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Rules

I think there's a step in my rule somewhere that doesn't take into account the number of lanes I have. On one stretch of road, it's one lane going in one direction. But I have two lanes of cars after applying the rule. Any idea where I can find out how to get this fixed?

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Accepted answers

MatthiasBuehler1

Hi !

You need to distinguish between 2 things :

1] The GUI creates streets and shapes ( I usually call this phase 'shape creation' ). That's done either manually or via Python.

2] CGA starts on a given, existing shape with attribute evaluation and model generation.

Phase 2 comes after phase 1. This also means that CGA can NOT alter the state of things that change shapes.

Thus, your things need and can be done with Python.

Make sense ?

Matt

All comments

Yes! Thank you!

MatthiasBuehler1

Hi !

You need to distinguish between 2 things :

1] The GUI creates streets and shapes ( I usually call this phase 'shape creation' ). That's done either manually or via Python.

2] CGA starts on a given, existing shape with attribute evaluation and model generation.

Phase 2 comes after phase 1. This also means that CGA can NOT alter the state of things that change shapes.

Thus, your things need and can be done with Python.

Make sense ?

Matt

Hi there!

Is there a way to use a CGA rule to change the attribute width of the sidewalks and streets? The only way I know how is through the user panel in the inspector. I would like to be able to select all streets and then drag/drop a rule. Is this possible?

Thanks!

MatthiasBuehler1

And the rule ..

NewStreetRule.zip

MatthiasBuehler1

Here's the vid :

https://www.youtube.com/watch?v=6QuaX7GBsDg

Thank you Matt!

MatthiasBuehler1

Hey Nicole ..

I've created a video which talks about the whole code here. I'm working on having the video file published here in this thread so you can watch it..

May take some more time ..

OK sweet!! Thanks again for all your help!! Now to see if I can get the animation going right. I downloaded the trial of that software you mentioned earlier.

MatthiasBuehler1

Hi,

Yeah. You set the rule files, you set the start rules and then generate the models.

So as long as you have the Start Rule defined within the assigned Rule File, you can create the resulting geometry.

So e.g. you can create Streets with a Street Rule File and Sidewalks with a Sidewalk Rule File or completely different define all Start Rules within one big myCity.cga Rule File which is assigned to all Shapes, such as e.g. in the Paris Example.

Note that I always code with colors in CGA, which shows me what I'm doing. I'd say you should do the same.

Note too that I created the curved streets with the Edit Street Tool. Hit the 'c' key when you have a street graph selected, then edit the street in the viewport. Add more subdivisions to make it smoother with the precision attribute in the Inspector.

m.

I understand. Those three were roads. When I have a line, and the create streets, I can add attributes to create a sidewalk as part of that right?

MatthiasBuehler1

Cool to hear ..

But make sure that on the Sidewalk Shapes you don't set the StartRule to be Street too !

Notice if you draw a Street that the shapes produced have the Start Rule ( in the Inspector) :
- Street
- Sidewalk

I've JUST been talking about what happens on the Street Shapes, nothing about the Sidewalk. Ok ? If you assign the StartRule 'Street' also to the Shapes which were Sidewalk shapes, you're triggering again new Street Models on those.

Ok ?

[ATTACH=CONFIG]21829[/ATTACH]This is what I got. Not quite the same as the picture you had. But it's making sense now! Slowly, but it is!

MatthiasBuehler1

Hi ..

These 3 examples ( StartRules Street1, Street2, Street3 ) should show what the ideas are behind the splitting strategies.

Run the code and check what the code produces. See the image attached.

[ATTACH=CONFIG]21828[/ATTACH]


attr width_1 = 5

Street1 -->
 split(v,unitSpace,0){width_1 : Red | ~1 : Green}



attr myLaneWidth = 3

Street2 -->
 split(v,unitSpace,0){width_1 : Red | ~1 : RestShape}

RestShape -->
 split(v,unitSpace,0){~myLaneWidth : Green }*


attr medianWidth = 1

Street3 -->
 split(v,unitSpace,0){~1 : MultiLane | medianWidth : Green | ~1 : MultiLane}

MultiLane -->
 split(v,unitSpace,0){~myLaneWidth : Red }*


Red -->
 color(1,0,0)

Green -->
 color(0,1,

streetShapes.jpg

I think so.

So after I set the split () {~...}*, I then can have a line that has the offset, or a line of code that has the one ways for those areas that are not evenly split on lanes?

