so the top looks like a square with a bunch of edges coming out of the corners. 

Lots of small tris is bad. Small ones and long ones are both bad. 

Mesh normals can increase the vertex count, but isn't a big deal. The biggest thing to worry about is splits in the mesh normals require a UV split if you want to use a normal map.

The low poly normals directly affect the bake. 

bitinn

ZacD said:

Just terminate the corners on the top face near the corner so the top looks like a square with a bunch of edges coming out of the corners. 

Lots of small tris is bad. Small ones and long ones are both bad. 

Mesh normals can increase the vertex count, but isn't a big deal. The biggest thing to worry about is splits in the mesh normals require a UV split if you want to use a normal map.

The low poly normals directly affect the bake. 

Thx!

About terminating the bevel corner edges, I can think of "Merge to Center"; maybe there are better tricks?






"Mesh normal": I really mean a mesh with only soft edge (aka 1 smoothing group), tools like Substance Painter will use average normals from the low instead of the actual normals to bake. So I am not sure how else it affects the bake.

ZacD

Much better, that's generally considered the optimal way to deal with that problem. 

Substance Painter uses only average normals for the cage, not for the lowpoly.

bitinn

ZacD said:

Much better, that's generally considered the optimal way to deal with that problem. 

Substance Painter uses only average normals for the cage, not for the lowpoly.

Thx!

On the subject of normal map: can I think of it as a per-pixel patch? So given a low poly and its mesh normals, we want to adjust the result surface normal to match the high poly as much as possible.

And that's why we generally want low silhouette to match high, so normal map doesn't have to do "extreme patching".