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Multiplying Alphas thru Multitexture

Started by alphablend Jan 22, 2003 at 9:29 PM 2 replies 200+ views

Original Post

Jan 22, 2003 at 9:29 PM

I was wondering how I could do this: i have one texture in the first with an alpha channel i have another texture (no alpha channel) that I want to multiply against the other textures alpha channel only, thereby having an end texture with no rgb change only alpha. anyone know, or where i might look? Thanks!

alphablend

Jan 22, 2003 at 9:33 PM

btw, what would be an easy way of adding an alpha channel to a rgb texture in memory...

thanks again

zedzeek

Jan 22, 2003 at 10:32 PM

i didnt understand the first part fully but check out the combine extension (part of opengl 1.3)

for the second q, u cant u will have to create another RGBA texture + copy the RGB data in from the first texture

http://uk.geocities.com/sloppyturds/kea/kea.html
http://uk.geocities.com/sloppyturds/gotterdammerung.html

Nypyren

Jan 22, 2003 at 11:03 PM

If you multiplied the first texture by pure white second texture, the RGB should stay the same as the first, right?

I''m used to D3D, so I don''t know if there is a difference.

For textures, use 32-bit. Each 8 bits is a channel (Blue, Green, Red, Alpha)

If you load a texture off of disk, you can use formats like .tga and .png which include the alpha channel in the file.

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