glDepthFunc - specify the value used for depth buffer comparisons

glGet() with argument GL_DEPTH_FUNCglIsEnabled() with argument GL_DEPTH_TEST

voidglDepthFunc(GLenumfunc);

       Copyright © 1991-2006 Silicon Graphics, Inc.
       Copyright © 2010-2014 Khronos Group

[FIXME: source]                                    11/18/2024                                    GLDEPTHFUNC(3G)

glDepthFunc specifies the function used to compare each incoming pixel depth value with the depth value
       present in the depth buffer. The comparison is performed only if depth testing is enabled. (See
       glEnable() and

       glDisable of GL_DEPTH_TEST.)

       func specifies the conditions under which the pixel will be drawn. The comparison functions are as
       follows:

       GL_NEVER
           Never passes.

       GL_LESS
           Passes if the incoming depth value is less than the stored depth value.

       GL_EQUAL
           Passes if the incoming depth value is equal to the stored depth value.

       GL_LEQUAL
           Passes if the incoming depth value is less than or equal to the stored depth value.

       GL_GREATER
           Passes if the incoming depth value is greater than the stored depth value.

       GL_NOTEQUAL
           Passes if the incoming depth value is not equal to the stored depth value.

       GL_GEQUAL
           Passes if the incoming depth value is greater than or equal to the stored depth value.

       GL_ALWAYS
           Always passes.

       The initial value of func is GL_LESS. Initially, depth testing is disabled. If depth testing is disabled
       or if no depth buffer exists, it is as if the depth test always passes.

GL_INVALID_ENUM is generated if func is not an accepted value.

       glDepthFunc - specify the value used for depth buffer comparisons

       Even if the depth buffer exists and the depth mask is non-zero, the depth buffer is not updated if the
       depth test is disabled. In order to unconditionally write to the depth buffer, the depth test should be
       enabled and set to GL_ALWAYS.

func
           Specifies the depth comparison function. Symbolic constants GL_NEVER, GL_LESS, GL_EQUAL, GL_LEQUAL,
           GL_GREATER, GL_NOTEQUAL, GL_GEQUAL, and GL_ALWAYS are accepted. The initial value is GL_LESS.

glDepthRange(), glEnable(), glPolygonOffset()

       ┌─────────────┬───────────────────────────────────────────────────────────────────────┐
       │             │                OpenGLVersion                                         │
       ├─────────────┼─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┤
       │ Function    │ 2.0 │ 2.1 │ 3.0 │ 3.1 │ 3.2 │ 3.3 │ 4.0 │ 4.1 │ 4.2 │ 4.3 │ 4.4 │ 4.5 │
       │ /           │     │     │     │     │     │     │     │     │     │     │     │     │
       │ Feature     │     │     │     │     │     │     │     │     │     │     │     │     │
       │ Name        │     │     │     │     │     │     │     │     │     │     │     │     │
       ├─────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
       │ glDepthFunc │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │  ✔  │
       └─────────────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┘