How to match these rocks?

[sboerner]

I'm really terrible at rocks and find the process of making them time-consuming, frustrating and difficult, especially when you're trying to match real-world formations.

Having said that, does anyone think it's possible to replicate these shelved riverbed rock structures in Terragen? I can think of no way to replicate the sharp edges and blocky shapes. Tried using cubes as a base but the edges explode when I apply displacements. At the moment my (untested) solution is to rough in the shapes in Blender and Mudbox, then create a vector displacement map that can be positioned and detailed in Terragen. Curious to know if anyone has any other ideas.

[Dune]

You would need at least an angled strata shader with a bit of a mask to vary its stratification, and I'd say warping by a smooth voronoi or voronoi vector (blue nodes), that sort of setup. And displace up by these blue nodes in the first place, or use a very hard PF with some very hard fractal warping.
But I'm sure some others will chime in. Kadri made interesting rock shapes.

[sboerner]

Thanks, Ulco. I'll give that a try. The Blender > Mudbox > Terragen workflow has stalled because Mudbox insists on throwing a fatal error when I try to import a mesh with hard creases. (Have to say I'm not surprised. Mudbox is buggy buggy buggy. Seriously thinking of cancelling my subscription early and moving to ZBrush.)

Another option would be to rough in displacement maps in Photoshop and fine-tune in TG. But your suggestions sound better.

[WAS]

This is the type of inspiration that lead me to trying to do mars shake like rock structures. Its actually tricky with stuff like this getting masks to work well with rest of the terrain. 

Ill experiment with this again cause curious myself.

[Kadri]

If you want to have close looking rocks maybe modelling is still the best way.

But you could try of course what Ulco said and make kinda similar or better ones like here below.

This is a scene from 1 year or so ago i am still working now and then. Still not finished.
It is mostly strata, fractal warp, vortex warp...No blue nodes.


The first 3 images are from last year. The others from today.

[sboerner]

Kadri, thanks for all those examples and the screenshot. I really appreciate you chiming in. Struggling here. I've managed to get a rough shelving effect but it's really not usable. There are some pretty extreme numbers in the strata shader to try to mimic the rock faces, which are perpendicular to one another in real life. The renderer does not like extreme displacements so it results in a lot of artifacts.

I may end up modeling these but there are also issues with that and I'd prefer an all-Terragen answer to this. I'm going to take a break and study your network and give it another go later this evening.

[WAS]

Shearing more straight angled shapes may be a better approach.

[Kadri]

By the way when i say "no blue nodes" it is not something i brag... I am just not good with them
So if you can use them you might get out much better things most probably.

[Kadri]

When you begin to use higher numbers in the nodes try using higher numbers with the compute terrain-normal too.
There is sometimes a sweet spot where you can get more interesting results and less bad displacement.

The compute normal there is "2000" for example. Depends on the scene of course.

[Kadri]

You could use the fakestone approach too. Might even be easier.
I was going to use this for another thing but when you use a flatter stone it could work for you too.

Not all stones are good for this (the simple shape shader is just for excluding the other stones) as you know.
But you could mask them etc. or just export them as obj edit them to your liking and import again.

[WAS]

I'm working on something. The Y from a Voronoi 3D A vector (or convert to greyscale) makes for a good breakup of voronoi to "chisel" it along with some adjustments and such. Then some strata and shear.

[Kadri]

Looks promising.

[WAS]

Got a bunch of stuff I gotta take care of, and gotta head out in the morning so I may as well upload what I have.

Maybe it can be simplified or elaborated on.

[sboerner]

Thanks Was, Kadri. Both of those approaches are worth a look. I did try fake stones earlier, but tried to do it in one go so to speak. I like your idea of exporting then importing . . . maybe they could be translated and stacked.

Here is where I am at the moment. Looks much better. If a few populations of fake stones are stacked around and on top, something like this should work.

I've found though that the strata shader is not a true displacement. At least it doesn't behave like one. I'm not able to warp it or use the fractal warp shader on it. So the layers of strata end up being super regular. Might try using a displacement map instead, it would be simple enough to make a linear gradient and tile it.

Done for tonight. Tomorrow is another day.

[Dune]

I'll have a go at it too, today. You're awakening my experimentation drive