Passes if the incoming depth value is greater than or equal to the stored depth value.
The initial value of
GL_LESS. Initially, depth testing is disabled.
Even if the depth buffer exists and the depth mask is nonzero, the depth buffer is not updated if the depth test is disabled.
GL_INVALID_ENUM is generated if
func is not an accepted value.
GL_INVALID_OPERATION is generated if
glDepthFunc is executed between the execution of
glBegin and the corresponding execution of
glGet with argument
glIsEnabled with argument
Enable or disable writing into the depth buffer
C Specification ...