depthtest

Depth testing, also known as the Z-test, is a rendering technique used in 3D computer graphics to determine which surfaces are visible and which are hidden. When rendering a 3D scene, multiple objects can occupy the same space from the viewer's perspective. Depth testing ensures that only the closest object to the camera is rendered at any given pixel, preventing objects from incorrectly appearing in front of others when they should be behind them.

The process typically involves comparing the depth value of a new pixel being rendered with the depth value of the pixel already stored in the depth buffer (or Z-buffer). The depth buffer is a memory area that stores the depth information for each pixel on the screen. If the new pixel's depth is closer to the camera than the existing pixel's depth, the new pixel is drawn, and its depth value is updated in the depth buffer. If the new pixel is further away, it is discarded, and the existing pixel remains visible.

Depth testing is crucial for creating realistic 3D scenes. Without it, objects would render in an arbitrary order, leading to visual artifacts like seeing through solid objects or having closer objects obscured by farther ones. This technique is a fundamental part of most 3D rendering pipelines, implemented in graphics hardware to efficiently manage visibility and occlusion.