glClear function

Article
12/11/2020

The glClear function clears buffers to preset values.

Syntax

void WINAPI glClear(
   GLbitfield mask
);

Parameters

mask

Bitwise OR operators of masks that indicate the buffers to be cleared. The four masks are as follows.

Value	Meaning
GL_COLOR_BUFFER_BIT	The buffers currently enabled for color writing.
GL_DEPTH_BUFFER_BIT	The depth buffer.
GL_ACCUM_BUFFER_BIT	The accumulation buffer.
GL_STENCIL_BUFFER_BIT	The stencil buffer.

Return value

This function does not return a value.

Error codes

The following error codes can be retrieved by the glGetError function.

Name	Meaning
GL_INVALID_VALUE	Any bit other than the four defined bits was set in mask.
GL_INVALID_OPERATION	The function was called between a call to glBegin and the corresponding call to glEnd.

Remarks

The glClear function sets the bitplane area of the window to values previously selected by glClearColor, glClearIndex, glClearDepth, glClearStencil, and glClearAccum. You can clear multiple color buffers 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. The glClear function ignores the alpha function, blend function, logical operation, stenciling, texture mapping, and z-buffering.

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

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

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

The following functions retrieve information related to glClear:

glGet with argument GL_ACCUM_CLEAR_VALUE

glGet with argument GL_DEPTH_CLEAR_VALUE

glGet with argument GL_INDEX_CLEAR_VALUE

glGet with argument GL_COLOR_CLEAR_VALUE

glGet with argument GL_STENCIL_CLEAR_VALUE

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Header	Gl.h
Library	Opengl32.lib
DLL	Opengl32.dll