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I'm not sure this is the right place to ask this, but I hope so. I'm new to 3D modeling and I've just learned Blender. I was following this tutorial on creating a watch and noticed that when I rendered the watch, some pieces were messed up. I can't explain it well, so here's a picture:

Blender Render issue

I don't know if it's a problem with my World texture, the object, or the object's texture/material, so I can't even guess how to fix it. What causes this? Is it possible to fix it?

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up vote 7 down vote accepted

It looks like Z-fighting, which is caused by overlapping faces in your model.

From Wikipedia:

Z-fighting is a phenomenon in 3D rendering that occurs when two or more primitives have similar values in the z-buffer. It is particularly prevalent with coplanar polygons, where two faces occupy essentially the same space, with neither in front. Affected pixels are rendered with fragments from one polygon or the other arbitrarily, in a manner determined by the precision of the z-buffer. It can also vary as the scene or camera is changed, causing one polygon to "win" the z test, then another, and so on. The overall effect is a flickering, noisy rasterization of two polygons which "fight" to color the screen pixels.

From looking at the tutorial you linked, the most likely place for this to have happened is in the Mirror modifier on the overlapping pieces. Ensure that the object origin is in the right place relative to the geometry, so the the geometry does not extend past the origin along the mirror axis:

enter image description here

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I moved the object over a little on the Y-axis and that fixed it! Thanks a lot! –  Abluescarab Dec 11 '13 at 8:44
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