hi.

i dont really understand your question, what do you mean by the "firefly effect"? is it the glowy visuals?

if thats the case it is done using additive blend in opengl.
just add this to your code
Code:

import processing.opengl.*;
import javax.media.opengl.GL;

PGraphicsOpenGL pgl;
GL gl;

void setup(){
//just put what you would normaly put here
}

void draw(){
//here you just add this code:
pgl = (PGraphicsOpenGL)g;
gl = pgl.beginGL(); //getting the GL object used by processing
gl.glEnable(GL.GL_BLEND);  // enabling blend
gl.glBlendFunc(GL.GL_SRC_ALPHA, GL.GL_ONE); //defining additive blend
pgl.endGL();

//now everything you draw will be drawn using additive blend
//making glows more glowy! 
}
 

if this is not what you are asking for then i dont know...

Pelintra is correct. You want additive blending on billboards (Quads that always face the camera) with a feathered semi-transparent texture. If you decide you like regular alpha transparency better than additive blending, you'll want to render the transparent sprites from back to front order in relation to the camera. (Transform all sprite positions into camera space and sort based on z value) However if you just stick to additive blending this isn't an issue. Also with additive blending make sure to disable depth tests when rendering so you don't render a close sprite first and have background sprites not render over it.

Unfortunately if you want to have non-transparent objects in the scene you'll still need to sort your billboards from back to front even if you're using additive blending. In that case you render all the non transparent objects first, then you render transparent objects with depth checks on from back to front. This way any transparent objects that fall behind solid objects will not draw but they will still draw over previously drawn transparent objects.

Hope that info helps! Transparency is one of those things that seems easy at first but can really be a pain to do right.

Jack