Thomas de Groot <tho### [at] degrootorg> wrote:

Thanks for making the render.  Looks better than my sphere - which looks like a
cheap hard-rubber bowling ball, or the foam they use in sofa cushions.  :D

Needs 0.2-0.3 more turbulence. ;)

> The granite pattern is (almost) correct (without the turbulence).

I don't know what you mean.

> It also explains more comprehensively the original name: Mahogany. The
> colour is similar to mahogany wood. Afaiac, I believe I should follow
> that path in the first place and maybe disregard my own lighter version
> (or not). Not sure yet. What do you think?

Well, there are myriad samples available at stonecontact-dot-com, all of which
fall under the blanket/umbrella trade name of Dakota Mahogany and which have
widely differing "color maps".

I think we need to alternate in our approach to this, and on the one hand try to
formulaicly mimic the underlying patterns and sub-patterns, but on the other
hand not forget that we can do some good ole' raytracing sleight-of-hand and do
everything we can to fool the eye and mind into believing that they see
something that is not there.

One thing I thought of was to take a/some granite photos and run some
edge-finding filters on them to see what pops out.

I'm curious about the rgb color mapping - the individual values - but also,
given an individual grain region, what is the rgb variation across it?  How much
secondary or tertiary pigment is patterned into the grain?

Is there a way to estimate the grain sizes from the photos?  Or maybe there is
statistical data in the literature?

I ran across a neat conformal mapping image with circle packing that looked like
a good mathematical way to get discrete regions with good grain-size variation.

AFAIK, we're using straight Perlin noise right now for granite.   Doing floor()
on each of the axes produces the cells {} pattern.  I'm thinking if we could
split the difference.... maybe with the step trick and/or select ()

Also need to keep in mind that the base pattern might just be a guide, and the
final "look" is going to likely be a result of layering textures/materials.
Hard to visualize.

And lastly, there were the brick pattern and random hexagon color threads that
employed methods we might be able to use here.

http://news.povray.org/povray.general/thread/%3C5ae17c9c%40news.povray.org%3E/?mtop=422221&moff=10

http://news.povray.org/povray.binaries.images/thread/%3Cweb.5ad633941828641ca47873e10%40news.povray.org%3E/?mtop=422589

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