But for coplanar polygons, the problem is inevitable unless corrective action is taken.Īs the distance between near and far clip planes increases and in particular the near plane is selected near the eye, the greater the likelihood exists that z-fighting between primitives will occur. The more z-buffer precision one uses, the less likely it is that z-fighting will be encountered. This problem is usually caused by limited sub-pixel precision and floating point and fixed point round-off errors. The overall effect is a flickering, noisy rasterization of two polygons which "fight" to color the screen pixels. It can also vary as the scene or camera is changed, causing one polygon to "win" the z test, then another, and so on. 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 is particularly prevalent with coplanar polygons, where two faces occupy essentially the same space, with neither in front. Traditionally, the farther pixel would be discarded. This then means that when a specific pixel is being rendered, it is nearly random which one of the two primitives gets drawn in that pixel because the z-buffer cannot distinguish precisely which one is farther from the other. This would cause them to have near-similar or identical values in the z-buffer, which keeps track of depth. Z-fighting, also called stitching, is a phenomenon in 3D rendering that occurs when two or more primitives have very similar distances to the camera.
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