Jitter / Perf issue

    jeffd's icon
    jeffd
    Feb 19 2014 | 10:46 am
    Hi I am new to this community and a beginner with Jitter. I have a very straightforward issue which I am sure someone can help me with. I need to display in a CPU-effective way a 3D object which is just a cloud of numerous (possibly > 500k) points. I don't care about building volumes, surfaces, textures. Just the plain cloud of points. By display, I mean, obviously, zoom into, rotate, translate. The kind of stuff jit.gl.render can do. Help !
    • Feb 19 2014 | 11:11 am
      dtr's icon
      dtr
      Well you already said it, the stuff jit.gl.render can do. Use jit.gl.mesh and send it a matrix containing the positions of your points.
      How many points you'll be able to visualize at a decent framerate depends on your hardware.
      There's 1 caveat that might or might not affect you. Points have no volume. They get drawn according to the point_size attribute you set on the jit.gl.mesh. This means that a point close by and far away have the same size. If you need them to look larger/smaller depending on how far they are you have to give them a volume. You might wanna use jit.gl.multiple then. Maybe there other tricks for that, not sure.
    • Feb 19 2014 | 2:19 pm
      jeffd's icon
      jeffd
      it works perfectly ! thx !!
    • Mar 29 2014 | 7:54 pm
      jeffd's icon
      jeffd
      Now I have another performance issue. I would like my cloud of 1 million points (X,Y,Z) to be colored according to a very simple formula R=G=f(X^2+Y^2,a), B=255 where the parameter "a" changes at each frame but has a limited number N of values.
      Basically the closer a point is to the Z-axis, the bluer ; the further, the whiter. But with the parameter "a", I can introduce a pulse in the colur of the cloud.
      Calculating at each frame a matrix of coulors and giving it to my jit.gl.mesh object takes too long.
      Any idea of how to make this more efficient ? Use the capabilities of my GPU in this regard too ?
      I could precalculate N 3D-images that are Z-cylinders of color going from blue to white, but then what ? How can I "mix" the images to render the cloud of points with the right color ?
      Thx for your help