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Silex

large vbo (100mb) issues

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i'm visualizing large point clouds, and to get reasonable perfomance i'm using arb vertex buffer objects. my problem is that as the size of the vbo's increases, performance seems to decrease exponentially. is this a known issue with vbo's? would splitting them into smaller vbo's help? or am i doing something wrong?

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But VBOs are used to cache geometry data...not your movies!!! [lol]

100MB is too much...I've read in a thread on this forum that there is a lower and upper bound and the optimum is about 8-16 MB (for a single object) but no more!

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well its rendering a 100 mb vbo right now :P just not quite as efficiently as i expected.

maybe i'll try splitting it into several 8 mb vbo's, see if that help...

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As far as I can tell you don't even have to physically split the buffer, it should be enough if you just don't render it all at once (and add some frustum/occlusion culling).
I had a similar problem - one big heightmap with approx. 140 MB of vertices/texcoords/normals within one big buffer.
After doing some trial and error tests I've found out, that I get the best performance when I render 4096 vertices at once via glDrawElements.
I'm not using VBOs though at the moment (just normal indexed vertex buffers), so you might get different results.
Maybe you want to give it a try anyway ;)

Greets

Chris

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How much memory does your gfx card have?

Remember OpenGL server needs some memory to itself on the gfx card...

If your VBO is too large, it will not fit in gfx memory, and thrashing will ensue. Not good for framerates :(

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The card has a lot more than 100mb, so I don't think thrashing is the problem. Also, with the larger VBO's I'm running into some stability issues where the machine will freeze. This could be hardware related (overheating?) or maybe a problem with the linux nvidia drivers im running....

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