View Full Version : DisplayLists LARGER than video RAM ... Problem ???

02-21-2009, 03:38 PM
DisplayLists LARGER than video RAM ... Problem ???

Good idea, bad idea ???

I'm wondering what approaches OpenGL apps can take when trying to send more polygons that would fint in VIDEO ram ... into a single rendered Frame of video (Think pre-render ... not realtime render).

02-21-2009, 07:40 PM
In theory because OpenGL is a client / server system the implementation should deal with it, and hopefully cache to RAM and finally the HD according to normal Virtual Memory rules... But there will be a lot of wailing and gnashing of teeth I am sure!!

This is effectively what it does when anything is too big for the GPUs VRAM. It caches to client RAM. Whether this will break with display lists is anyones guess. You may get different mileage from driver to driver implementations. I would not advise it. Having never tried it, I have to say I don't know for sure.. It may just simply not work and break totally.

Also, what you are doing is not going to give good results, and completely defies what display lists are intended for. They are in fact for fast GPU based drawing instructions, not for scripting, which is what it sounds like you are kind of doing.

Also display lists are deprecated in GL3.0 so if this is a long term project then perhaps look at other things like streaming data to Buffer Objects from HD etc.

02-22-2009, 04:57 AM
Overcommitting GPU memory is generally a bad idea. Depending on the driver, your performance will drop considerably.

Some benchmarks:

http://www.equalizergraphics.com/documentation/performance.html#cluster (513^3 data set)

02-22-2009, 03:09 PM
I'm actually just musing ... trying to guess at what kinds of problems might be occuring on my system when I use

3DCOAT to sculpt characters with tons of defination. It's a VOXEL sculptor so you might imagine it opens up a real can or worms when pushed to the limit.

The program crashes and generates nifty web-page error reports to send home to the developer.

I'm looking for any extra tools I might use to try and devine what is really happening when I have 10 million, then 20 million polygons (VOXELS CONVERTED to polys for display).

I'm not writing any code for this software ... just trying to figure out if tossing a new GRAPHICS CARD at it as well as more RAM will make things any better.

New hardware won't make things any better if the problem is not really with poor degradation as polycount goes up.