Unwanted artifacts in render

Hi,

I want to render an animation of a spinning pyramid, but there is a mysterious black cube present in some of the rendered frames (not all frames). This cube is not present in the scene. At first, I rendered the animation as PNG with RGBA, then I tried to render it without alpha channel, but to no avail.

Here’s an example of a frame with the mysterious black cube present. (The pyramid was at first a cube; maybe that has something to do with it.)


Claus

P. S.: Here’s the .blend file:

pyramide.blend (427 KB)

I just rendered the animation in your file and am not able to replicate your issue: All frames are perfectly alright…

In your signature it says that you use Blender 2.76b on ubuntu 16.04 LTS - that’s not the Blender version from the ubuntu repositories, is it?

You should always use the newest “official” Blender from blender.org, which is 2.79b at the moment. Repo builds often suffer from repository maintainers not being completely knowledgeable concerning the respective software packages, which can lead to unexpected issues.

Tested this on Win8.1 Blender 2.79 with no issues, no black cube. You do have some unmerged verts in your object but that doesn’t affect anthing. (To get rid of them, go into edit mode, w->remove doubles. However, tested on 2.76 I get the same problem. Any particular reason you’re not using 2.79?
Removing the doubles in 2.76 does sort the problem. My guess, it’s getting itself all confused over the face normals, by eliminating the overlapping verts, it allows Blender to correctly calculate them.

I was using 2.76b because it’s included in the Ubuntu repositories. Now that I downloaded 2.79b, the problem isn’t there anymore. I was able to render the animation without a problem. Thanks for the recommendation!

Claus