Also, when I'm seeting my Median function, for the color can I use one of the textures in my assets folder? ex: color (Shoulder_tex) where Shoulder_tex is defined from the assets?

MatthiasBuehler1

Hi !

[ATTACH=CONFIG]21781[/ATTACH]

In the image you see the streetWidth street parameter which defines the width of the street shape.

So in your case, you would set this value to ( 2 + 2 ) * 3m = 12m first.

Then you use CGA to split into the amount of lanes which result ( 2+2 ).

This workflow is set because you must set the streetwidth in the first place to even get the street shapes.

A little additional detail which may help you :
split() {~ .. }* splits into even parts. The little star symbolizes a 'repetitive' split. The tilde (~) sign evens out the dimensions. That means the combination makes the split result in a full number of lanes for each side, no matter how wide the street is.

ok ?

m.

streetWidth.jpg

and note :

the 'Model' is created based on the 'Shape'.

So a street graph defined the width of the total street shape. So since the total width is already give plus using the fact that 1 lane is about 3 meters wide, n lanes can actually be created.

e.g. a 9 meter wide shape can produce 3 lanes.

so that can be 1 left lane and 2 right lanes. But since the total width of the street is given and thus drives the total number of lanes, it makes 'no sense' to define
attr Lanes_Left = 2
attr Lanes_Right = 2
makes sense ?

the laneOffset I have in my code then defines the offset :

e.g. if 5 lanes can be produced, 2 left and 3 right can be produced. an offset of 1 makes 1 left and 4 right lanes.

makes sense too ?

m.

No, it doesn't make sense. Most of the roads I will be modeling are 2 and 2. Except for the interstate which is one way, but goes from 2 - 4 lanes.

I would have to enter the total width then to accomidate for that, if I do it how the sample code is, right?

MatthiasBuehler1

and note :

the 'Model' is created based on the 'Shape'.

So a street graph defined the width of the total street shape. So since the total width is already give plus using the fact that 1 lane is about 3 meters wide, n lanes can actually be created.

e.g. a 9 meter wide shape can produce 3 lanes.

so that can be 1 left lane and 2 right lanes. But since the total width of the street is given and thus drives the total number of lanes, it makes 'no sense' to define

attr Lanes_Left = 2
attr Lanes_Right = 2

makes sense ?

the laneOffset I have in my code then defines the offset :

e.g. if 5 lanes can be produced, 2 left and 3 right can be produced. an offset of 1 makes 1 left and 4 right lanes.

makes sense too ?

m.

MatthiasBuehler1

btw. use the TEXT editor to author the rules.

if a median is done or not .. for that I'd make a 'boolean' attr.

I've done this in my example code :

attr doMedian = true

yes, you can use copy paste, but only if the code works. you'll get errors otherwise.

using ctrl-f, you can search your code. search my code for all places, where 'doMedian' is used.

Note the case :

case doMedian :
    ..
else :
    ..

I'm getting there! Can I cut and paste different lines from other rules?

OK, so I've made a list of attributes, that I know I want right now. Some of the roads don't have a median, so how would the fuction look for that. Would it be the case, else (if, than) statements?

Also, with having a shoulder, do I need to designate left and right on that, like I do with the lanes?

Here's what my attributes look like so far:

## Attributes

attr Lanes_Left = 2
attr Lanes_Right = 2
attr Lane_Width = 3.5
attr Shoulder_Width = 3
attr Median_Width = 1.5

MatthiasBuehler1

It all boils down to some statistical math where you calculate how many car objects you place on the lanes.

Quite easy to calculate if you already have the numbers ..

The person who did the Modern Streets Example just set up the function so that he can enter the 'traffic density' basically.

Btw. you should re-code the whole thing from scratch to get a hang of it. 🙂

We can then later on also place cars with your numbers.

M.

I'm starting to understand more of the code. I've also been looking at other example codes from the tutorials.

Thanks so much for helping me!

Oh, another question. When entering the number of vehicles per km, what if I have numbers for the number traveled per mile, but it's the average daily totals?

MatthiasBuehler1

Hi !

that would be the next step in the rule at the current state.

e.g.
placing cars would use an other UV-split to cut a thin line on which cars. same can then be done with sidewalks to distribute trees or street furniture.

if you have point features in ArcGIS, you'd just insert assets via on these positions via i() in CGA.

makes sense ?

let me know when you understood most of the code, then we can add some more details to it.

m.

