glDepthFunc Subroutine

OpenGL 1.1 for AIX: Reference Manual

glDepthFunc Subroutine

Purpose

Specifies the function used for depth buffer comparisons.

Library

OpenGL C bindings library: libGL.a

C Syntax

void glDepthFunc(GLenum function)

Parameters

function

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 default function is GL_LESS.

Description

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

The function parameter 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 z value is less than the stored z value.
GL_EQUAL	Passes if the incoming z value is equal to the stored z value.
GL_LEQUAL	Passes if the incoming z value is less than or equal to the stored z value.
GL_GREATER	Passes if the incoming z value is greater than the stored z value.
GL_NOTEQUAL	Passes if the incoming z value is not equal to the stored z value.
GL_GEQUAL	Passes if the incoming z value is greater than or equal to the stored z value.
GL_ALWAYS	Always passes.

The default value of function is GL_LESS. Initially, depth testing is disabled.

Errors

GL_INVALID_ENUM	function is not an accepted value.
GL_INVALID_OPERATION	The glDepthFunc subroutine is called between a call to glBegin and the corresponding call to glEnd.

Associated Gets

Associated gets for the glDepthFunc subroutine are as follows. (See the glGet subroutine for more information.)

glGet with argument GL_DEPTH_FUNC

glIsEnabled with argument GL_DEPTH_TEST.

Files

/usr/include/GL/gl.h

Contains C language constants, variable type definitions, and ANSI function prototypes for OpenGL.

Related Information

The glBegin or glEnd subroutine, glDepthRange subroutine, glEnable or glDisable subroutine, glPolygonOffset subroutine, glPolygonOffsetEXT subroutine.

OpenGL Overview.