topic Re: SplitArea Function in ArcGIS CityEngine Questions

SplitArea Function

AbhishekSobbana — Tue, 23 May 2017 02:11:32 GMT

Hi, I am trying to break down a parcel using splitArea(x/z) function some how it says unexpected token: splitArea.

I am trying to build a query where I can divide parcel 60-40% and in which 40% of the plot be subdivided into 3000sqm area and extrude building over it. Also I want to manage the orientation based on some angle (0-360 deg)

Can somebody help me with this. or suggest be best possible way to do this

Thank you

Re: SplitArea Function

DavidWasserman — Tue, 23 May 2017 22:41:47 GMT

Hi Abhishek,

Can you tell us your CE Version? Are you included all expected parameters?

Re: SplitArea Function

AbhishekSobbana — Wed, 24 May 2017 04:17:56 GMT

Hi David,

I am having City Engine V 2015.2 advanced License. I am new to CityEngine so I am following tutorial, I don't know what parameters are needed for the function to work. Please let me know if my version covers everything that is needed.

Thanks

Re: SplitArea Function

AbhishekSobbana — Thu, 25 May 2017 08:42:32 GMT

Hi all, While searching in the discussion forum, I found part of my answer of dividing the plot in direction to achieve the floor area for building which is 3000 sqm.

split(x) {50 : split(z){60:Extrude_Building}*}*}

also the rotation scope can be managed via,

rotateScope(0,Rotation,0)

but I am unable to randomize the split function, lets say my plot has to be divided in 33% of green cover and 27% of Openspace (which will also include setback from street and distance between the buildings) and rest 40% should be cover by buildings with 3000sqm foot print, and all this should also gives options so that when I regenerate the model I can choose which is better.

I tried using the percentage but somehow it is not working

Lot -->

35% : split(x) {50 : split(z){60:Extrude_Building}*}*
27% : OpenSpace
33% : Greencover
else : Extrude_Building

The above code provides just the one of the options but not all together.

Can anyone suggest how can I achieve this.

Thanks

Re: SplitArea Function

CherylLau — Thu, 25 May 2017 15:58:49 GMT

The splitArea() function is only available starting with 2016.0, but I would recommend upgrading to the latest, which is currently 2016.1.

With the splitArea() function, you can split a shape by percentage area.

splitArea Operation

For example, this split divides the area of the current geometry into 33% green space, 27% open space, and 40% building space:

splitArea(x) { '0.33: GreenSpace | '0.27: OpenSpace | ~1: BuildingSpace }‍

You can also split the current geometry according to an absolute area. For example, this split divides the area of the current geometry into one piece that has exactly 3000 sqm and one piece that has the remaining area.

splitArea(x) { 3000: BuildingSpace | ~1: OtherSpace }‍

Note that splitArea (and split) only splits the geometry in one direction. If you want to split in two directions (e.g. x and z), you'll have to do nested splits (as you figured out).

The reason why the percentages in the code you wrote don't work the way you expected is because the percentage syntax has a different meaning. It means that the rule will choose one of the cases with some probability, and that probability is defined by the percentage. So, if the rule is executed 100 times, it will choose to create ExtrudeBuilding approximately 35 times, and it will choose to create OpenSpace approximately 27 times.

Stochastic Rule

Re: SplitArea Function

deleted-user-Q-Ku9J1BlYDK — Thu, 25 May 2017 21:17:16 GMT

Hi Abhishek,

I second Cheryl on the version update. CLau-esristaff is that in the docs somewhere? I can't find it under the splitArea function.
David

Re: SplitArea Function

AbhishekSobbana — Fri, 26 May 2017 05:21:39 GMT

Hi Cheryl,

Thanks for your kind reply. Since I have CE 2015.2 can I upgrade my version with my current license?

Thank you for letting me know about the misinterpretation of stochastic rule, I was using that thinking of randomizing the placement of building, green space and open space.

When I use split(x) {'.33: OpenSpace | '.27: color("#FFC500") | '.4 : split(x) {50 : split(z){60:Building}*}*}

but this divides in one direction which gives me one option.

If we see block division parameter where we can see offset division where we can create courtyard division with openspace in the middle and buildings around it, similarly recursive subdivision we can give randomization of parcels.

My intention is creating the similar code where I can give this randomization or courtyard visualization for a parcel which I have in 5ac of plot. I think this function can be made without using block division parameter.

I hope this is understandable, Please let me know if there's a way where we can achieve this subdivision function.

Thanks

Ab.

Re: SplitArea Function

CherylLau — Mon, 29 May 2017 17:16:36 GMT

It's in the changelog. A link to it can be found at the bottom of the cga reference page.

CGA Changelog

Re: SplitArea Function

ThomasFuchs — Mon, 29 May 2017 17:29:53 GMT

CityEngine 2015.2 licenses won't work for CityEngine 2016.1
Go to https://my.esri.com to check if you have a license for 2016.1

If not, please contact your ESRI sales representative.

