> * this line needs to be 1/3 the length of that line > * these set of lines should start 50mm left of this line Remember that you're working with points. So,

> * this line needs to be 1/3 the length of that line > * these set of lines should start 50mm left of this line Remember that you're working with points. So, to express the length of a line, you need something like (x1-x2)^2 + (y1-y2)^2 . If you just wanted to do things like "this point is +(0,10) of this other one", you're doing a really simple constructive system, which is easy to evaluate, but not anywhere near as flexible or powerful. ImplicitCAD/OpenSCAD trivially do that, just without a nice interface.