August 09, 2011, 01:15:09 pm
Z-fighting is caused by a lack of mathematical accuracy in real-time 3D and it's present in most 3D engines to a certain extent. From a layman's perspective, it tends to get worse the further away the camera is from overlapping polygons.
There are two ways to deal with the problem.
In real-time presentations, you can adjust the Depth Offset of the material in question. Be very careful not to drag the slider too far though - you only need to adjust it as far as is necessary to make the z-fighting stop. This solution only tends to work if the camera is relatively close to the overlapping polygons.
In movies, you can get rid of z-fighting quite easily once you've made the clip (I assume you've zoomed out quite a lot and the camera is quite high up):
1) New effect -> Scene Effects -> Camera Clip Planes
2) Increase the "Near Plane" slider until the z-fighting is gone.
The rule of thumb is that the closer the "Near plane" is to the eye position and the greater the distance between the "Near" and "Far" camera clip planes is, the more z-fighting you're likely to encounter.