Whole Framebuffer Operations - OpenGL ES 2.0 / GLSL 1.0

Fine Control of Buffer Updates [4.2.2]

void ColorMask(boolean r, boolean g, boolean b, boolean a);
void DepthMask(boolean mask);
void StencilMask(uint mask);
void StencilMaskSeparate(enum face, uint mask);
// face: FRONT, BACK, FRONT_AND_BACK
 

Clearing the Buffers [4.2.3]

void Clear(bitfield buf);
// buf: Bitwise OR of COLOR_BUFFER_BIT, DEPTH_BUFFER_BIT, STENCIL_BUFFER_BIT
void ClearColor(clampf r, clampf g, clampf b, clampf a);
void ClearDepthf(clampf d);
void ClearStencil(int s);