Artifact on corner of plane in render

I have a problem with an artifact/edge showing up on a corner of a plane I have rendered.

http://www.petrolia.com/blender/artifact.png

Anyone know what I might be doing to cause this?

The (zipped) blend file is here.

Iso

I gave a look at your blend, and I managed to fix it’m having troubles at uploading the file on my space, so I’ll tell you how to fix it. It seemed to be a problem with lights. Why so many? delete them (keep the lamp near the cube), and add an Hemi light. Put it over your scene with the dotted line pointing downward (like you did for the arealights), set Distance to 20 and energy to 0.5. Position the Hemi so that the dotted line goes trough the plane just a bit.

A Hemi light casts a uniform light on your scene in the direction indicated by the doted line. Adjust the settings untill the difference between plane and background is not noticeable in the render.

You aren’t doing anything wrong. The regular renderer calcs renders in several passes for speed – this can lead to some artifacts especially when the world and object have the same colour and also with halos. The unified renderer renders the scene only slightly slower in a single pass but gets rid of the artifacts. So I suggest you try the unified renderer (render buttons -> format panel).

GreyBeard

PR:
Thanks for your fix. That fixes my artifacts! I was trying to match the entire rim of the plane edge to the background without effecting my cube’s lighting. That’s why I used so many lights. The only downside to the hemi, is that it lights my model too. But that can be compensated for pretty easily.

GreyBeard:
Also an excellent fix! It handles every contingency! I never really had a reason to use the unified renderer until now. Very cool indeed.

Thanks guys,
Iso