View Full Version : Blending clouds and sun
I have a bitmap containing clouds (blue background with white clouds) and a sun (black background with white sun). How can I blend these to give the effect of the clouds going over the sun but the sun coming out when it goes over the clouds' blue background?
05-30-2002, 01:02 AM
okay, if u just have a sky plane... it's pretty easy
draw two quads on the "ceiling":
farther one will have the sun texture mapped onto it blackpixels => alpha=0 there else alpha=1
closer quad: map the cloud texture to it, alpha=(red+green intensity)/2.0
//this'll make the blue pixels have alpha=0, and white pixels alpha=1 etc http://www.opengl.org/discussion_boards/ubb/smile.gif
and u should be done
won't be the best looking, but u should be done
if u want to learn about good cloud stuff http://www.gamedev.net/community/forums/topic.asp?topic_id=86024
btw, i don't check this forum often... so if u have a question or something e-mail me.
Thanks a bunch, I will give this a try.
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