I'm trying to write an expression(involving chops) in an l-system rule similar to say:

Achopf(“/ch/ch1/file1/chan0”, $F)>0.5)=F

This kind of expression isn't working for me. Does anyone know if chops are supported within l-system SOPS?

Cheers
Henster

someone correct me on this if im wrong, but i don't think you can do many expressions at all in your l-sys rules. not even $F.. which kinda sucks cause that would really really nice if you could..

from the manual:

71.12 EXPRESSIONS

In the earlier example, the expressions 0.5*i and 2*j are used. In fact, expressions can be used anywhere a numeric Þeld is expected. Currently the following symbols can be used within expressions:

( ) brackets for nesting priority
^ + - * / % arithmetic operators
min() max() sin() cos() asin() acos() pic() in() supported functions
== != = < <= > >= logical operators
& | ! logical operators: and, or, not
b c d OP b, c, d parameters after expansion
x y z current turtle position
g age of symbol
t time (generations) of L-system
a OP angle parameter
T OP tropism (gravity) parameter

The pre-deÞned variables above should not be used in the arguments of the prede-cessor. For example:
A(a,b) = B(a*2,b*2)WRONG (a is the OP Angle parameter) a<b (A,B) = b(A+1,B)RIGHT
The last statement is correct because a and b are used as symbols and not variable names. A and B are correct because variable names are case sensitive.

L-SYSTEM SPECIFIC EXPRESSION FUNCTIONS

pic(u, v, c)Using the image speciÞed with Pic Image File, thisfunction returns a normalized value (between 0 and 1) of the pixel at the normalized coordinates (u,v); c selects one of four channels to examine: 0 - grey 1 - red 2 - green 3 - blue

in(q, r, s)Given a MetaTest input source containing a metaball geometry, this function returns a 1 if the point (q, r, s)is contained within the metaball, and 0 if not.Use in(x, y, z) (the letters x, y, and z are special andcontain the X, Y, and Z location of the turtle) to testwhether or not the turtle is currently inside the metaball to create pruned outputs.


hth,

dave

If you look at the help in 6.1 within the Lsystem SOP, I believe there's an example on how to do expressions.

you could also use the custon variables (a, b, c etc) for your expressions, then use those values in your rules