As I mentioned in a previous post, the Planning – 3D Transect example (available through CityEngine by going to Help > Download Tutorials and Examples) is one of the most useful resources I’ve come across, particularly since my first “for real” project is not a city center, but a public sports complex on rural land with few buildings and lots of terrain, trees and grass. To get an idea of how this natural look was generated, I’ve been taking inventory of the assets, rules and other resources in the Transect project folders. Look at the file structure and you’ll get a good idea of what is available.
- The assets folder includes texture files for buildings, landscapes and streets plus some “low polygon” 3D models.
- The rules folder contains cga files for creating and parameterizing buildings, landscapes, streets and placing trees.
- In the folders Buildings_Advanced_Buildings and Landscape_Design_Greenspace, there are master “construction” rules for each, Building Construction.cga and Greenspace Construction.cga. I’m not real keen on there being spaces in the rule file names, even though CityEngine will process them this way.
- The Support sub-folders contain all of the rule files referenced in the master rules. If you’re a programmer and familiar with “includes” (or in this case, “imports”) you’ll know what these are. It is a lot easier to edit and troubleshoot code divided into blocks than have all-lll of your code on one huge, long scrolling page,
In the “assets” folder, items in the LowPolygon3D.com sub-folder need some explanation. 3D models, like the model of the cyclist below, are created from networks of nodes and edges. In this case, three files are needed to do the job, each with the name bicycle_female_1.xxx:
- bicycle_female_1.obj, an object file (illustration left) draws the nodes and vertices;
- bicycle_female_1.jpg, an image file (center) has image patches to texture the surfaces;
- bicycle_female_1.mtl, a Material Library file (right), is a simple ascii text file that defines materials, colors, textures and reflection maps for the model.
There are also a number of .cgb (CGa-Binary) files within the “bin” (binary) folder. According to ESRI documentation, the CGA rule files in your models are run through a compiler built-in to CityEngine; they are translated to computer language and run so you can navigate a 3D model on your desktop. The compiler converts CGA to CGB. Therefore the other .cgb files you see can be run without having to go through the compiler.