Archived

This topic is now archived and is closed to further replies.

Ilici

Blending Factors

Recommended Posts

i want to make some shadows (raycasting on the ground plane). when i draw the shadow triangles with blending and 0.5 alpha, two overlapping triangles will overbrighten the shadow. what blending func shoul i use so the shadow looks nice?

Share this post


Link to post
Share on other sites
Just use the alpha value of that triangle color.

Be sure to enable the alpha channel blending:

glEnable(GL_ALPHA_TEST); // enable alpha testing
glAlphaFunc(GL_GEQUAL, 0.05f); // if alpha < 0.05, don''t draw pixel
glColor4f(0.0f, 0.0f, 0.0f, 0.5f); // black with 50% blending

Share this post


Link to post
Share on other sites
I have a feeling you might be rendering the blended rectangle over the screen more than once, (if you are using a method similar to nehe)

Make sure you draw shadows last, ie.

1. draw everything

2. Enable the start bit of shadows.
3. Do the shadow passes on every object

4. Draw one blended rectange

Hope this answers the question.

Share this post


Link to post
Share on other sites