Stereo issues with high number of vertices


I’m working on an OpenGL point cloud renderer for big vertex sets and on our target platform I ran into problems I cannot explain.

I implemented a Level of Detail algorithm, segmenting a point cloud via octree and creating a vertex array for each node. Since the density in the data is varying a lot, some nodes have more than 2 million vertices still, most have far less, more like 200k. Now, I’m rendering about 100 vertex arrays (GL_POINTS), via GL_ARRAY_BUFFER. I enabled GL_PROGRAM_POINT_SIZE, to control my point size in the vertex shader dynamically, with respect to LOD level and viewer distance.

Now I have a very weird flickering in stereo mode. (I’m using freeglut to initialize my window with GLUT_STEREO flag set and in my display callback I simply draw into GL_BACK_LEFT and GL_BACK_RIGHT with different projection matrices passed to the shader respectively.) It seems like for some frames not all vertex arrays are drawn. I don’t know what can cause this, it just looks like the frame is not completely drawn, there are definitely octants missing in my octree. Sometimes it even seems like they are not missing but even shifted a bit, as if they get transformed incorrectly. This happens frequently, about twice a second on both left and right frames [1]. Since in mono mode everything is perfectly fine, and everything is single-threaded, I think I can eliminate any problems with my LOD implementation. Also, the LOD part is well tested. After some time (pretty much randomly) it works again, mostly when I logout/login, until, after some time the glitch returns. Also, I get driver crashes sometimes, with Error 3 or 8 returned.

Our setup is a powerwall with a resolution of 6936 x 4096, therefore we have four 4k projectors and we’re using mosaic mode with edge blending. We are running 4 Quadro M6000 on one machine, connected by Quadro Sync. Driver is version 348.27 on Windows 8.1, but I had this problem with all versions I tested so far.

Any ideas what could be the cause of this effect? I realy ran out of ideas. Any hints would be highly appreciated.



Hi Rolond,

Its has been a while since your post. I am curious if you were able to solve your problem. The dropbox link is not working anymore so I couldn’t see your issue. I am having similar issues. I am simulated a large size particle system. I noticed lower half my screen is not updating correctly and causing flickers. I suspect that it is how the left and right buffer draw calls are made.

Will it be possible for you to share you insight? I am also curious what were you glFrustum and lookat setup values for left and right cameras for the large size projection system that you are using? Thank you.

Im having a similar problem, when visualizing many vertexes as particles with GL_VERTEX_PROGRAM_POINT_SIZE and DrawArrays it works perfectly in normal mode, but particles dissapear in Stereo, funny thing is that all the other meshes and lines render perfectly in Stereo.