what's the meaning of $ in Lsystem?I'm confused.
for example :
premise X
rule1 X=+$+

why is angle like that?

From the documentation: “Rotates the turtle so the up vector is (0,1,0). Points the turtle in the direction of the point (x,y,z). Default behavior is only to orient and not to change the direction.”

I've honestly never attempted to use it, so I'm not sure of it's effect based on that description. Not sure what orienting without changing the direction means.

It will literally do what it says on the box. It will point the turtle towards a fixed point in object space given by (x,y,z) this is not a vector for a direction but an actual point in space. It's a Look-At if you like.

Note that since this is in object space if you use it like i did here to point the lsys at a null it only works as long as you dont transform the lsys geo object.

If you only use $ without the (x,y,z) it will simply orient the turtle to the up vector of (0,1,0) without pointing it to a new direction. However the change in orientation will of course affect subsequent angle changes with for example + and -

Fabian

thanks,now I maybe understand $(x,y,z).
houdini is so difficult to learn :cry: