Zfighting

Z-fighting, or z-fighting, is a rendering artifact in 3D graphics that occurs when two or more surfaces occupy very similar depths at the same screen pixel. Because the depth buffer has finite precision, the depth test cannot consistently decide which surface should be visible, causing pixels to flicker or render as a speckled mix as the scene changes or as the camera moves.

Causes of z-fighting include insufficient depth buffer precision, a wide depth range due to a large distance between the near and far clipping planes, and geometry that is coplanar or nearly coplanar. It is common where two polygons share an edge or overlap, such as terrain seams, architectural details, or decals drawn on top of another surface.

Mitigation techniques focus on increasing the reliability of the depth test. Options include using a higher-precision depth buffer (for example 24-bit or 32-bit depth), reducing the depth range by adjusting the near and far planes, or employing a reversed depth buffer to maximize precision for closer objects. For coplanar or overlapping surfaces, a depth bias or polygon offset can push one surface slightly away in depth to prevent fighting. Merging coplanar geometry into a single polygon, or reworking the scene so that overlapping surfaces are not rendered at identical depths, also helps. In some cases, rendering overlays or decals with the depth buffer disabled or using a stencil test can avoid z-fighting in those layers.

Z-fighting is a common concern in real-time rendering and can often be mitigated with careful management of depth precision, geometry, and rendering order.