Creating Arches in CE question

Anonymous User — Wed, 25 Aug 2021 12:43:19 GMT

I've been messing around with equations to create bridge arches but I cannot figure out why one equation will not work in CityEngine.

I've been using Desmos graphing to figure out my equations and you'll see here that I have 3 graphs which I have designed to be similar lengths and heights:

upward parabola
downward parabola
sine wave

I can successfully get the two parabolic functions to work under an extrude but I cannot get the sine wave to work under the extrude.

@Hidden attr segment = 1 @Hidden attr BridgeSpanL = geometry.du(0,unitSpace) const Pi = 3.14159 const Bx = Pi/BridgeSpanL @StartRule BridgeSpan--> set(BridgeSpanL, geometry.du(0,unitSpace)) split(u,unitSpace,0){~segment: BridgeArch(BridgeSpanL,split.index)}* BridgeArch(BridgeSpanL,n)--> extrude( //-(pow(split.index,2)/BridgeSpanL)+split.index //Parabolic Curve for typical Arch Bridge //pow((split.index-(BridgeSpanL/2)),2)/BridgeSpanL // Inverse Parabolic Curve //(BridgeSpanL/4)*(sin((Pi/BridgeSpanL)*split.index)) (BridgeSpanL/4)*sin(Bx*split.index) )

Although I can get a sine or cosine wave to work, I cannot get the period/frequency of the sine wave to behave as I expect under the function. If I could, I think I could create some more interesting arch patterns.

Is it my code, my math (probably), or is this a bug or a limitation of the extrude?

Parabolic Arch

Above: Parabolic equation working.

Flat Sine Wave

Above: Sine wave equation not working.

Above: Sine wave sort of working but without the a frequency parameter (Bπ or 1/Bπ)

Also, does Pi π have a built-in for CityEngine? I feel like it should.

Re: Creating Arches in CE question

Anonymous User — Thu, 26 Aug 2021 12:44:56 GMT

The ESRI Fence code gave me a few new ideas about how to create arches. For the picket fence they manipulate the scope.sy of the horizontal span with some parabolic equations to achieve some unique forms. None using wave functions though.

topic Re: Creating Arches in CE question in ArcGIS CityEngine Questions

Creating Arches in CE question

Re: Creating Arches in CE question