Speed differences for billboarding
Author
OK, I''ve now found 2 ways of doing billboarding. One is to use
blending, the other to use alpha testing as follows :-
glDisable(GL_BLENDING)
glEnable(GL_ALPHA_TEST )
glAlphaFunc(GL_GREATER,0.5)
Of, course, this assumes that your texture has been set-up with
transparent areas having an alpha value < 0.5 ...
My question is which is the best method? Obviously, I have to
switch blending back on for rendering my particle system etc.
However, using the above technique for billboarding means that I don''t have to pass the polygons in depth-first order ..... no sorting for me :-)
Any comments ....
an alpha test is far quicker than doing blending. so if its good enuf use it instead of blending
http://members.xoom.com/myBollux
http://members.xoom.com/myBollux
also to get really picky 
processors tend to do the ''not equal 0'' in one opp
thus glAlphaTest(GL_NOTEQUAL,0.0);
maybe be the quickest of all (i havent tested this though)
http://members.xoom.com/myBollux
processors tend to do the ''not equal 0'' in one opp
thus glAlphaTest(GL_NOTEQUAL,0.0);
maybe be the quickest of all (i havent tested this though)
http://members.xoom.com/myBollux
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