- clear buffers to preset values



C SPECIFICATION


PARAMETERS

       _param1  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.


DESCRIPTION

       glClear sets the bitplane area of  the  window  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  func-
       tion,  blend function, logical operation, stenciling, tex-
       ture 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   cur-
                                   rently enabled for color writ-
                                   ing.

       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.


NOTES

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


ERRORS

       GL_INVALID_VALUE is generated if any bit  other  than  the
       four defined bits is set in _param1.

       GL_INVALID_OPERATION  is  generated if glClear is executed
       between the execution of  glBegin  and  the  corresponding


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