glClear - clear buffers to preset values
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 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(3G), glClearColor(3G), glClearDepth(3G), glClearIndex(3G), glClearStencil(3G), glColorMask(3G), glDepthMask(3G),
glDrawBuffer(3G), glScissor(3G), glStencilMask(3G)