topic Shape perimeter in ArcGIS CityEngine Questions

Shape perimeter

AleksandarLalovic — Mon, 07 Oct 2013 12:36:40 GMT

Is there a way to calculate shepe/block perimeter?

Re: Shape perimeter

MatthiasBuehler1 — Mon, 07 Oct 2013 16:09:13 GMT

Hi,

In CGA, you can use geometry.area() to find a shape's area.

Check the docs on how to precisely use it.

If you report the area and select all shapes, the Reports tab in the Inspector will show the sum of all areas.

But since CGA operates only on single shapes, CGA has no way to 'collect' reported data of it's neighbor shapes in the same Block.

Python scripting may give you a few workflow options though.

Ok ?

matt

Re: Shape perimeter

AleksandarLalovic — Wed, 09 Oct 2013 14:04:04 GMT

Im not talking about area. Im trying to find shepe perimeter/circumference, sum of the length of all edges.

Re: Shape perimeter

MatthiasBuehler1 — Thu, 10 Oct 2013 13:24:04 GMT

Ah.

that's currently not directly queryable with a function.

I recommend :

comp(e) { all : report("edgeLength", scope.sx) NIL }

ok ?

m.

Re: Shape perimeter

AleksandarLalovic — Thu, 10 Oct 2013 13:59:11 GMT

For the reporting this works just fine but if i would like to use this value in a rule file i guess its not possible?

Re: Shape perimeter

MatthiasBuehler1 — Fri, 11 Oct 2013 16:52:17 GMT

Hi,

there's one more, much more complex way to obtain directly in CGA.

otherwise, I'd recommend to use Python to quickly take the reports and write them as an object attribute.

let me know if you're interested in the complex way. I'll need to adapt an other existing rule for this, will take a bit of time.

matt

Re: Shape perimeter

MatthiasBuehler1 — Fri, 11 Oct 2013 16:58:33 GMT

after thinking for a minute, you could do something like this :

@Hidden attr perimeter = 0  Lot -->     extrude(1)     set (perimeter, geometry.area() - 2 * (geometry.area(bottom))     comp(f) { bottom : reverseNormals Gotcha. }

the idea of course being that you take the full surface after the extrusion, subtracting the bottom and top area, then dividing again by the extrusion height.

cheers !

matt

Re: Shape perimeter

AleksandarLalovic — Tue, 15 Oct 2013 08:16:46 GMT

Wow, great. Didnt see that coming. Realy nice trick with the area. Thanks