PDA

View Full Version : Blend Shadow



piazzesi
11-08-2002, 03:12 PM
Hello.
I am blending with 32 bit bmp ( http://www.geocities.com/mariopgv/sombra.bmp ) as well as with monochrome primitive, and in both cases i get a dark shadow in some angles, in the image linked above i used,
GL_DST_COLOR, GL_DST_ALPHA. does anyone know how to work around this?

[This message has been edited by piazzesi (edited 11-08-2002).]

[This message has been edited by piazzesi (edited 12-05-2003).]

dorbie
11-08-2002, 04:50 PM
This could be the alpha in the BMP not being set to zero around the leaf but the blendfunction you supply is strange and may be your problem.

You claim you have source color multiplied by destination color, and destination color is multiplied by destination alpha.

Try a glBlendfunc(SRC_ALPHA, ONE_MINUS_SRC_ALPHA);

If you still have problems or don't want to do this for some exotic rendering reason you haven't explained then use glAlphaFunc to eliminate the fragments that aren't well behaved.

dorbie
11-08-2002, 04:57 PM
You'll also need to glEnable(GL_ALPHA_TEST) if you want to use glAlphaFunc.

piazzesi
11-09-2002, 09:34 AM
Thanks for your reply, y tried
GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, and it completely fades the texture, i played with DST and SRC, and got different unwanted effects, as for glAlphaFunc, it does no difference, seems that the color around the leaf is alpha transparent.

piazzesi
11-09-2002, 10:01 AM
Looks like its solved, i added a glColor4f(1,1,1,0) to the leaf triangles and the shadow is gone. Thanks.