----- Original Message ----- 
From: "Frederic Bouvier" <[EMAIL PROTECTED]>
To: "FlightGear developers discussions" <[EMAIL PROTECTED]>
Sent: Sunday, October 17, 2004 4:38 AM
Subject: Re: [Flightgear-devel] VBOs - performance test results


> James Turner a écrit :
>
> >
> > 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 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.
>
> You are wrong here as long as FG will use state changes ( read different
> textures ) to represent terrain property ( forrest, crop, urban ). You
> can't put state changes in a VBO, so you end up with multiple, small
> VBOs that is worst than display lists.

Frederic!  I must admit that you are absolutly right with Dlists I got 107
fps and only 78 fps w/ VBO on 5950Ultra
It's w/o shaders. I make additional test And tell results with shaders.


>
> That could be different with another terrain engine that would drape a
> single, large and unique texture on a single tile made with a single
> geometry object.
>
> People arguing for VBOs are always forgetting this reality.
>
> -Fred
>
>
>
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