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Sand
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1998-02-13
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Date: Thu, 9 Oct 1997 12:35:21 -0700
From: "Hall, Michael R." <mikeh@RETAILPRO.COM>
Subject: [IML] Chat: Sand Texture
I've had an idea for the texture programmers out there:
How about something that can simulate a sandy surface?
I've been wondering how to go about creating this, and I know that I can't
use roughness (I have to render the same image three times and combine them
to get a final image, but roughness never renders the same way twice). I
suppose I can try rendering using FractBump.itx at a very high resolution
and then scaling the image down, but sand is composed of a silicate and
often there is a rainbow like pattern seen from the refraction of the
crystals, and I am not certain how to get this.
Anyone have any ideas? Even an image map of sand at this point would be
extremely helpful. I need it to finish the rush "diamond" project I
described last week.
Thanks a lot!
Micheal Hall
---------------------------------
From: Matt Kropp <cmkropp@HOME.NET>
How about using a layer or two of the colornoz texture. I don't know if
fractal bump would actually be necessary. I guess that would depend on how
coarse the sand is, and how close the camera is to the sand.
You shouldn't use roughness in animations. The documentation says it's
completely random in every rendering, so it will look like snow on TV when
animated.
One thing you might want to play with is Simon F.C. de Rivaz's diffuse
texture. It used to be on his web site, but I can't find it any more. Maybe
I could put my copy of it on my web site if it's okay with him. Anyway, the
diffuse texture keys off the roughness setting and converts it into a change
in luminance. It's useful for modeling very diffuse materials like sand, as
well as other things. Think about how the full moon looks. It looks more
like a disk than a sphere. This is because the dusty surface scatters
reflected light over such a broad angle (very diffuse) that even the sides of
the sphere appear to be just as brightly lit as the front of the sphere.
Now the diffuse texture wasn't exactly designed to simulate that, but it can
add a nice luminance to surfaces. The way you use it is first apply a
grayscale bitmap and have it affect the roughness of the object. Then load
the diffuse texture after the bitmap. That's it. For your application I
would suggest a random noise pattern for the bitmap.
Matt Kropp
http://members.home.net/cmkropp