Anybody who knows OpenGL will know this...

(This is not what I am trying to do, but it is a simple explanation of my problem...)

Suppose I have drawn a round ball in MSPaint, with the ball white and the surrounding image black. How can I texture map it to a quad without the black coming up (ie, the surrounding area is see-through, as if the quad was in fact circular)? OpenGL doesn't seem to do it automatically, and the red book doesn't explain how to do it.
Do I have to store alpha-values in the picture? Is there a special blend function?

Thanks,

me.

http://nehe.gamedev.net/ ?...

Thianks, but I'd already downloaded his suite, and he does use this technique, whatever it's called, in tutorial 33, but doesn't explain it. However, I might look through his blending one again if it hints at what I should do.

Thanks,

me.

The Blending tutorial blends the whole texture, not specific colours.

Any other suggestions?

I think article 33 uses the alpha values in the TGA file, but I have tried PSP6, 7 and PS5 but I couldn't find how to write the alpha values to the file :(

PNG files can store 32-bit colour (8 red, 8 green, 8 blue, 8 alpha) so you may want to look into that.

Mhhh......that's right.........if you can load TGA's, you can also load PNG's (that is, if you know the file format..........well, lucky me, I do have code for that :D)

Going to try that some time...