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Some OpenGL alpha-blending problems

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#1 Bong   Members   

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Posted 24 August 2001 - 05:42 PM

I''m currently working on a 2d tile engine for OpenGL, and I''ve got two little problems... 1. Whenever I use alpha-blending with textured quads, the texture is ALWAYS at least half transparent. When I disable alpha-blending, it displays normally, but I can''t get it to display alpha-blended quads at full opaqity, even with glColor4f(1,1,1,1); 2. When I load 32bit textures from TGA files, some green colors are distorted and less detailed. I have a Voodoo 3 GFX card, by the way, it that helps any. Thanks for reading this, let me know if have a solution. - Bong, James Bong

#2 Null and Void   Members   

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Posted 24 August 2001 - 06:26 PM

Are you sure the TGA''s alpha channel is actually opaque? If you''re blending while using it as a RGBA texture.

I''m not sure about your specific case, but some Voodoo cards don''t like 32bit too much. I don''t know what situations exactly though, since I never personally owned a Voodoo.

Do any other programs have either of these problems.

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#3 wolfman8k   Members   

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Posted 25 August 2001 - 04:00 AM

1. You''re using the wrong blending function. To achieve translucent affects you should call this at the beginning of your program:


glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);


2. Try using a higher depth for the internal texture format.




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