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Cybertron

Alpha Channel in 16-bit mode?

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Cybertron    122
Is it possible to have a 16-bit texture with an 8-bit alpha channel?? I noticed while looking at the pixel format structure that you can have a surface with alpha-only data. Is it possible to have these 2 surfaces represent a bitmap with an alpha channel?

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Psybr    122
if you are talking about directx surfaces, there is no predefined type. ive only heard of a4r4g4b4, and a1r5g5b5. theres a unknown 16-bit format, but i think its only used for depth buffers.

sorry, i see what ur talking about. if you use two surfaces, its possible, but all the total 24-bit formats have 8 bits per color channel, and none for alpha. i would suggest using 16-bit with alpha, or 32-bit. (if youll notice, most games have 16/32 support, but not 24)

[edited by - psybr on May 5, 2002 7:12:12 PM]

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S1CA    1418
Yes you can *if the hardware you''re running on supports that format* - however it''s not always so desirable since you burn an extra texture stage so you limit what you can do on older chips like the GeForce 1&2, Voodoo2 etc.

If you need the full 8bits of alpha precision (rather than say the 4 in the 4444 format), why not simply use a 32bit texture ?(you can still use 32bit textures with a 16bit backbuffer!)


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Simon O''Connor
Creative Asylum Ltd
www.creative-asylum.com

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