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16 Bit Alpha Blending

General and Gameplay Programming Programming

Started by Qoy May 31, 2000 01:04 AM

2 comments, last by Qoy 23 years, 10 months ago

Qoy

127

Author

May 31, 2000 01:04 AM

I'm thinking about trying to implement an alpha blending feature in my game for some menu screen effects, and for fades to various colors. I'm using 16 bit color. I have found plenty of documentation on alpha blending, color addition, subtraction, and numerous equations for color effects, so that's no problem, but going pixel by pixel and applying these effects is just WAY to slow. I've heard before of using color lookup tables to implement these effects in 16 bit, but I haven't been able to find much info on how to do this. Does anyone know where I can find information on doing *fast* alpha blending or other color translucency effects with 16 bit color? By the way.. I would prefer stuff that uses C/C++, because I don't know assembly yet. But if the only way to make it fast is assembly, that'll have to be it. Also, I'd rather not use MMX, because I have some friends who have some old computers

Thanks! Edited by - Qoy on 5/31/00 1:06:08 AM

cyberben

122

May 31, 2000 01:34 AM

Hello there, well to start you''ll have to use assembly to get anywhere with alpha blending as it does take a fair bit of cpu power. It has to be as effiecent as possible. There''s an article here on gamedev.net in the reference area on MMX enhanced alpha blending, which actually also gives examples of a standard alpha blending and a couple of better improvements ending with the fastest one the MMX alpha blending routine. It uses C or C++ w/ inline assembly. With a little research and some mor einline assembly you can use the CPUID instruction to detect the presence of MMX support on a computer to decide which function to use. So it will run on a wide variety of machines.
Hope this helped!
See ya,
Ben

__________________________Mencken's Law:"For every human problem, there is a neat, simple solution; and it's always wrong."
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jenova

122

May 31, 2000 01:38 AM

ok. to recommend anything i would need a little more info. are you developing a DOS based game or Windows 9x/NT? if Windows then are you using DirectX/OpenGL etc? if DOS are you using VESA/MODE X, etc?

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