HP Workstation zx2000 OpenGL 1.1 Reference for HP-UX 11.x - Page 35

B glBlendFunc Examples Blend function (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA) is also useful for rendering anti-aliased points and lines in arbitrary order. Polygon anti-aliasing is optimized using blend function (GL_SRC_ALPHA_SATURATE, GL_ONE) with polygons sorted from nearest to farthest. (See the glEnable, glDisable reference page and the GL_POLYGON_SMOOTH argument for information on polygon anti-aliasing.) Destination alpha bitplanes, which must be present for this blend function to operate correctly, store the accumulated coverage. Notes Incoming (source) alpha is correctly thought of as a material opacity, ranging from 1.0 (KA), representing complete opacity, to 0.0 (0), representing complete transparency. When more than one color buffer is enabled for drawing, the GL performs blending separately for each enabled buffer, using the contents of that buffer for destination color. (See glDrawBuffer.) Blending affects only RGBA rendering. It is ignored by color index renderers. Errors • GL_INVALID_ENUM is generated if either sfactor or dfactor is not an accepted value. • GL_INVALID_OPERATION is generated if glBlendFunc is executed between the execution of glBegin and the corresponding execution of glEnd. Associated Gets glGet with argument GL_BLEND_SRC glGet with argument GL_BLEND_DST glIsEnabled with argument GL_BLEND See Also glAlphaFunc, glClear, glDrawBuffer, glEnable, glLogicOp, glStencilFunc Chapter 2 35