"Bald Eagle" <cre### [at] netscapenet> wrote:
> "And" <49341109@ntnu.edu.tw> wrote:
> >
> > Oh, ... I wouldn't like to make any detailed tree trunk "3D Model"(that is
> > another
> > challenge), I just generate a (3D)texture. I implement my texture in POV-Ray,
> > outputting "pigment {...}" as its final form.
>
> Naturally.  The wood pigment patterns we've almost all been using for the past
> 30 years are just a bunch of concentric cylindrical rings.   Seems to work well
> enough for most purposes.
> To add a bit of realism by simulating the cross-section of those 3D branches,
> the black hole warp can be used, and that's what I was thinking when I suggested
> looking this over - not copying the paper's method verbatim.
>
> So rather than create a whole 3D tree and then slice it (which would necessarily
> limit the pattern to the locus of the individually modeled tree), I was thinking
> that you could assemble a pattern of black hole warps using an L-system in code,
> which would then be used to define the pigment {}.

I just notice "black hole warps" this time. It seems it is a 'spherical'
distortion around a sphere-center?

However, I can make more natural knot shape by myself. I use function as pigment
input, it is more flexible than the built-in pigment-warp of POV-Ray. I still
need several months to integrate it with my GUI java program. But I will
investigate this feature(black_hole warp) for it being a convenient effect.


>
> I my mind, this would be very much like the way Tor Olav Kristensen uses a macro
> to assemble the terms of a long Bernstein polynomial function.
>

'Bernstein polynomial function' looks like some special function I know, but I
don't know this one.


> jr has also done a lot of development using the method of including the parsed
> text of temporary files to assemble complex data/code structures, as well as
> some pretty complex data "trees" - which might serve as inspiration to you or
> others for generating complex pigment pattern definitions.

Oh, jr had e-mail me and told me something, thereby I fix the 'locale' problem
of number quickly last time.


>
> TdG may have code of a similar nature in his vast archive, or have other ideas
> of his own about how to approach the branch/knot aspect of the wood pattern.

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