Creating LOD 2 ~ 2.5 Buildings

Question

Hi, I'm trying to create a bunch of somewhat detailed buildings from footprints containing some GIS data (building height, roof height, basic roof shape, floors, etc), with as much CGA-scripting as possible. I'm not looking for a complete solution but any hints or tips would be very helpful 🙂 The modelling includes: * Extruding the buildings * Texturing each facade with a seperate texture * Extruding significant attributes (like a balcony) and texturing them * Roof modelling, again with attributes extruded and textured * (The objects should obviously retain the GIS data) I've experimented a bit and can create the basic building shapes and texture them if they're simple blocks (comp front, back, sides). However, I can't really figure out a good way how to continue. There's always the option to do a shape conversion and extrude/texture manually, but I'm rather hesitant to use it because it feels too stiff and "final". My main problems are: * Texturing buildings with an arbitrary number of sides. I tried comp(f){all:SubShapes} but after that I'm kinda stuck. I'd like to do a loop like "for i = 1 to apply texture from ". Is that possible? * Accessing the generated sides for attribute extrusion & texturing without converting them to shapes. I hoped the inspector would give me a some info about the sides but nada. I figured I could import a building-specific script after running the above one, but again I haven't got the slightest clue how I could specify what to extrude at which point (except manually, which I'd like to avoid). * Creating a more complex shape from a footprint, like placing a smaller roof on a bigger roof, or stairs-like structures (again with textures). Any ideas where I should start to look?

MatthiasBuehler1 · Answer

Hi !

Concerning the brightness :
Could it be the lighting/shading in your scene ?
The light type ? ( toggle it by using the 'L' key.)

Yes, you can place objects on top of your roof. You have to create an 'asset', then insert it on the top shape of your initial geometry.

Did you already see the intro tutorial videos here ? ->
http://forums.arcgis.com/threads/64843-CityEngine-Collection-RESOURCES-FAQ-HELP

MatthiasBuehler1 · Answer

hi !

you can make a 'loop' by using the 'comp.index'.

so after comp(f) {side: Facade}

just print the component split's index :Facade -->
    print (comp.index)

use this index for your texturing by catenating strings.

e.g.Facade -->
    print (comp.index)
    texture("assets/myTex_" + str(comp.index) + ".jpg")

Of course, you need to setup the UVs first.

Hope this makes sense.

JoanneO_Brien · Answer

Hi

I'm not sure about creating a loop, if there is one which has a majority then you could just use that in the else section. Also you can say: case facadeIndex == 1 && facadeIndex == 1 etc : Wall1
else : Wall2

The && function allows you to use more than one indexside. 
Alternatively you could try  creating your conditional rule within a split prehaps and using the asterix * to denote repeat? Not sure if that'd work though.

In order to get the building texture across the whole building you need to add the texture before you split it up. It's all a matter of where it comes within the rulefile.

I'm not 100% sure about the structure ontop of the building but you insert it as an obj file to appear on the roof ( create it either within sketch and export or create using the polygonal shape tool and export as obj).

Also for extruding stairs, rather than looking for coordinates, you want them attached to a building don't you? so when you create your splits just insert the stairs into one of the groundfloor splits for example this is how I did mine:
@Group ("Steps")
attr stepHeight = 0.19
Group ("Steps")
attr stepDepth = 0.27

Base--> split(x) { ~1 : BaseSide | doorWidth : split(y) {~stepHeight : Step(split.total - split.index)}*  | minWallWidth  : BaseSide}
       
Step(index) -->
 extrude(stepDepth * index)
 setupProjection(0, scope.xy, 2, 2)
 projectUV(0)
 texture(step_tex)

that was so that I could have steps under my doors.

hope that's of some help!

regards

Joanne