l-system question

[FrankFirsching]

You can use the same variables in different rules. Houdini will set the corresponding values based on the current token. This means, that the variables are local to the rules, not global to the whole l-system. In the premise you only define a starting-value for the variables needed by the token (if you omit them, Houdini sets the default-value, which is normally zero).

I changed your example to demonstrate this:

Premise: [A(1,1)]G(1)[A(2,2)]
Rule 1:    A(i,j)=^(90)B(i,j)
Rule 2:    B(i,j):j>0=F(i,j)B(i/2,j/2)

The "G", "^" and square brackets in the premise and rule 1 are only to separate the 2 objects. But you notice, that A is instantiated 2 times, each with different values. Houdini now sets the values of i and j to 1, when it derives the first occurance of A and the variables are set to 2, when replacing the second occurance of A.