GLLEQUAL

GL_LEQUAL is an OpenGL depth test function used with the depth testing mechanism to determine whether a fragment should be drawn based on its depth value. It is one of several depth comparison functions defined by the OpenGL specification and is typically used via the glDepthFunc function, for example: glDepthFunc(GL_LEQUAL).

When GL_LEQUAL is active, a fragment passes the depth test if its depth value is less than or equal to the value currently stored in the depth buffer at the corresponding pixel location. If the test passes, the fragment may update the depth buffer (subject to depth writes being enabled) and be written to the framebuffer; if it fails, the fragment is discarded. The depth test is performed after rasterization and before the fragment’s color is written, and it interacts with the depth mask that controls whether the depth buffer is writable.

GL_LEQUAL is commonly used to handle surfaces that are on or very near the same depth, helping to reduce visible gaps due to depth precision issues (z-fighting). It is often paired with depth buffer clearing and proper projection to maintain consistent rendering results.

Compared to other depth functions, GL_LEQUAL allows fragments with depth equal to the stored value, whereas GL_LESS requires a strictly smaller depth, and GL_EQUAL requires exact equality. The choice of depth function affects rendering of coplanar or overlapping geometry and can influence the visual outcome in scenes with precision limitations.

In typical use, developers ensure depth testing is enabled with glEnable(GL_DEPTH_TEST) and select GL_LEQUAL as the function with glDepthFunc(GL_LEQUAL).