qb64/internal/help/_glClear.txt

'''_glClear:''' clear buffers to preset values


{{PageSyntax}}

:: [[SUB]] _glClear ([[BYVAL]] mask AS [[_UNSIGNED]] [[LONG]])
::  void '''_glClear'''(GLbitfield {{Parameter|mask}});


{{Parameters}}
* ''mask'' that indicate the buffer [[OR]] buffers to be cleared. The three masks are [[_GL_COLOR_BUFFER_BIT]], [[_GL_DEPTH_BUFFER_BIT]], and [[_GL_STENCIL_BUFFER_BIT]].


{{PageDescription}}

* [[_glClear]] sets the bitplane area of the window to values previously selected by [[_glClearColor]], [[glClearDepth]], and [[_glClearStencil]]. 
* 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 depth-buffering are ignored by [[_glClear]].

* [[_glClear]] takes a single argument that is the bitwise OR of several values indicating which buffer is to be cleared. The values are as follows:

::: [[_GL_COLOR_BUFFER_BIT]]: Indicates the buffers currently enabled for color writing.
::: [[_GL_DEPTH_BUFFER_BIT]]: Indicates the depth 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.


{{PageNotes}}

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


{{PageErrors}}

{{KW|_GL_INVALID_VALUE}} is generated if any bit other than the three defined bits is set in {{Parameter|mask}}.


{{PageUseWith}}

{{KW|_glGet}} with argument {{KW|_GL_DEPTH_CLEAR_VALUE}}

{{KW|_glGet}} with argument {{KW|_GL_COLOR_CLEAR_VALUE}}

{{KW|_glGet}} with argument {{KW|_GL_STENCIL_CLEAR_VALUE}}


{{PageSeeAlso}}
* [[_GL]] 
* [[_glClearBuffer]], [[_glClearColor]], [[_glClearDepth]], [[_glClearStencil]] 
* [[_glColorMask]], [[_glDepthMask]], [[_glStencilMask]]
* [[_glDrawBuffer]], [[_glDrawBuffers]]
* [[_glScissor]]


{{PageCopyright}}