I'm currently working on a small particle engine. I have to billboard the particles, so I gotta get them perpendicular to the camera. How do I best do that?
When the particle rendering procedure is called, the camera is already translated and rotated. I know the coordinated and the rotation matrix of the camera. How can I get the particles perpendicular?
If you use OpenGL then you can use GL_Point_Sprite_ARB extension which does all work for you. Take a look at this sample.
I don't think that's a good idea. Without that I have FPS at 60, with that extension I have FPS of 3.
Alright, I got it running with that. One problem: How can I do the blending stuff? I mean, my particles should be rendered additive or subtractive, but the background should never shine through.
How about glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA)?
Hmm I get the feeling that my site is not as visible as it should be..
I've written a tutorial on how to get billboard sprites in OpenGL.
Get it here: http://www.nitrogen.za.org/viewtutorial.asp?id=12
Billboarding works fine now, thank you. I think I would have never figured that out without your help.
But, blending still doesn't work as it's supposed to. I have about 10 quads overlapping each other and I want them to be blended additively, but I don't want the background to shine through. I got the same problem with subtractive blending.
Seems to be the order in which you draw things... if you don't want to shine things through, draw in reversed order, saying from camera to the back.
<a href="http://www.greatgamesexperiment.com/game/Valgard/?utm_source=gge&utm_medium=badge_game"><img border="0" alt="GGE" title="GGE" src="http://static.greatgamesexperiment.com/badge/game/valgard/gge400x56.png"></a>
I'm drawing the background first, then the particles. Doing it the other way round, all particles are black.
I can imagine 2 reasons why the particles are black:
- you multiply the colors (multiply with black is black)
- you disable zbuffer when rendering the particles... then the background will be drawn "over" the particles.
hmmm... I don't really know what kind of effect you want to achieve... any chance you post a screenshot and explain it a bit clearer?
<a href="http://www.greatgamesexperiment.com/game/Valgard/?utm_source=gge&utm_medium=badge_game"><img border="0" alt="GGE" title="GGE" src="http://static.greatgamesexperiment.com/badge/game/valgard/gge400x56.png"></a>
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