Model export application notes

Note #1: Format Recommendations

Format recommendations for various software and functionality are listed in the table below.

Note:

Some of the software and functionality listed require additional plug-ins to load all formats.

Software or functionality	Format	Required options
ArcGIS Earth	KML
Autodesk Max	OBJ, FBX	For obj, enable import of smoothing groups in Max.
Autodesk Maya	FBX, ABC, OBJ	(ABC materials cannot be imported out of the box in Maya.)
Autodesk MotionBuilder	OBJ, FBX
Blender	OBJ, FBX, ABC	Multitexturing
Cinema 4D	OBJ, DAE	Multitexturing
Deep Exploration	OBJ, FBX, DAE
SideFX Houdini	ABC, USD
Foundry Katana	ABC, USD
Lightwave	OBJ
Polytrans	OBJ, FBX, DAE
e-on VUE	VOB, OBJ

Note #2: Working with Expensive Assets

If you work with large assets, you can create simplified proxy assets and switch between them with a global level of detail (LOD) attribute. To avoid scattering the LOD attribute over the rules, you can put the conditions into separate asset loader rules, as shown in the following sample code:

attr LOD = 0
...
Shaft -->
    s(diameter,’1,diameter) center(xz) color(shaftC) ShaftAsset 
    
ShaftAsset -->
	    case LOD == 0: primitiveCube()
	    else: i("path/to/expensive/asset.obj")
...

Note #3: Working with Large Models

To create large models, implement global CGA attributes into the rule sets so you can selectively block the generation of polygon-intensive model features. For example, you can replace high-polygon Greek columns with simple cuboids using an attribute LOD together with a corresponding condition in the CGA rules.

Application example

To render a large scene with Maya or Arnold when you have a CityEngine scene with an LOD switch, export the scene with LOD = 0 to a single .obj file (without textures) and import it. For example, if you import it into Maya, you can quickly set up the lights and camera without using heavy geometry. Once the environment is ready, you can go back to CityEngine and export the scene with LOD = 1 to USD format files and link them to the render setup.

Implementation example

An example of a modified version of the Parthenon temple shape grammar is shown below. The LOD attribute is used.

The temple with LOD = Low, or ~90k polygons ... # ---------------------- model parameters ---------------------- @Group("Model Options", 0) @Order(1) @Enum("High","Low") attr Level_of_Detail = "Low" const HighLOD = Level_of_Detail == "High" ... ### Columns ### ... ColumnTile --> set(trim.vertical,false) primitiveCube() s( Diameter ,’1, Diameter ) t(’-0.5,0,’-0.5) color(Column_Color) [ case HighLOD : Column else : Column. ] Column --> ... ...

The temple with LOD = High, or ~675k polygons