I've discovered a programme which seems to be the LS equivalent of Apophysis in 2d or XenoDream in 3d: Context Free Art http://www.contextfreeart.org/ I describe it thus because it allows LS programming plus a lot more non-LS work, and because its language is at least related to LS. Are you aware of it?

As far as IFS goes... one difference between Apohysis IFS and that of Fractint is a great feature of the latter about which I have not found any literature, so I might as well claim credit for discovering it unless someone else can correct me. This is that if you start off with a shape like a square filled *solid* with holons, and then simply alter the numbers in the 7th column - those which deal with probability - you end up with fantastic fractal textures instead of the solid fill. (These probability numbers should still sum to 1.) I have done a huge number of explorations of squares in this manner, some with triangles, and also discovered new textures for the Dragon Curve and TwinDragon. I was waiting for the new Fractint version to reveal this, but now seems a better time to point it out, in the context of a plea not to do away with such a possibility. (It doesn't seem to work in Apophysis, or at least works differently; I haven't tried it in XenoDream yet.)

I don't understand all of the details of your letter below about IFS, but am eagerly awaiting a demonstration of what it all means.

Tony Hanmer

On 8/1/07, Richard <legalize@xmission.com> wrote:

I'd appreciate input on you regarding the L-systems stuff I posted to
the list recently.  For L-systems I want the code to ultimately
approach the realistic plant rendering capability of Prusinkiewicz's
code.  We're a long way off from that, but that's the target.

For IFS, right now the code only supports probabilistic 2D/3D IFS.  I
want to add more IFS types like language restricted IFS.  For
rendering, I want to use OpenGL to give interactive manipulation of
the IFS rendering as well as a design interface that's better than
editing transformations coefficients in a text file.  I also want to
use "point sprite" rendering for IFS which will give them more "body"
with fewer iterations and still be interactive.  I've also thought
about doing a potential rendering technique where rendered iterations
define a charge in space and the rendering draws the potential
resulting from such a charge.  Finally, I want to extend the text file
specifications so that you can specify the transformations in a
transform language rather than as just raw coefficients.  That way you
could naturally right s(sqrt(2)/2)*r(180)*t(0.5,0.5) to mean "scale
uniformly by sqrt(2)/2, then rotate by 180 degrees about the Z axis,
then translate by (0.5,0.5)".  I've come across a very nice recursive
descent parser framework for C++ -- the spirit module in the boost
library -- that will let me make a number of improvements across the
board in fractint, both for formula types and for IFS and L-system
types.
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