AO and Blender's triangulation

So I was playing around with ambient occlusion and compositing and found this (Blender Internal renderer):

Both cubes consist of quads only, not triangles. The right one is subdivided a few times.

As you can see, for some reason Blender’s conversion of quads to triangles results in small artefacts in either the render or the AO pass that become visible when combining image and AO in the appropriate way. Weird.

(and yes, the name of the attachment is wrong: It should be triangulation:p)


Tesselation.blend (59.6 KB)

So, why not submit to the bug tracker?

I’m not sure if it really is a bug or just a rendering artefact.

I can’t see what the bug is??!

What exactly did you differently? Whenever I render ambient occlusion, it never shows up like that.

I composed the AO pass with the composite pass using nodes. When including AO in the composite pass, everything looks just as it’s supposed to. That’s why I’m not sure if it’s a bug.

Did you try the attached .blend?

This is what I get when I render your blend.


Blender 2.49a
Mac OSX 10.5.7

I get the same thing as OP (Jonathan_S)

I’m using blender 2.49a 64bit & python 2.61

Eureka! I found it!
It’s the value node - Blender is trying to pull the value data from a blown-out black part and can’t.
Just switch the inputs to value node around and you should be fine.
That’s what I did and it seemed to work. dodge also had the same effect when the inputs were reversed - the compositor can’t pull any data from there so it shows triangles - I think this is alot like trying to devide by zero :yes:.


Tesselation.blend (204 KB)