topic Re: Exponentially changing attribute in a function in CGA rule in ArcGIS CityEngine Questions

Exponentially changing attribute in a function in CGA rule

GeorgiosAnastasiou — Tue, 05 Jul 2016 16:38:57 GMT

In a CGA rule I have a repeating function that needs to be changing the set attribute value exponentially and not proportionally as I have it now. One way to do it could be by setting an attribute inside the function (like in python), but it is not supported. What would be a way of doing that?

Re: Exponentially changing attribute in a function in CGA rule

GeorgiosAnastasiou — Tue, 05 Jul 2016 16:52:48 GMT

for example in this case, you can apply it in any footprint and see the shape:

attr Factor = 0.97

attr Depth = 0.01

attr Stop = 0.1

Lot-->

extrude(Depth)

center(xyz)

comp(f) {top : Levels}

Levels-->

case(scope.sx > Stop) :

s('Factor, 'Factor, 0)

center(xy)

extrude(Depth-0.02)

comp(f){top : Levels}

else:

NIL

The target is in each repetition the attribute "Factor" to be smaller than the previous one. So, the higher the floor, the smaller the size becomes exponentially.

Edit: it should work as I want it with

attr Depth = 0.1

Re: Exponentially changing attribute in a function in CGA rule

LR — Sat, 11 Dec 2021 18:42:57 GMT

You mean something like this?

attr RowRow = 2
attr Expo = 2
attr HoldMe = 0

Lot -->
extrude(5)
color (1,1,0)
print("----------")
DoTheThing

DoTheThing -->
case Expo > 10: EndThis
else: GoGo

GoGo -->
print("Expo old: " + Expo)
set(HoldMe,pow(RowRow, Expo))
set(Expo, Expo+1)
print("Expo new: " + Expo)
print("Exponential!: " + HoldMe)
print("--")
DoTheThing

EndThis -->
#important
print(":D-/-<")
print(":D-\\-<")
print(":D-/-<")
print(":D-\\-<")
print(":D-/-<")
print(":D-\\-<")
print(":D-/-<")
print(":D-\\-<")

Re: Exponentially changing attribute in a function in CGA rule

GeorgiosAnastasiou — Thu, 07 Jul 2016 15:01:01 GMT

That was very useful, and by following the log in CGA console I understood exactly how it works.

I found exactly what I needed: the "set" operation to change the attribute inside the function, and the exponential growth of the value, in this case by using the "pow" (power) operation.

Thank you very much Z R!