How do I make river gravel?

Started by Cyber-Angel, May 25, 2009, 10:43:14 am

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Cyber-Angel

May 25, 2009, 10:43:14 am Last Edit: May 25, 2009, 10:45:09 am by Cyber-Angel
Hi,

I wonder if some one can help me, I am looking to make river gravel using fake stones shaders for an image that I hope to post a WIP of soon; however I cannot workout how to make the fake stones look realistic both in terms of shape (Rounded like water tumbled gravel would be) and the realistic sizes, distribution and coloration (I don't want to buy a tech pack, thank you).  ;D

Any help would be gratefully received. You can PM of you don't want your method/s of the forum.

Regards to you.

Cyber-Angel       

FrankB

Just give your fake stones a reduced tallness, and an increased pancake effect. If you now plug into the surface input a power fractal with the appropriate sizes for feature, lead and smallest scale, and appropriate amount of displacement, you will be getting there. You can also "pump up" the stones evenly by applying a little offset displacement.

Regards,
Frank

Cyber-Angel

Thanks Frank I'll give that ago.

Regards to you.

Cyber-Angel :)

kevnar

Check out chapter two here: http://nwda.webnode.com/news/making-of-wilderness/

It's got a pretty detailed description on using the fake stones.

Cyber-Angel

Quote from: kevnar on May 27, 2009, 10:49:26 am
Check out chapter two here: http://nwda.webnode.com/news/making-of-wilderness/

It's got a pretty detailed description on using the fake stones.


Thank you for that, but I know a few things about the fake stones shader already; I was asking about a specific use of the fake stones shader for an image I'm working on at the moment. Thank you for showing me this! ;D

Regrads to you.

Cyber-Angel 

Henry Blewer

I used to use just the power fractal for the fake stones surface shader. This often gave me 'exploding' rocks. Now I make a new surface layer. This seems to stop the 'explosions'. It also lets the fake stones scale to the sizing work.
Within the new surface layer, it's simple to add more colors and/or displacements. For the color, just add more child surface layers, and adjust the coverage with the slider. On the displacements, you can add a power fractal to the displacement tab input, and/or add power fractal child layers.
http://flickr.com/photos/njeneb/
Forget Tuesday; It's just Monday spelled with a T

domdib

Just to be clear njeneb, where are you plugging the surface layer into? Or does the Fake Stone shader plug in to it?

Henry Blewer

May 28, 2009, 02:53:24 pm #7 Last Edit: May 28, 2009, 02:58:31 pm by njeneb
I start with three main surface layers; hills, sands, and grasses. The hills layer normally would get fake stones shaders with lateral displacements, the largest scale set to 1/4 of the hills height. I use slope for control of 'where' the hills start.
Next, I move onto the sands shader. I use the shaders base color, something between the extreme dark color and the extreme light color. This also uses a slope control, which I adjust to whatever slope angle I think looks right. The extreme dark child surface layer gets about 0.7 coverage. Then I do the same with the light sand child surface layer. Both layers get very small displacements along the normal. These give nice color variation of the total surface. Since the Parent surface layer is farther down the hierarchy, some of the hill shader is covered as well.
Now select the main sand surface layer. Add the smallest and largest coverage fake stone shader from the child menu. Little rocks get covered by larger rocks. I use surface layers for the surface shader input. This seems to stop the exploding rock difficulty.
Set the scale to something you can just see on the preview. Coverage of 0.5 is a good starting point.
You can create new fake stone shaders the same way. You can assign the same surface layer from the first fake stone shader. Just incrementally increase the scales. The coverage should be reduced, maybe by 1/3 for each fake stone shader added.

I hope this clears up what I am trying to say. As an American, English is not my best language. It is the the one I speak (and write), but I am not very good with it. I suffer from the idea that everyone knows as much as I do, so I skip parts of explanations. If you have more questions, I'll be glad to give whatever help I can.

A note on power fractals. Don't use them for the color function or displacement noise of the fake stones shader. The power fractal displaces by a range. This is both positive and negative. It's what is used for terrain creation, so the pos/neg is necessary. They can later be used from the surface layer the fake stones shader points to from its input. I would only use them for coloring from within the surface layer. In the surface layer displacement used for the fake stones shader, I use the perlin noise function. The perlins noise scale I use is about 1/5 of the fake stones scale. Any number can be used for the seed.

http://flickr.com/photos/njeneb/
Forget Tuesday; It's just Monday spelled with a T

rcallicotte

I use power fractals for all kinds of stuff, including Fake Stones (see the File section for examples).  You just need to watch your values.  If anyone has ever gone through the Volker terrain tutorial, you'll know immediately the beauty of a tuned set of Power Fractals.  efflux was also very good at making these power fractals do amazing magic.   And, if I remember right, Seth used power fractals recently to create his interesting looking metal stones.
So this is Disney World.  Can we live here?

domdib

Thanks for such a comprehensive response, njeneb.  :)

Oshyan

The "exploding stones" issue is actually due to a setting in the Fake Stones shader. Turn off "Blend as Density" and it should fix the problem.

- Oshyan

Henry Blewer

Thanks Oshyan! It's a curious feature. I have been thinking of how to exploit it, but so far that has eluded me.
http://flickr.com/photos/njeneb/
Forget Tuesday; It's just Monday spelled with a T

Seth

Quote from: njeneb on May 28, 2009, 02:53:24 pm



A note on power fractals. Don't use them for the color function or displacement noise of the fake stones shader.



and I say : use powerfractal as colour function and displacement noise of the fake stones shader ;D
well, that's the way I do...