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Index › Programming Questions & Help › OpenGL and 3D Libraries › render vertex array to offscreen using glgraphics
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render vertex array to offscreen using glgraphics (Read 1076 times)
serik
render vertex array to offscreen using glgraphics
Sep 15th, 2009, 3:04pm  
Hej,

I try to render a particle system with a vertex array offscreen. I use glgraphics:

Code:
off = new GLGraphicsOffScreen(this, 800, 600, true, 4);


And then somewhere else in the code my particle renderer:

Code:

    PGraphicsOpenGL pgl = (PGraphicsOpenGL) g;
    GL gl = pgl.beginGL(); 
    gl.glEnable( GL.GL_BLEND );
    gl.glBlendFunc(GL.GL_ONE, GL.GL_ONE);
    gl.glEnable(GL.GL_POINT_SMOOTH);
    gl.glPointSize(esize);

    gl.glEnableClientState(GL.GL_VERTEX_ARRAY);
    gl.glVertexPointer(3, GL.GL_FLOAT, 0, posarray);
    gl.glEnableClientState(GL.GL_COLOR_ARRAY);
    gl.glColorPointer(3, GL.GL_FLOAT, 0, colarray);

    gl.glDrawArrays(GL.GL_POINTS, 0, pmax);
    gl.glDisable(GL.GL_BLEND);
    pgl.endGL();


I tried some ideas ... but I do not have enough insights to make this right.

I started to add "off.beginDraw();" and "off." before some lines but it would not work. Then I tried something like this, because I figured that GLGraphicsOffScreen could be a PGraphicsOpenGL:
Code:
    PGraphicsOpenGL pgl = (PGraphicsOpenGL) off;


But that was not working either. It was just rendering to the screen directly.

Any ideas?

Thanks.
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ac
Re: render vertex array to offscreen using glgraphics
Reply #1 - Oct 8th, 2009, 3:10pm  
mmm, GLGraphicsOffscreen is not designed to work with openGL calls. One option would be to create a GLModel object, put your particle system in it and then render the GLModel to the offscreen surface. Something like this:

glg1.beginDraw();
   cam.feed();
   cam.clear(0);    
   model.render();
   cam.done();  
 glg1.endDraw();  

The GLModel object is a recent addition to GLGraphics. In terms of performance, it is very fast because uses VBO's internally to store the vertices. The latest package includes some examples. I hope this answer is still useful.
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