Gray polygon appears in render/camera view but not user perspective I'm working on an assignment for an animation class and there is a gray polygon appearing in my camera persp view and in my renders and I cannot figure out what is causing it.

Here is the blend file: http://www.pasteall.org/blend/27989
The grey 'polygon' you see is the background colour. What is happening is your camera clipping end distance is set too low. So any geometry beyond the clip distance is not rendered. Resulting in what you see above.

To fix, simply select the camera and set the Clip distance to a higher value.