topic Re: Split face into rectangular pieces in ArcGIS CityEngine Questions

Split face into rectangular pieces

MagnusLundevall — Fri, 10 Feb 2023 14:34:42 GMT

I have a planar face that I want to split along x into rectangular pieces, see enclosed figure. I have tried to examine the pivot pos of the edges with comp(fe) to find the x-positions for the split but without full success.

Any suggestions for solution in CGA code? Is the question clear enough?

Re: Split face into rectangular pieces

ThomasFuchs — Mon, 13 Feb 2023 16:23:41 GMT

Hello @MagnusLundevall

Thanks for this interesting question. Please try this approach using comp(v) and sorting the vertices by their pivot.px

version "2022.1" XPos = comp(v) { all : pivot.px } SortedXPos = XPos[sortIndices(XPos)] const EPS = 0.01 calcNextVertexLoc(positions, i) = case i < geometry.nVertices: case abs(positions[i] - positions[0]) < EPS: calcNextVertexLoc(positions, i+1) // check next vertex position else: positions[i] - positions[0] else: scope.sx getSplitPos = calcNextVertexLoc(SortedXPos, 2) @StartRule SplitRecursive --> split(x) { getSplitPos : Rectangle | ~1 : SplitRecursive } Rectangle --> color(rand, rand, rand)

Re: Split face into rectangular pieces

MagnusLundevall — Thu, 16 Feb 2023 06:36:57 GMT

Thanks for quick response. This is along the lines I have tried but much more elegant. It works in general but not for faces in certain orientations. I suspect I need to align the scope in some way. Any advice here?

To isolate the orientation problem I have made a simple shape where I try to apply SplitRecursive for each side face. Seems not possible to attach a scene here so I give the shape vertices instead. I have tried various kind of alignScope but without success.

@StartRule Init --> comp(f) {side: SplitRecursive | all: NIL}

Here is the current result. In this simple example I expect one Rectangle for each face.

Re: Split face into rectangular pieces

ThomasFuchs — Thu, 16 Feb 2023 14:12:24 GMT

The approach only works for horizontal and planar Shapes like building footprints. The axis of pivot and scope must be aligned.

Generally, rectangles can be created with the innerRectangle operation.

Re: Split face into rectangular pieces

MagnusLundevall — Mon, 20 Feb 2023 11:19:45 GMT

Oh, what a pitty. And there is no way to align the scope such that it can work?

I read about innerRectangle but don't see how it can be used to solve the example in the first post. Can you?