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Rules

NicoleHanson

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

MatthiasBuehler1

Hi !

Are you using and altering an existing rule set ? E.g. the Modern Street rules ?

If so, maybe you simply have set the wrong Start Rule, where it is already clear that only 1 land is created.

It not and you're creating your own rules, make sure you have a repetitive split in the right direction (u or v texture coordinate direction) which creates the lanes.

split(v, unitSpace) {~laneWidth : Lane. }*

Let me know if this helps.

Matt

NicoleHanson

Hi Matt!

I'm using an existing rule: Street Construction - that came with the 3D City Creation data download.

I'm not familar with programming, so I'm not even sure where to start with creating my own. Is there a tutorial?

Thanks!

NicoleHanson

# create left and right side of the street (per default same nbr of lanes in both directions, but user can influence it via attributes)
Streetsides -->
 case calcNbrOfLanes < 1.1 : Asphalt
 case Nbr_of_left_lanes == 0 && Nbr_of_right_lanes == 0:
  split(v,unitSpace,0){ ~calcLanesLeft    : Lanes(calcNbrOfLanes,connectionEnd,0) Vehicles(0)
       | Median_width      : Median
       | ~calcLanesRight   : scaleUV(0,-1,-1) Lanes(calcNbrOfLanes,connectionStart,2) Vehicles(2) }
 else:
  split(v,unitSpace,0){ ~Nbr_of_left_lanes : Lanes(Nbr_of_left_lanes,connectionEnd,0) Vehicles(0)
       | Median_width      : Median
       | ~Nbr_of_right_lanes : scaleUV(0,-1,-1) Lanes(Nbr_of_right_lanes,connectionStart,2) Vehicles(2) }

Here's what I have for the lanes. Would I change the Vehicles to 1 instead of 2?

MatthiasBuehler1

Hi !

Hmm. Can you also post a screenshot (please also of the navigator, so I can see the Start Rule and the attributes you have set) ? I'm not perfectly sure if I understood correctly what you meant in your first post.

You have only 1 textured lane but 2 lanes of cars, it that right ?

Let me know..

Matt

NicoleHanson

Hi !

You have only 1 textured lane but 2 lanes of cars, it that right ?

Let me know..

Matt

Yes, that's correct.
[ATTACH=CONFIG]21161[/ATTACH]

And now I have some cars perpendicular to the road.

twolanesofcars.jpg

MatthiasBuehler1

Hi !

If you have edited Vehicle() in your code, cars will be rotated because that drives their orientation.

I know editing somebody else's code, especially if it's that complex..

It seems the code was not created to support all possible scenarios. For this example, I guess I cannot just quickly fix it either.

Maybe you'd be interested in starting a new rule which does what you want ?
I could help you a little with it and you'd learn a lot about CGA ! 🙂

[I usually start fresh if other people's code is too complex for me to understand.]

Let me know ..

Matt

NicoleHanson

If you'll help me, sure! Let's start fresh.

What do I need to do first?!

MatthiasBuehler1

First ..

What controls do you need ?
What elements you want to have on your streets ?

Number of Left Lanes / Right Lanes ?
Median on/off ?
..

NicoleHanson

First ..

What controls do you need ?
What elements you want to have on your streets ?

Number of Left Lanes / Right Lanes ?
Median on/off ?
..

I want to have both cement and asphalt. Yellow lines and dashed white lines. I need 3 Right Lanes, 3 Left Lanes. But also, need it to be able to vary, as I need 2 for both, and 1. As I have a split highway with on/off ramps, and local roads.
Median on for part of it, but also off for some of it.
Also, to be able to populate cars, with changing frequency. And I need to be able to animate it (so that I can show the public what will happen at a specific interchange).

I figure I can wait a little bit before adding buildings. Right now I want to be sure that I can get a working model of the roads.

Thanks Matt!

MatthiasBuehler1

Can you post a few representative images too ?

I'll have to think about this then .. 🙂

NicoleHanson

So here are some examples of what I'm looking to model. [ATTACH=CONFIG]21314[/ATTACH][ATTACH=CONFIG]21315[/ATTACH][ATTACH=CONFIG]21316[/ATTACH][ATTACH=CONFIG]21317[/ATTACH]

Hi !

Here's a start.

Read it carefully and try to understand every little step.

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

streetRule.zip

NicoleHanson

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 !

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 ? 🙂

NicoleHanson

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 !

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.

NicoleHanson

Yes! That helps a lot! Thank you!

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.

NicoleHanson

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 !

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.

NicoleHanson

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

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.

NicoleHanson

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

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 :
    ..

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.

NicoleHanson

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

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

NicoleHanson

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 ..

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

NicoleHanson

[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!

Capture.JPG

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