Re: [Algorithms] Terrain performance comparisons

[Adam P. C. <ac...@st...>]

On Tue, 29 Jul 2003, Trent Polack wrote:

> When you say CLOD may be "useless" due to the amazing amount of
> triangles a card can push per second, just think about WHERE a CLOD
> engine puts all those triangles.

Ultimately, LOD (even in "dumb" forms) is necessary just to help the
asymptotics of terrain rendering.  Frustum culling, etc. help get the
drawing time chopped down by a constant factor from the 'n^2' triangles;
then again, as your viewable distance increases, the number of triangles
grows very quickly, especially if you have a wide view angle.  LOD helps
get this down to something more like linear growth with viewable distance
-- which is a -huge- difference if your game has 2-5 mile visibility and
details (procedural or otherwise) on the order of a few meters.  New
hardware will fix constant factors quickly;  you'll have to wait much
longer to fix n^2 growth;  even better, a nice CLOD algorithm can scale
with hardware -- fast users get lots of detail, slow users still get good
detail, but can trade it for visibility.  Not everyone can afford a
GeforceFX to play an online MMORPG (heh, they probably spent it on the
subscription!)

> That said, sometimes an uber-kickass CLOD algorithm just is NOT needed for
> some games. As Charles mentioned, Asheron's Call 2 could have a much better
> terrain engine, but it's still playable, and pretty,

America's Army doesn't do any LOD at all on the terrain and does extremely
well -- but the fog plane is also very close (which apparently gives
certain Radeon owners an advantage *evil glare*) and the levels are very
small.  Even then, my GF4 (admittedly not the demon it once was) bogs down
when lots of terrain is on the screen -- it even outweighs the characters!
:| In theory and practice, it's a tradeoff, but not such an obvious one.

Regards,
Adam C.

> ----- Original Message -----
> From: "Lucas Ackerman" <ack...@ll...>
> To: <gda...@li...>
> Sent: Tuesday, July 29, 2003 5:25 PM
> Subject: Re: [Algorithms] Terrain performance comparrisons
>
>
> > Jonathan Blow wrote:
> >
> > >Let's look at this in a slightly different way: most graphics LOD
> algorithms
> > >are focused on decreasing the number of triangles/sec needed to display
> > >the scene.  But triangles/sec is the single most abundant,
> > >uncontended-for resource in all of game development.  So WTF are
> > >we putting all this energy there?
> > >
> > >
> > >
> > LOD is not about quantity, it's about quality.  Quantity can increase
> > with hardware speed and software efficiency, but quality improves by
> > increasing the intellignece with which you allocate your limited
> > quantity.  If triangles/sec were the fundamental measure of game
> > quality, LOD would be pointless.
> >
> > Decreasing the quantity of triangles required to display part of a scene
> > without decreasing the quality is only half of the equation.  The other
> > half is to increase the quantity used to display the parts of the scene
> > that will contribute most to the quality.
> >
> > It is also possible, of course, to use the flexibility in quality as a
> > means to put more stuff in a given scene, or to look at a scene in ways
> > you couldn't before.
> >
> > The reason a lot of time and energy goes into LOD is that it's not an
> > easy problem to solve all aspects of in a way that satisfies all people.
> >
> > -Lucas
> >
> >
> >
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