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OpenGL 1.1 for AIX: Reference Manual

glClear Subroutine


Clears buffers to preset values.


OpenGL C bindings library: libGL.a

C Syntax

void glClear(GLbitfield Mask)


Mask Bitwise OR of masks that indicate the buffers to be cleared. The four masks are GL_COLOR_BUFFER_BIT, GL_DEPTH_BUFFER_BIT, GL_ACCUM_BUFFER_BIT, and GL_STENCIL_BUFFER_BIT.


The glClear subroutine sets the bit plane area of the viewport to values previously selected by glClearColor, glClearIndex, glClearDepth, glClearStencil and glClearAccum. Multiple color buffers can be cleared simultaneously by selecting more than one buffer at a time using glDrawBuffer.

The pixel ownership test, the scissor test, dithering and the buffer writemasks affect the operation of glClear. The scissor box bounds the cleared region. Alpha function, blend function, logical operation, stenciling, texture mapping, and z-buffering are ignored by glClear.

The glClear subroutine takes a single argument that is the bitwise OR of several values indicating which buffer is to be cleared.

The values are:

GL_COLOR_BUFFER_BIT Indicates the buffers currently enabled for color writing.
GL_DEPTH_BUFFER_BIT Indicates the depth buffer.
GL_ACCUM_BUFFER_BIT Indicates the accumulation buffer.
GL_STENCIL_BUFFER_BIT Indicates the stencil buffer.

The value to which each buffer is cleared depends on the setting of the clear value for that buffer.

glGet with argument GL_COLOR_CLEAR_VALUE

glGet with argument GL_STENCIL_CLEAR_VALUE.


If a buffer is not present, then a glClear directed at that buffer has no effect.


GL_INVALID_VALUE A bit other than the four defined bits is set in Mask.
GL_INVALID_OPERATION The glClear subroutine is called between a call to glBegin and the corresponding call to glEnd.

Associated Gets

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

glGet with argument GL_ACCUM_CLEAR_VALUE

glGet with argument GL_DEPTH_CLEAR_VALUE

glGet with argument GL_INDEX_CLEAR_VALUE


/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, glClearAccum subroutine, glClearColor subroutine, glClearDepth subroutine, glClearIndex subroutine, glClearStencil subroutine, glDrawBuffer subroutine, glScissor subroutine.

OpenGL Overview.

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