Ok, got another question, but I wasn't sure if I should start another thread or not...

Once I have my streets how I like them, how do I add points/polygons to show where the street furniture are? Mainly, traffic lights and lamps? Would I just create another shapefile in ArcMap, and then import it into CE, then apply the rules for them?

MatthiasBuehler1

Hi !

Ok, cool.

So go through the code and play around with it, together with curved Street Shapes.

If you have more questions so far, let me know ..

m.

Yes! That helps a lot! Thank you!

MatthiasBuehler1

Hi !

It all just looks more complex than it actually is.

Let's go through it step by step in the CGA code :

1]
We want to create a Street model from Street shapes. So we use a CGA rule to split that shape and colorize it until it represents a street how you need it.

2]
For now, we only work on Street Shapes, so we NIL Crossing and Sidewalk Shapes in the CGA code. This means no Model is generated.

3]
We define a series of attributes we can use :
- laneOffset : With the offset, we can shift the lanes sideways e.g. 2 left and 3 right can become 1 left and 4 right.
- laneWidth : Width of a street lane in meters (3 meters.. code in meters !! )
- medianWidth : 0.1 meter
- oneWay : @Range ("no", "left", "right") . the attr oneWay gets specified better with that 'annitation'. This makes that you have the 3 options as a dropdown in the Inspector for this attribute.
- doMedian: true or false. This is a 'boolean' value which is either true or false. Depending on it's state, a median will be made or not.

4]
functions : functions are there to calculate some values and return a value.
e.g.
f = 5

if f is called, the value of 5 is returned. In print ( f ), 5 will be printed.

5]
- rint() means round integer. this rounds up or down to the next full integer number. 5.1 will be rounded to 5.
- geometry.dv(0,unitSpace) is the width of a curved street, in meters.

6]
attrs with the @Hidden annotations are not displayed in the Inspector. We use them hidden as 'generic attributes' to pass values down our rules, thus they are set at the very beginning, after Street -->

7]
case : .. else : is the same as an 'if statement' in other programming languages. this tests if something is true or not.

to TEST if something is true or not, the '==' (double equal sign) is used.

E.g.
5 == 5 is 'true' in real world, so we try to create similar statements in CGA to split our geometries.

8]
In the rule called 'DoStreet', we then distinguish the different cases and split the street geometries among the U and V dimension. Those are actually texture coordinates. This is a good trick, because Street Shapes already have proper UV coordinates. The V direction is along the WIDTH of the street.

9]
So in general, with the functions, what we basically do is find out the proper number of possible lanes in each direction, with or without a median and then split the geometries accordingly.

Let me know if this short input helps you a little further...

I know it's complicated at the beginning. But once you know what's happening, the magic becomes easy ! 🙂

m.

OK, so I think I've watched that tutorial a couple of times now...

But it still didn't really answer how to know what CGA programming codes/words to use: ie attr, case...

It also didn't talk about knowing the color codes.

Also, I'm not sure what the @ in front of some words means.

And on the functions, how do you even know what it is?

MatthiasBuehler1

Hi !

No problem .. 🙂

The units are in meters .. always in CGA ( CGA is CityEngine's scripting language which creates the geometries ).

The '-->' is the definition of a CGA 'rule'.

The best intro into CGA you get with my tutorial video 6...
http://video.arcgis.com/watch/1772/tutorial-6-basic-shape-grammar

It may explain most questions you have right now at the beginning, then we can cover more questions until all is clear ..

ok ? 🙂

OK, I have a lot of questions, and I barely got to the functions line...

First off - how do I know what language (like knowing what to use: attr, case, else, etc)?

How do I know what values to use for default, are they real world, or a scaled down? For example the lanes on the roads are 12ft, but for the attr laneWidth it's 3.

Does it matter what the attributes are called?

Is there a book or something that would have the programming language, like the functions, or knowing how to set it up? It looks so different than python (well the little bit I know about python).

Oh, and what does the --> mean?

And how do you know what values to do for the color scheme?

I do know that there's a list of attributes, which I think is the parts that can vary for the imput.

Sorry!! And Thanks for your help!! I'm going to look it over again, but those are the questions I have so far.

Nicole

MatthiasBuehler1

Hi !

Here's a start.

Read it carefully and try to understand every little step.

Let me know if there's questions so far .. 😮

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