HP Workstation zx2000 OpenGL 1.1 Reference for HP-UX 11.x - Page 100

D glDepthFunc glDepthFunc glDepthFunc: specify the value used for depth buffer comparisons. C Specification void glDepthFunc( GLenum func) Parameters 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. Description 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. 100 Chapter 4