Author Topic: How do I make river gravel?  (Read 5319 times)

Offline Cyber-Angel

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How do I make river gravel?
« on: May 25, 2009, 02:43:14 PM »
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       
« Last Edit: May 25, 2009, 02:45:09 PM by Cyber-Angel »

Offline FrankB

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Re: How do I make river gravel?
« Reply #1 on: May 25, 2009, 02:54:20 PM »
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

Offline Cyber-Angel

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Re: How do I make river gravel?
« Reply #2 on: May 25, 2009, 03:07:26 PM »
Thanks Frank I'll give that ago.

Regards to you.

Cyber-Angel :)

Offline kevnar

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Re: How do I make river gravel?
« Reply #3 on: May 27, 2009, 02:49:26 PM »
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.

Offline Cyber-Angel

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Re: How do I make river gravel?
« Reply #4 on: May 27, 2009, 04:08:05 PM »
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 

Offline Henry Blewer

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Re: How do I make river gravel?
« Reply #5 on: May 27, 2009, 08:37:18 PM »
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.
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Offline domdib

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Re: How do I make river gravel?
« Reply #6 on: May 28, 2009, 02:22:37 PM »
Just to be clear njeneb, where are you plugging the surface layer into? Or does the Fake Stone shader plug in to it?

Offline Henry Blewer

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Re: How do I make river gravel?
« Reply #7 on: May 28, 2009, 06:53:24 PM »
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.

« Last Edit: May 28, 2009, 06:58:31 PM by njeneb »
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Offline rcallicotte

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Re: How do I make river gravel?
« Reply #8 on: May 28, 2009, 08:31:43 PM »
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.
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Offline domdib

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Re: How do I make river gravel?
« Reply #9 on: May 28, 2009, 08:59:21 PM »
Thanks for such a comprehensive response, njeneb.  :)

Offline Oshyan

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Re: How do I make river gravel?
« Reply #10 on: May 29, 2009, 02:54:34 AM »
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

Offline Henry Blewer

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Re: How do I make river gravel?
« Reply #11 on: May 29, 2009, 05:15:49 AM »
Thanks Oshyan! It's a curious feature. I have been thinking of how to exploit it, but so far that has eluded me.
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Offline Seth

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Re: How do I make river gravel?
« Reply #12 on: May 29, 2009, 06:16:00 AM »



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...

 

anything