Help replicating legacy prim's shading

[Fenix Eldritch]

I'm recreating a prim based avatar into mesh components. For the most part, it's going well. However I have a problem with the shading on the mesh counterparts. Pictured below is a rear view of the head and torso components, mesh on the left and original prims on the right. The shading is considerably darker or lighter on the cylinders that make up the head, neck and shoulder bar. (this picture was taken with Advanced Lighting + Ambient Occlusion enabled, but the issue is even more apparent without it)

Originally, I had everything using smooth shading - and that had similar problems with other ares of the mesh parts. I was able to solve some of that by using Flat shading on the more boxy shapes. But doing the same for these cylinders won't work as nicely, because the faces will become too noticeable.

Is there a trick to making a mesh cylinder shade similarly to a prim?

[arton Rotaru]

Sure thing you will have make any edges hard which are hard on the prims as well. The rest is probably due to a different number of vertices around the circle. Which will result in different vertex normal angles indeed.

[Drongle McMahon]

As Arton said, you need the edges around the cylinder caps to be sharp, while the edges prallel with the cylinder length have to be smooth. You might be able to achieve this by playing with the "Generate normals" and the associated crease angle in the uploader, although that is a blunt instrument.

Better would be to use the facility in your mesh program. In Blender, you can use the edge-split modifier, with edges explicitly marked as sharp (rather than using the angle setting), while the rest of the mesh stays smooth shaded. Even simpler, you can just select the edges and split them (Ctrl+E,D; or Mesh->Edges->Edge Split). Be careful though not to apply a subsurf modifier after splitting either way - that will open up gaps between the split edges.

In other software, I think you have to use smoothing groups. I am not familiar with those, so someone else would have to tell you how.

[Fenix Eldritch]

Ah ha! Thank you Arton and Drongle! Using the Mesh->Edges->Edge Split option in Blender on the cylinder caps achieves the shading effect I was after.

Just for clarification, in this context "sharp" and "hard" mean the same, right? And marking an edge as hard is akin to marking a seam? In the sense that both are used in preperation for another action? (seam is to unwrapping as hard is to the edge split modifier)

[arton Rotaru]

Hard, sharp means all the same, right. While a seam is just a seam on the UV's, which can have also hard/sharp, or soft/smooth edges. It's more a Blender terminology thingy I guess. Terms like "Mark Sharp", or "Mark Seam", which can make it a little bit confusing.