Still waiting for my key. In the meanwhile, thinking about general geologic features that are pretty universal in nature. If you imagine an arbitrary rugged mountainous texture covering the surface of a planet, that is pretty much what it seems Terragen creates when you generate a surface. In nature, though, erosional forces (mostly water) act on this through time and tend to cut out local low canyons and make them deeper. The material is removed and is deposited in splays that form in the valleys down stream where water velocity slackens. These splays hide the rugged rock formations below and create a surface that is generally much smoother and nearly flat. This is reminiscent of the water table in lakes that hide the terrain that is submerged. However, the splays do tail off and their slopes can be very perceptible as compared with bodies of water which conform precisely to the surface of the planet (with dynamic perturbations of course). It seems that the creation of these erotional features could be done fairly automatically where material is removed from high structures and deposited into nearby low valleys. If Terragen does not have the built-in features to erode an automatically generated terrain into one that shows weathering through time, it would seem that a sedimentary lens could be created in an area. You could take a height maximum of the two (general terrain vs sedimentary lens) to create a convincing splay deposit. The lens deposit would take on the colors of the parent material while the emerging resistent rock would retain its own visual characteristics. The two might contrast if of different composition. Of course, a top layer of dust from the particulate material from the deposit would tend have a blending effect on the emergent rocks (in addition to lighting interplay). How can Terragen 2 address the issue of erosion and deposit splays?
I use the slope constraints of a surface layer or the distribution shader. Stretching a power fractal or three in the y direction works for erosion runnels, when negative displacement is used.
Very interesting - I shall be trying those ones.
You would need to use a program that models erosion like that, like Geocontrol or Worldmachine 2 (although I've not used the latter), then bring the .ter back into TG.
What TG does do well above anything else, is allow you to throw as much distortion you like onto those .ter's. Which is where I think a lot of people miss understand what the strength of this app is. This is one of the primary reasons why you can't export, to the detail TG renders at, a mesh to put back into a 3d app. They just can't handle the billions of polygons as real x,y,z data.
Hetzen makes some good points. TG2 does have a built-in erosion shader that operates on Heightfield terrains only. This is because it's a pixel-level raster operation. Procedural erosion has only so-far been demonstrated by one person, and there is no open understanding of how his techniques work, nor any application available that realizes it. So practically speaking procedural erosion doesn't exist. TG2's heightfield erosion works fairly well. World Machine and Geocontrol 2, among others, do offer more control and feedback. A good approach is to build a base terrain in a 3rd party dedicated heightfield modeler then bring that into TG2 and add procedurals for ultra detail.
- Oshyan