Re: [Flightgear-devel] Outerra

[Tim M. <tim...@gm...>]

On Wed, Feb 10, 2010 at 10:55 AM, James Sleeman <fli...@go...>wrote:

> On 10/02/10 22:25, Martin Spott wrote:
> > Dense forests are possible by tweaking the 'tree-density' parameter in
> >
> Really?  Dense like was shown in that video?  Without requiring a
> cluster of supercomputers to run it at a workable framerate?
>
> Probably not. Outerra uses procedural terrain, and thus has a built in
level-of-detail system at a fine scale; therefore they are able to control
the polygon count for a given tree density and distance. Our terrain tiles
are big, and there's no terrain LOD. We've fooled with various LOD
approaches for trees, but so far none are very satisfying. They also have a
clever way of doing the tree placement on the GPU and keeping the position
and texture coordinates there, which speeds up the tree rendering.

 > chance of getting even better textures than we currently have  :-)
> >
>
> As much as new textures are desirable, getting results like Outerra is
> more than that, in fact I'd say the textures are a very small part.
>
>  http://outerra.blogspot.com/2009/05/horizontal-displacement.html
>
> Quick version, image down the page, left & right are the same textures,
> the right side has a horizontal displacement using a fractal source and
> lots of math I don't have a hope of understanding in my lifetime to make
> the complex "rockyness".  Same textures, left looks not so different to
> flightgear, right looks holy-crap-thats-awesome.
>

There's no question that Outerra is a rich source of terrain envy and
inspiration. You should also keep in mind our objectives and theirs. Every
terrain detail below 76mX76m is procedurally generated, although they do
have a story for linear features like roads. In a flight simulator our
ultimate objective should be for the scenery to be usable for VFR training.
This is a high bar. I think that implies that we want "ground truth" on a
finer scale than Outerra's, but we also don't care about meter-and-less
terrain detail, except around airports. Perhaps helicopter simulation has
different requirements. Also, Outerra has hardware requirements that will
leave a lot of our users in the dust. We're leaving a lot of our users in
the dust too with shaders and all, but I think we have enough configuration
parameters available to still permit them to run fg.

Outerra still has a long way to go to meet their goals, but it's fun to
watch their progress.

Tim