point clouds


    Feb 11 2006 | 11:23 pm
    Greetings,
    Has anyone worked with point clouds in open GL? I tried the brute force method of reading each point into jit.gl.sketch, but it took along time. The results were a tad sluggish averaging 8 to 9 fps on G5 dual 2.7. Is there is a more efficient way of doing this? If not can anyone recommend a plug in or application for the mac that will convert point clouds to obj files? I've seen several on line but the cost is prohibitive enough to preclude experimentation.
    Thanks
    Barney

    • Feb 11 2006 | 11:43 pm
      Well, I learned a new term today. I don't see anyway of efficiently doing this in jitter right now. I think the best way to go would be to modify the jit.gl.gridshape SDK example and change the @position and @scale attributes to matrix inputs for drawing, say, thousands of spheres per frame. You would pass in 2 3-plane nx1 matrices with position and scale data and on each render pass, it would call draw for every scale/position pair, just moving the sphere around.
      wes
    • Feb 13 2006 | 2:03 am
      Thanks Wes, Will the jit.gl.gridshape solution run more efficiently on the graphics card once all the data points are loaded? Barney
    • Feb 13 2006 | 3:23 am
      You know, I'm not incredibly familiar with the point cloud litterature, so I'm going to refrain from answering your question as I don't want to posture a wild guess. That said, the best thing to do is avoid tons of max messages. Point clouds seem like an ideal candidate for their own external as from what cursoiry knowledge I have they require a decently sophisticated data structure to manage their rendering. From what I could tell, people were using octrees to choose the detail of the rendering. If you set this up in a jitter external, you could have a float parameter for precision that would traverse the octree to a particular level of detail. This way, you could adjust the detail to the machine you're running on and get interactive frame-rates.
      Hope this helps. If you're really into the point cloud thing, I would take this opportunity to learn how to make a jitter external. Once you make one successfully, you realize how simple it really is and your jittering will be that much better since you can overcome hacking objects together and instead make your own, saving you much processing power.
      good luck, wes
      PS, on yahoo groups, there is a jitter-dev list. you may find the archives handy when you start out.
    • Feb 14 2006 | 12:55 am
      Wes, Thanks again. Sounds like my summer vacation plans are starting to become a little more concrete. Barney