View Full Version : Unused alpha channel
04-18-2002, 02:24 PM
Will having an unused alpha chennel in your textures affect speed performance? I know it is a waste of memory.
It won't affect performance, and on many current graphics cards doesn't even hurt memory either. For example, many (all?) nVidia cards store 24-bit RGB textures as 32-bit.
In fact, uploading 32-bit textures to memory can be faster than uploading 24-bit textures, because the driver doesn't need to pad the values for it.
04-18-2002, 05:41 PM
Hmm... you may want to test this theory.
There are also more complex issues, like hosing your quality depending on the chosen internal texture format, often forced by the user.
04-18-2002, 06:32 PM
Thanks for the help.
One thing I did notice was that choosing GL_UNSIGNED_BYTE rather than GL_UNSIGNED_INT_8_8_8_8 speeded things up for me. This was strange to me but I guess it has to do with the acceleration hardware... perhaps the driver was a bit dumb.
04-18-2002, 10:19 PM
Originally posted by Robin Forster:
One thing I did notice was that choosing GL_UNSIGNED_BYTE rather than GL_UNSIGNED_INT_8_8_8_8 speeded things up for me.
Perhaps you should try GL_UNSIGNED_INT_8_8_8_REV instead. http://www.opengl.org/discussion_boards/ubb/wink.gif
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