Point Sprite particles

User Code & Projects
1

jME currently renders particles using either triangles or points, but it’s possible to render point particles that look identical to normal particles using a new OpenGL 2.0 extension called ARBPointSprite and an older extension called ARBPointParameters.









To try this out, add this code to the end of simpleInitGame in TestPointParticles:


// point sprites are useless without a texture
TextureState ts = display.getRenderer().createTextureState();
        ts.setTexture(
            TextureManager.loadTexture(
            TestPointParticles.class.getClassLoader().getResource(
            "jmetest/data/texture/flaresmall.jpg"),
            Texture.MM_LINEAR_LINEAR,
            Texture.FM_LINEAR));
        ts.setEnabled(true);
        pPoints.setRenderState(ts);
       
        // enable point sprite mode, generate special texture coordinates for points
        GL11.glEnable(ARBPointSprite.GL_POINT_SPRITE_ARB);
        GL11.glTexEnvi(ARBPointSprite.GL_POINT_SPRITE_ARB, ARBPointSprite.GL_COORD_REPLACE_ARB, 1);
       
        // set up the distance attenuation
        FloatBuffer ceoff = BufferUtils.createFloatBuffer(0.0f, 0.00001f, 0.0f, 0.0f);
        ceoff.rewind();
        ARBPointParameters.glPointParameterARB(ARBPointParameters.GL_POINT_DISTANCE_ATTENUATION_ARB, ceoff);

2

delicious  :-o

3

How does performance compare?  Do you feel this is something that could be setup (for performance gains) as part of the particle system as an auto-enable on supporting platforms?

4

Beautiful!  This is why I read the forums.  I want this feature, and didn't know how there was a OpenGL feature to do it.  I am doing the distance fadeoff for particles by myself right now.  I'd love to move that out of my code's responsibility.



Plus this gives me a better formula to do the fadeoff if this isn't implemented.

5
How does performance compare?  Do you feel this is something that could be setup (for performance gains) as part of the particle system as an auto-enable on supporting platforms?

I didn't do any specific benchmarks or anything like that, I don't even understand how point rendering works..
I assume that a lot less data needs to be sent to the GPU, which saves bandwidth and memory on the video card.
6

Points are faster than quads for particles on both CPU and GPU.

CPU: there is no need to reorient the particles to face the camera.

GPU: less data to process.



Ideally this would be the default particle implementation with quads as a fall-back for the older hardware.

7

Thanks Lex, that makes good sense.