On 17 Oct 2004, at 10:15, Erik Hofman wrote:
Before other people think "WOW, FG could run 60% faster!!!", please keep in
mind that an application like FG can't do everything just by using VBOs and DLists.
For what it's worth, experts keep telling me the display lists are always faster than VBO's anyhow. The advantage of VBO's comes when you want to use non-static data like morphing.
That and the fact that all drivers seem to support display lists at the moment make me believe we should stick to display lists a little longer.
That sounds totally incorrect as I understand it. VBOs are essentially the same ideas as vertex arrays, but with more control over which memory
^^^^^^^^^^^^^ I assume you mean display lists here? If not, VBO's are vertex arrays.
they are located in (system, AGP or GPU) and with how they will be updated. They can be used for 'streamed' vertex data such as skeletal animation and morphing (by specifying that they should not be GPU resident) but for FG the benefit (which should be large) would come from placing each tile (or other large data set) and mesh onto the GPU as a fixed, resident VBO.
The win comes from avoiding the transfer of static vertex data over the AGP bus each frame, and since flight simulators have almost zero per-frame mesh data (apart from maybe smoke, moving water and clouds) this should give a large win on systems which are bandwidth limited (it won't help the fill-rate limited systems, of course). Also, the drivers should optimise GPU-resident VBOs memory layout, which again will give a substantial win.
This is exactly what display lists do, but they do more (if properly implemented), they optimize the rendering order of the geometry. Display lists generate a static list of OpenGL commands (including geometry data) while VBO's only handle the geometry data.
Given FG's goal of cross-platform support, the obvious (only?) way not to be held back to the original OpenGL 1.1 and 1.2 APIs is using some layer which abstracts this.
I'm not opposed to VBO's, but I don't think they will gain s much as you are hoping for. Besides the fact that they will not get included in plib.
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