You can also test this version in a free trial: Esri CityEngine | Try CityEngine Free

Re: SplitArea Function

CherylLau — Mon, 29 May 2017 17:36:58 GMT

I don't understand your question, but I will make a guess that you want to split in two directions in order to partition a lot so that there is a courtyard in the middle.

Splits can only be made in one direction at a time (also applies to splitArea). To split a lot in two directions, you will have to perform two splits, one after another.

Alternatively, you can use offset, setback, shapeL, shapeU, and shapeO to create L, U, and O shapes. However, you cannot specify an exact area with these functions.

offset Operation

setback Operation

shapeL, shapeU, shapeO operations

Yes, you can apply recursion in cga to partition lots recursively. For example, if you apply shapeO to a lot, you can get a courtyard area in the middle. Then, you can apply the rule again to the courtyard, you can subdivide the courtyard into another shapeO (or whatever function you want), and you can keep subdividing resulting pieces until your desired stopping criteria.

Re: SplitArea Function

AbhishekSobbana — Tue, 30 May 2017 12:30:11 GMT

Sorry I confused you bit there,

I can not use splitArea since my version doesn't support that function, So I am using split function in both direction to achieve 33% Greenspace (GS), 27% Openspace (OS) and 40% Building (Bu), like the code below

split(x) {'.21: split(z) {'.21: OS | '.57: OS |~1: OS}
| '.57: split(z) {'.21: Bu | '.57: GS |~1: Bu}
| ~1: split(z) {'.21: Bu | '.57: Bu |~1: Bu}}

Bu--> shape : split(x) {50 : split(z){60:Footprint}*}*

As you see this one option that generates from the above code.

What I am trying to do is randomize between greenspace, openspace and building. Which is like this

The above I have achieved using the block parameter using recursive subdivision, but the issue in using this is we cant control the percentage we need for greenspace, openspace and building. One advantage I see is we can control the building footprint area say 3000 sqm and seed function where it control randomness between the plots.

Can this be achieved using split function and also using seed function where it control the randomness for plot by retaining the percentage breakup.

Re: SplitArea Function

CherylLau — Fri, 10 Dec 2021 23:31:54 GMT

Without splitArea() it is not really possible to divide a lot into a piece that is exactly 3000 sqm or end up with exactly 33% of the original area as green space. However, you might be able to achieve approximate results. Here are some ideas to explore:

* Recursion. You can recursively split your parcel until your desired stopping criteria. Maybe this criteria could involve the area or dimensions of the final lot? Maybe the split chosen at each level depends on the area or dimensions of the current lot?

* geometry.area(). This function will give you the area of the geometry. geometry Functions

* scope.sx, scope.sz. These will give you the size of the scope. If you have rectangular lots, this might be helpful in calculating how large of a split to perform in order to get a certain area. Of course, if you don't have rectangular lots, this calculation won't work. scope Shape Attribute

* Stochastic rules. If you divide a rectangular lot into equal sized cells (like a grid), then you can use a stochastic rule to make 33% of the lots green space and 27% of the lots open space and etc, for example. Stochastic Rule

* Reports. You can check how close you got to your goal by reporting the exact area.

report("Area.GreenSpace", geometry.area)
report("Area.OpenSpace", geometry.area)
report("Area.BuildingSpace", geometry.area)
‍‍‍

* Tutorial 11. In this tutorial, there is an attribute called greenspacePercentage. It doesn't divide the space exactly according to the percentage set in the attribute, but it is approximate. This can be seen in the reported values Area.Greenspace and Area.BuildUp. You can see how the approximation was made in the Lot rule where it chooses to be GreenSpace or a BuildingLot based on this greenspacePercentage. Tutorial 11: Reporting—CityEngine Tutorials | ArcGIS Desktop

Re: SplitArea Function

deleted-user-Q-Ku9J1BlYDK — Wed, 31 May 2017 02:18:53 GMT

Thanks Cheryl!

Re: SplitArea Function

AbhishekSobbana — Wed, 14 Jun 2017 12:50:09 GMT

Hi Cheryl,

Sorry I was offline for few weeks so was not able to reply.

Thanks for the details inputs you have provided, it has helped me to achieve my target upto 80%.

Currently to achieve this issue I have first divided the plot into smaller pieces using split(x) {50 : split(z){60:Footprint}*}* and then used

Lot --> case p(greenspacePercentage/100😞 report("Area.Greenspace",geometry.area) GreenSpace

else: report("Area.BuildUp",geometry.area) BuildingLot

which more or less provide me the percentage breakup for the for greenspace, building and openspace.

Thanks for navigating me to the tutorial.

I am still working on making rule for various subdivision of plots like it happens in default Block Parameter. where I can apply my percentage breakup.