how to add seed function

Question

I have split a parcel into pieces and assigned a probability function between  building, greenspace and openspace.

I have also given rand height function for the building.

When I regenerate(ctrl+shift+g) it give me options like,

But the issue is once I select the building footprint location I want to regenerate for random height , when I try to that it will change the building location also because of probability function.

I there a way, where I can apply seedian function just for height without changing the location of the building. something like this

Thanks

Ab

CherylLau · Answer

Handles only work on attributes. In order to use handles, you would have to redesign the code so that you have attributes for the quantities that you want to have handles for. For example, you could put a handle on the attribute nFloors and then set the handle to use the shape which is the mass of the building which is extruded to the correct height. As for the seedian, again, I don't think setting it will get you what you want, but maybe you see a way of getting it to work for you. You can set it in cga code using set(). set Operation This sets the seedian to the value 123456, for example. set(seedian, 123456)‍‍

AbhishekSobbana1 · Answer

Thanks for the Tutorial, helped me a lot to understand more ways to write my code.

But I am not sure how to put a handle in my code since it is generated from

GFHeight + nFloors*UFHeight

Here is my complete code

Lot -->
    split(x) { Width: Col(split.index, split.total)}*

Col(col_ind, nCols) -->
    split(z) { Length: Cell(split.index, split.total, col_ind, nCols)}*

Cell(row_ind, nRows, col_ind, nCols) -->

extrude(getHeight(row_ind, nRows, col_ind, nCols) )

//////////////////////////

getHeight(row_ind, nRows, col_ind, nCols) = GfHeight + nFloors(row_ind, nRows, col_ind, nCols)*UfHeight

nFloors(row_ind, nRows, col_ind, nCols) = 
   case Variation_Mode == "None" || (nRows*nCols) < 2 : Floor_Max 
   case Variation_Mode == "Increasing" : (Floor_Min) + (rint((Floor_Max-Floor_Min)*((row_ind*nCols+col_ind)/((nRows*nCols)-1))))
   case Variation_Mode == "Decreasing" : Floor_Min + rint((Floor_Max-Floor_Min)*(1-(row_ind*nCols+col_ind)/((nRows*nCols)-1)))
   case Variation_Mode == "Alternating" : Floor_Min + rint((Floor_Max-Floor_Min)*((row_ind*nCols+col_ind)%2))
   else : rint(rand(Floor_Min-0.49,Floor_Max+0.49))     //////////// Random Height Function

I can't put handle on both GFHeight and UFHeight in the attribute because both will be constant from the attribute.

I saw the seedian shape attribute in help link but didn't get it properly how to apply in the code. It will be great if you can provide some example on using "seedian shape attribute"

Thanks

CherylLau · Answer

Handles were first introduced in 2015.0, but they have been updated and extended since then.  Here is a tutorial on handles and some pages from the help doc:

Tutorial 18: Handles—CityEngine Tutorials | ArcGIS Desktop

Handles

Creating Handles

Handles are only available on attributes.

The seed is not really a function but rather a number that belongs to the shape.  In cga code, you can get and set this number using the seedian shape attribute.

seedian Shape Attribute