Problem with Tangent V Shading + Shadows

I’m getting this strange artifact with raytraced shadows and Tangent V Shading with a simple spotlight:

Can anyone explain this? If I turn shadows off it looks fine, but then I obviously don’t have shadows.

Happens in both 2.49b and 2.56a.

Cheers,
John

i am thinking by the look of it you may have those normals set the wrong direction. (new to here and blender, but it’s what seems most logical to me)

Normals are definitely in the right direction. I’m thinking this is a bug after looking at several other threads. It needs to be reported.

Cheers,
John

Tangent V setting produces artefacts with raytraced shadows. This has nothing to do with normals, its the way it works sadly.

Maybe you can work around this with the node materials.

Looks like the only way, to me, is to take the specular output from a Tangent V node and using a mix node to add it to another object sans specular component.

Cheers,
John

Hi. Yes, this is sadly the way Blender works right now (might be a bug, have not checked). The artifacts are based on the meshes geometry, it treats it as a flat shaded object when it calculates the ray shadows. Because of this I found that if you are able to - that the object is not to big, is not the main subject and taking up most of the picture, your computer has enough ram, etc - you can just up the render levels on the objects subsurf modifier if it has one. That will result in a smoother shadow boundary.