rock formations anyone?

[peejay]

create a terrain from a power fractal, plug a compute normal shader into it and then set the displacement to lateral only. This is your hidden terrain.
Now create a second terrain, any style you please - in the attached shot it's a basic perlin billows based rolling hills landscape. This is your visible landscape.
Now plug  a crater shader into your hidden landscape with a large negative depth value, and the crater shader will 'push' the hidden landscape through the surface of the
visible landscape to create something like these.

Anyone who's good at maths and node manipulation care to take this further to see if it's possible to get decent rock stacks and towers out of this?

[rcallicotte]

Cool.  Thanks for explaining.

[peejay]

this is what happens if you change the node order.
 
(edit)

or more precisely, using the same file this:

the towers are looking much better but the visible terrain is cracking up

[rcallicotte]

After I get through some stuff today, I'm going to play with this. 

[jaf]

Looks like the start of some hodo's?

[peejay]

OK, here's how the white tower rendered. Bits of it look promising - could make a cool sci-fi planet maybe, but the base is just wild. Plus, I have a sneaking feeling this is actually rendering inside out somehow, in which case once back face culling comes along, it might not work at all. Anyway, here's the tgd for those who like to play (and hopefully have better brains than mine)

good luck one and all....

[jaf]

Wouldn't have to be SciFi.  Check the image here:  http://tinyurl.com/yr3n3e

[peejay]

nice pic jaf.
Yes, hoodoo's is what I'm after, in fact the inspiration for this line of enquiry was a desire to replicate a pic I saw of Bryce canyon, but the whole thing needs to be 'calmed down' a bit in order to be believable. I can't do it because I don't understand what TG2 is doing, therefore it's trial and error which settings will affect the terrain in the way I wish. I'm hoping someone who actually 'gets' this program can pick up the experiment and knock it into shape   

[jaf]

Yes, I've tried making some 3D models in Lightwave and finishing them in 3D-Brush.  But your method may be better and faster.

Funny, I first saw the name "Hodo" several years ago but then when I did a search I couldn't come up with that many images.  But "Hoodoo" definitely solved that.

[peejay]

all adjustments on the crater shader:
basically decreased (or should that be increased) the negative depth value, increased the rim height, and set the rim softness to 0. That seems to have stopped the base rocks poking through each other.

The lateral displacement is still far too extreme in the base of the tower. (must go and explore the weird domed hills on the left )

EDIT:

well they're even weirder than I thought; check this out..

[Virex]

Something i just found out while playing with this: Increasing the patch size of the compute normal node will decrease the ugly crack effects.

I'm doing a lagre-scale render now to see if this technique can be used to create interesting shapes on normal terain. Havn't tried using it with an inverted crater yet.

[rcallicotte]

Also, the smooth terrain checkbox can be a friend...

[peejay]

"I'm doing a lagre-scale render now to see if this technique can be used to create interesting shapes on normal terain."

well spotted virex; something like this 'cliff house' for example?

This was produced with a perlin billows fractal in the hidden terrain,
feature scale: 427
lead in scale: 25000
smallest scale: 2
Displacement: lateral only
Displacement amplitude: 10.0113
Displacement offset: 198.854
Displacement roughness: 0.86785
Noise variation: 10
Multi Scale modulator
Buoyancy from variation: 3
Clumping of variation: 3

visible terrain:
perlin billows
Feature scale: 5000
Lead in Scale: 25000
smallest scale: 0.1
Displacement: Along vertical
Displacement Amplitude: 15.2588
Dispacement offset: 0
Displacement roughness: 0.45625
Displacement spike limit: 0.19375 (Continue spike limit checked)
Noise variation: 30
Multiscale modulator
BUoyancy from variation: 2
Clumping of variation: 5
Distort by normal: 5
1 Ocatve Perlin warp
Lead in warp amount: 0.75
less warp at feature scale

[peejay]

to show the variety of forms that can be achieved, all be it in a very haphazard way.

Again this is two terrains, one with displacement set laterally, the other vertically. This time the hidden terrain is modified with a power fractal on x & y axis via a redirect shader.

Does anyone understand what is happening here? More to the point - how to control it?

anybody? anyone at all....

[Virex]

Here's another example. I'm rendering it with an even higher patch size and some other tweaks now.