[En beskrivende titel]: glBlendFunc

void glBlendFunc(
  GLenum sfactor, 
  GLenum dfactor 
);


sfactor
Specifies how the red, green, blue, and alpha source-blending factors are computed. Nine symbolic constants are accepted: GL_ZERO, GL_ONE, GL_DST_COLOR, GL_ONE_MINUS_DST_COLOR, GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_DST_ALPHA, GL_ONE_MINUS_DST_ALPHA, and GL_SRC_ALPHA_SATURATE.

dfactor
Specifies how the red, green, blue, and alpha destination-blending factors are computed. Eight symbolic constants are accepted: GL_ZERO, GL_ONE, GL_SRC_COLOR, GL_ONE_MINUS_SRC_COLOR, GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_DST_ALPHA, and GL_ONE_MINUS_DST_ALPHA.

Examples
Transparency is best implemented using glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA) with primitives sorted from farthest to nearest. Note that this transparency calculation does not require the presence of alpha bitplanes in the frame buffer.

You can also use glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA) for rendering antialiased points and lines in arbitrary order.

To optimize polygon antialiasing, use glBlendFunc(GL_SRC_ALPHA_SATURATE, GL_ONE) with polygons sorted from nearest to farthest. (See the GL_POLYGON_SMOOTH argument in glEnable for information on polygon antialiasing.) Destination alpha bitplanes, which must be present for this blend function to operate correctly, store the accumulated coverage.


Jeg må indrømme at jeg ikke er kommet så langt i OpenGL at jeg har forstået blending. Men copy/paste fra manualen kan jeg da finde ud af..
:-)

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