hello…

first, if I haven't said this before…I love L-systems…good job SESI , although it seems like I'm the only person using them ..lol..

anyway…in an effort to refresh my memory about using metaballs as meta-test boundry objects (RFE - it would be nice to use any geometry for the test) I did a quick hip to test leaf creation using A: ! in(x,y,z) = J instead of the tutorial's ‘A: ! in(x,y,z) = A%’, J being just a little sphere

what should happen is that the l-system itself should only grow inside the merged metaballs > once it is ‘outside’ it should pop a leaf(sphere) on it's end…but there are a few little strays in this file :shock:

boundry_leaf_test.zip [arctor.com]

so I guess I'm just wondering if this is a bug or user error or just more L-system fun ?
thanks

Hi!


With the L-System-SOP is everything all right. It's your rules, which make it branch outside of the control-volume. In your rule1 simlpy erase the first ‘F’ and double your step-size. The reason for branching outside, is, that the point, which is tested to lie inside the volume, really lies inside it, but with your rule1, you step outside and then you branch. As noted above, if you delete the first ‘F’, the test is made at the branching point and all will be ok.

Frank

P.S.: There exists at least a second person, who likes and uses L-Systems (me!)

do you mean change:
rule 1 : A: in(x,y,z) = F -FA : 80

to
rule 1 : A: in(x,y,z) = -FA : 80
?

I did this and then set step size from 0.1 to 0.2
but I get the same kind of result….

I just changed it to:
rule 1 : A: in(x,y,z) = F -A : 80
and it seems to give the correct result, until about frame 260

I guess the question is: where is the test made?, I'm working under the impression that if A - meaning the element created at the end of the current generation - is outside of the test object then a leaf should be placed at the end of the line…
if this is right there really shouldn't be any way of having a leaf inside the test object…

here are some screen shots:
img 01 [arctor.com]
img 02 [arctor.com]
img 03 [arctor.com]
img 04 [arctor.com]
img 05 [arctor.com]

it not really a big deal…I'm just working on something and I don't want leaves poping up where I don't want them

Your L-system has another problem:
Houdini allows only 30 nested branches. Your rules create a much more nested string in relation to the square brackets .
Here is a scene, which demonstrates this:
http://wwwcip.informatik.uni-erlangen.de/~sifrfirs/PruneGrowingTotallyOut.hip [wwwcip.informatik.uni-erlangen.de]

huh…


the many branched system prunes incorrectly after only 5 generations….!!
who knew?

this means I'll have to start thinking a little more…damnit! lol
I'm planning on trying to fill a volume with a very dense lsystem with leaves outside the test boundry…think ‘intestines’ …but if I can so easily go beyond 30 nested branches, I'll have to do something differently.

how do I know if I have more than 30 nested branches?….
when I middle click on LSystem_with_much_branching I can see that the Lsystem String is huge and is probably deeper than 30…but if I set the generations to 5 and increase the step size to 0.2 and middle click again the Lsystem String is much smaller… >30 for sure…..?? but it still prunes incorrectly…there is something I'm not getting here…

arctor
… but if I set the generations to 5 and increase the step size to 0.2 and middle click again the Lsystem String is much smaller… >30 for sure…..?? but it still prunes incorrectly…there is something I'm not getting here…

Yes you're right. These settings definively don't exceed the condition of the 30 nested branches. So theoretically it should prune the correct way. Now I don't know any further, why this happens. Perhaps there's really a bug in the L-System-SOP?

ah good….
I was worried that I might have mental problems on top of everything else :shock:

sorry…just bumping it up top again….
anyone from SESI know what's up with this?
thanks

sorry…just bumping again…
tested the scene with 6.1.101 and I'm getting the same results.