topic Re: Store a Shape in CGA in ArcGIS CityEngine Questions

Store a Shape in CGA

LesiMai1 — Sat, 11 Dec 2021 06:50:53 GMT

Hi,

I'm wondering if there is a way to store a parent shape to refer back to in CGA. I used the shapeO operation to randomly generate O-shaped area. And then I ran a comparison to see if the area is greater than a certain threshold. If not, I want to regenerate the O-shaped area again until it meets the criteria. My current cga creates a recursion. But I was wondering if I can get a hold of the parent shape the OShape was generated from.

OShape -->
   shapeO(rand(0, 5), rand(0,50), rand(0, 20), rand(0,20)){shape:X|remainder: Calc}
Calc -->
   case geometry.area > 60:
      extrude(10)
   else:
      OShape‍‍‍‍‍‍‍

Any pointers are appreciated!

Lesi

Re: Store a Shape in CGA

LR — Tue, 08 Aug 2017 11:10:12 GMT

You could store attributes in variables, like this: set(initialArea, geometry.area)

Re: Store a Shape in CGA

LesiMai1 — Wed, 09 Aug 2017 05:20:15 GMT

Thank you for the reply! I may not have been clear when I posted the question. But I'm wondering if there is a way to store the actual shape but not just the attributes.

Re: Store a Shape in CGA

LR — Wed, 09 Aug 2017 22:47:29 GMT

I don't think you can. What are you trying to do?

You can more or less store a shape with Python (getVertices and getAttribute), if that helps.

Re: Store a Shape in CGA

LesiMai1 — Thu, 10 Aug 2017 15:26:38 GMT

I was trying to generate a shape with random dimensions on a lot. But if the area of the new shape is under a certain threshold, I want to regenerate the shape until it meets the criteria.

Re: Store a Shape in CGA

LR — Fri, 11 Aug 2017 00:11:49 GMT

To my knowledge this won't be possible with CGA alone. CGA only goes in one direction, and you'd have to return to a previous state. You can call a previous rule, but it'll be applied to the current state.

You have to re-run the rule until the area condition is met. Remove the recursion and run the script until the object is generated. Don't forget to update the seed, or you'll always get the same "random" numbers.

You can either do it manually (ugh) or automatically with Python (using reporting to export a variable to check in a loop).