Re: [Algorithms] planetary chunked LOD terrain

[Sean B. <sp...@ri...>]

Pics on the page look interesting.  Although I must admit I don't see how it
can work.

Here is my question:

In a typical terrain LOD system you start off with a few base right
isosceles triangles.  Each triangle has an associated error, which is,
minimally, abs( (height(leftCorner) + height(rightCorner)) / 2 -
height(midpoint) ).  So if the actual height of the terrain at the
triangle's midpoint (center of the hypotenuse) much deviates from the
average of the heights at the ends of the hypotenuse, you split the triangle
into two smaller triangles and repeat the test.  Now this only works if you
can guarantee that the error of each triangle is greater than the maximum
error of each of its child triangles, so you first perform a bottom-up
preprocessing phase to propagate the triangle errors up from children to
parents, and store on disk the max of each triangle's error and the max of
all of its children's errors.  So if you are fed the terrain values at
runtime with a procedural terrain-generating routine and perform a top-down
refinement, how do you manage without a file of bottom-up propagated error
terms?  Maybe the answer suggests it self with a bit of thought, but I
figured I'd pick your brain first. :)

Oh yeah - and Rescue on Fractalus rules.  I fondly remember, as a wee lad,
stranding men on that hellish wasteland and laughing maniacally while
watching them wave their hands in anxious appeals for mercy.

.sean

----- Original Message -----
From: "Rob James" <poc...@nt...>
To: <gda...@li...>
Sent: Thursday, December 05, 2002 12:47 PM
Subject: Re: [Algorithms] planetary chunked LOD terrain


> Very nice :)
>
> Have you tried generating the geometry procedurally (on the fly) ?
>
> Have a look at http://www.baddoggames.com/planet - (banging own drum)  all
> done with no data set (apart from a ground detail texture).
>
> I used a ROAM-ish algorithm but have also been moving to chunked LOD for
> performance.
>
> I'll add you to my links if I may.
>
> Rob J.
>
>
> > Message: 8
> > From: "Sean Baxter" <sp...@ri...>
> > To: <gda...@li...>
> > Date: Wed, 4 Dec 2002 15:41:08 -0800
> > Subject: [Algorithms] planetary chunked LOD terrain
> > Reply-To: gda...@li...
> >
> > This is a multi-part message in MIME format.
> >
> > ------=_NextPart_000_0340_01C29BAB.90738D40
> > Content-Type: text/plain;
> > charset="iso-8859-1"
> > Content-Transfer-Encoding: quoted-printable
> >
> > I wrote code for planetary chunked LOD terrain.  Pictures are here:
> > http://spec.winprog.org/
> >
>
>
>
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