Scattering over surfaces

mr-miley · February 13, 2007, 11:19:56 AM

Hi there all

OK, I am going to ask a really stupid question now..... In old Terragen, if you wanted to scatter a different colour over a surface layer (eg. darker patches of rock over lighter etc.) you would use the Fractal Noise slider in conjunction with the Coverage slider to break up the colour you wanted to overlay (ignoring altitude and slope constraints) After mucking around in TGTP with a surface layer over the base colour layer, I am intrigued as to how you are meant to do this. In my ignorance, I presumed that the Fractal Breakup in the bottom part of the surface layer window would take care of breaking up the colour (increasing/decreasing the scales etc in the power fractal settings letting more or less of the base colour show through) However this is not the case. The only thing that seems to break up the layer coverage is the coverage slider, whatever you put in the power fractal settings doesn't seem to make a damn bit of difference (and I have been playing round with this for a good few hours, trying settings from 1 to 100000 etc)
I found it far easier to add a power fractal as a surface shader to get distributed "patches of colour" which is fine by me, I am just intrigued as to why the power fractal breakup in a surface layer doesn't seem to do anything.
Anyone got any Ideas?

(And yes, I did have the tick box for Fractal Breakup ticked)

old_blaggard · February 13, 2007, 11:54:32 AM

I personally haven't experimented much with surface layers. I find that Power Fractals with a color range is the best way to apply color (in my opinion), and that if I need to constrain the color I use a distribution shader.

mr-miley · February 13, 2007, 11:56:32 AM

Thats what I am begining to think too. Ta for the reply

bigben · February 13, 2007, 06:10:53 PM

To get the fractal breakup to have some effect you should have the coverage set below 1 (which is effectively cover everything)

Will · February 13, 2007, 06:25:28 PM

All that I have done with them so far is using them to make oceans for my orbital renders (instead of using a planetary shader).

But if I figure anything out I'll make sure to post it here for you.

Regards,

Will

Oshyan · February 13, 2007, 10:54:23 PM

The current Surface Layer breakup settings aren't necessarily intuitive. As Ben said you need to have coverage below 1 for Fractal Breakup to have any effect. If you put it to 0.5 you should have a surface controlled by Fractal Breakup as you'd expect. Then adjust Breakup strength in the Surface Layer and possibly scale in the Breakup Shader itself (similar to the Depth/Scale setting in TG 0.9). Do post again if this doesn't give you the intended effects. Power fractals can be used instead of course, but they simply can't stand in for Surface Layers in many respects (although they're obviously more powerful in other ways).

- Oshyan

mr-miley · February 14, 2007, 03:16:09 PM

Ta very much all for the replies

. Bigben and Oshyan, Ta for the advice. I had tried with the coverage set to less than 1 and it did break up, but it looks pretty much the same no matter what I set the fractal breakup to. Never mind. I'll just have to keep potching (Welsh word) till I get it right. Thanks again for the advice.

Miles

Rob Allen · February 16, 2007, 01:27:33 PM

Try modifying the fractal breakup itself, it works just like any other shader. You can set feature scales, or change the noise characterstics to achieve a wide variety of breakup effects, including fades, scattering, and clumping, just to name a few. Many of these effects work quite well when used with the altitude and slope constraints of the surface layer itself.