glClear - clear buffers to preset values

glClear
	glClear(mask) -> None

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.

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	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_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.

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

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

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

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

glClearAccum,	glClearColor, glClearDepth, glClearIndex,
glClearStencil, glDrawBuffer,	glScissor