Ramps over multiple objects

I have two objects that reference the same mesh and material (opposite sides of a car bonnet). However, when I apply a ramp in Blender 2.41 to get the desired shading, a funny thing happens. The ramp only applies properly to the side closest to the camera. This means that the ramp stops at the border between the two objects.

Does anyone know why the ramp doesn’t appear to simply flow over the two objects? After all, they both use the same texture and they are directly adjacent to one another.[/img]

Posting an image or the .blend might help someone to help you.

Unfortunately I don’t have a place where I can upload an image at the moment and the forum wont let me attach one - unless someone knows a way?

Oh actually I figured out a way. Here we go:


As you can see, its ramping properly on the right (note the bright white from the clearcoat) and not on the left (i.e. no bright white). Anyone got any ideas?

I have an idea. If you use the mirror modifier it probably won’t work and you say that it has the same texture and textures and ramps (as far as I know) ain’t possible too make on the same material but the Ramp should be the one that appear.

Is there a particular reason you don’t just join the 2 halves? That would surely solve your problem.

I have both halves as seperate objects so that I can mirror them but have them reference the same mesh. That way, when I update one side, it updates the other automatically. Makes modelling a lot faster.

Oh and robin, sorry. When I said texture I meant material. The material is just red with a Minnaert diffuse shader, Phong specular shader, an additive specular ramp and raytraced mirroring.

What I don’t understand is the Ramp should be a function of the angle of incidence and reflection of the light on the surface. So why does it apply differently across two objects with the same material parameters and, at the point where they meet, a similar surface angle?

Cire, I just tried joining the two halves. It still happens! weird!? I also tried making the materials and objects single-user. Same again. Really stuck in a rut here.

If you want to send me the .blend, maybe I can help you figure this out.

E-mail is [email protected]

I checked the .blend & found the source of the problem.

It seems that the minor difference in the angles of your (2-part) mesh’s normals combined with the camera/lighting angles used created the abrupt shading change.

The change was not a ramp shader problem, but was related to the specular reflection (your confusion lay in the fact that the ramp shader was applied to the specular reflection).

When joined & connected the shading is correct, as seen below. It just so happens that your particular scene setup results in the specular highlight ending at the center-point of the hood (even when smoothly shaded).


Keep modelling the way you have been, but make sure you connect the vertices at the seam after joining the meshes together.

BTW: To remove unrelated artifacts in the mesh rendered above, certain faces were removed at the front of the hood (skinny/duplicate faces at the edge & the bottom faces curving under the lip).

Thanks for looking in to it. I thought that may be the case but I didn’t think such a small variance in angle would make such a large difference. Now I understand.