glDepthFuncGLLEQUAL

glDepthFuncGLLEQUAL is a constant used in OpenGL to specify the depth comparison function. When setting the depth function using glDepthFunc, GL_LEQUAL indicates that a fragment should be written to the depth buffer if its depth value is less than or equal to the current depth value in the buffer. This is a common setting for depth testing, allowing objects to be rendered correctly in front of or at the same depth as objects already drawn.

The depth buffer, also known as the Z-buffer, stores depth information for each pixel. When rendering a new fragment, its depth value is compared against the value already stored in the depth buffer at the corresponding screen coordinates. The glDepthFunc function determines the criteria for this comparison. GL_LEQUAL is a standard option that ensures that closer or equally distant fragments are drawn.

In practice, using GL_LEQUAL is crucial for achieving correct occlusion in 3D scenes. If a scene contains multiple objects at the same depth, GL_LEQUAL will ensure that whichever object is rendered last at that depth is the one that remains visible. This is often used in conjunction with a depth buffer clear operation at the beginning of each frame to reset the depth values. Other depth comparison functions include GL_NEVER, GL_LESS, GL_EQUAL, GL_GEQUAL, GL_GREATER, GL_NOTEQUAL, and GL_ALWAYS, each providing different behaviors for fragment visibility based on depth.