Hi Jake,
CityEngine (as your I’m sure aware) exports to many different 3D formats that are compatible with Unity3D. This would best be served with the FBX format however both OBJ and DAE (Collada) will also import directly to Unity3D. There is a distinct difference between CityEngine and Unity 3D file format interoperability and the implementation of the SDK inside of Unity to apply CGA rules.
Some key points to remember when going from CityEngine to Unity :
· Real-world Terrain / Imagery needs to be tiled for highest resolution 4000dpi max resolution in Unity.
· Unity recognizes files in centimeters but in CityEngine we use meters. Once the files are imported to Unity, the scale factor on the FBX can be changed before adding it to the scene.
· Keep X,Y, Z center values the same on export in order to have all exported layers with the same spatial reference. This can also be set to center on your selected model in CityEngine
· Create doorways in CGA Rule in order to apply collision mesh to only the outside of the building, this will allow entry to the building.
· A slight 10cm offset might be needed in order to reduce the shape clash between street polygons and the terrain mesh.
· If LOD (level of detail) is set up in a rule then separate LODs can be exported and then merged into an LOD group in Unity. This will allow control over the detail as it relates to player location.
· In order to export all models (regardless of layers) as one FBX file from CityEngine, it will be important to set up the naming scheme inside the rule itself. This highlighted example from below will then name all corresponding generated models correctly in Unity when the “merge meshes by material” is selected on export from CityEngine. In the case below we were able to string together object attributes which could be anything.
CityEngine rule snippet:
Texture -->
setupProjection(0, scope.xz, Scale_X, Scale_Z)
texture ("assets/Image_Textures/" + layerName + ".png")
projectUV (0)
rotateUV (0, Rotate_Angle)
....
set(material.name, layerName + "_" + "string" + moreattributes)
A good FBX tutorial can be found here as well: How to Import CityEngine Scene into Unity3D Tutorial | 3Decide
