Colour distribution on surfaces

[kevnar]

I've been trying to figure out a way to get colours to show up stringy and veiny looking on surfaces. I've tried a few different methods but all I ever get is the speckled look.

I'm looking for something like this:http://www.healingcrystals.com/images/striped_brown_jasper_2.jpg

But instead all I get is this: http://z.about.com/d/geology/1/0/4/K/1/loboscobbles.jpg

The best I've come up with is getting the speckles to sort of follow a pattern by increasing the fractal break up to 1, and cranking the colour offset of the power fractal down to about -0.5. It's still not perfect though.

I know it can be done. I've seen people do it. It probably has something to do with functions which I know nothing about. Please talk me through it in baby steps, if you can. Thanks in advance.

[j meyer]

Hi,
one thing you could try is stretching the noise and/or warping it.

[kevnar]

Yeah, I tried that but all the rocks looked the same, with tiger stripes of colour. I was hoping for more solid, swirly stripes, as in the picture.

[Henry Blewer]

When I create high stratus clouds, I use this method. First I give the cloud layer a HIGH altitude. Now comes the part which pertains to your question.

In the density shader, I change the lead in scale to 80,000, and the feature scale to 2450. The smallest scale to 0.1. Now this scale is huge, but you can scale it down. If your rocks are say 10 meters/units, then the feature scale would be 0.005. These numbers need to be tweaked so they fit your idea of what you are trying to do.  Now go to the tweak noise tab. Change the top button from Perlin to Ridged. Change the noise variation so it is larger, try 2. The buoyancy and clumping control how the noise behaves. The reason you need to use ridged, is it is kind of like a marble texture. This should give you what you're looking for.

[Cyber-Angel]

Hi Kevnar,

Could you tell me what settings your using to get the speckled effect your not looking for, but I am?



Regards to you.

Cyber-Angel 

[Oshyan]

Be careful with extremely small scale settings. It can cause rather extreme errors in scene rendering. If your scene goes black when you use values below 0.01, that's probably the cause.

- Oshyan

[Henry Blewer]

I did not know about the small scale issue. I have not run across it. It's easy enough to scale things up. The default planet/landscape is large enough to look right with things adjusted to a ten meter scale. Could that be why when I render sometimes the creases have black 'shadow' things?

Thanks!

[kevnar]

Hi Kevnar,

Could you tell me what settings your using to get the speckled effect your not looking for, but I am?



Regards to you.

Cyber-Angel 

The speckles are just a surface layer added as a child of the fakestones with a coverage of about 10-20%. Change the colour to something other than the fakestones colour. Voila! Speckles.

[kevnar]

Can someone explain what Leadin scale does? I'm finding I get better results with the leadin scale set to zero. The fractals are crisper, more sharp and vivid at finer details. As far as I can tell, it's a sort of blurring/blending function for the fractal noise. Can someone explain it to me better than that? Thanks.

[Kevin F]

Can someone explain what Leadin scale does? I'm finding I get better results with the leadin scale set to zero. The fractals are crisper, more sharp and vivid at finer details. As far as I can tell, it's a sort of blurring/blending function for the fractal noise. Can someone explain it to me better than that? Thanks.

just read the docs!

i.e.http://forums.planetside.co.uk/index.php?topic=9

[kevnar]

Actually, the one sentence they give you isn't much help. That's why I asked. 

[Henry Blewer]

Based on my experience, the lead-in scale is the largest scale(size) that the power fractal/density shader can cover. For instance, when I do the highest wispy cloud layer (cirrus) I like to set the lead-in scale to 80,000. The scale size varies by the altitude.  So, if the altitude is 11,500, I tend to use 1250 - 1800. The numbers in the three boxes at the bottom of the teak noise tab stretch the pattern of the fractal. They are X, Y, and Z axis manipulations.
If you leave the lead-in value at 1000, the scale setting needs to be about ten percent of the lead-in. To get the ribbon effect, I would use the axis stretch inputs.
Do some clouds with the different teak noise selections; perlin, billowy, etc. Clouds at the default quality values render quickly. It's a good way to find out about the power fractals power.

[tempaccount]

Yes, lead-in scale is the largest element present in your fractal, while smallest scale is the smallest. Feature scale depicts the size of the most common element in the fractal. The units are in meters.

As an example, lets say you have a fractal with a lead-in scale of 10000, smallest scale of 1 and feature scale of 10. This would make most of the elements in the fractal 10 meters, and a few, big elements with largest of them being 10km. Most likely your fractal would look pretty empty, with small streaks of blotches spread over here and there. If you drop the lead-in scale to 100, your fractal would be a lot more even.

I hope that cleared up something. NWDA has an article about the power fractal, I think it covered it up pretty well: http://nwda.webnode.com/news/understanding-the-power-fractal/

[kevnar]

I'm thinking I can play with the clumping feature in the "Tweak Noise" tab to get the effect I want in the colours. I'll try a few things and post the results I come up with. I came across a description of it in the tutorials on terrain generation. It turns out that's the feature I'm looking for with colour distribution as well. I also made a much more realistic prairie scene with the clumping set a lot higher on the fractal terrain. 

Thanks for the description of Lead-in scale. That makes much more sense. Not sure why it's called "Lead-in scale" and not "Largest scale". That would have been more intuitive.