Unreal Engine (Datasmith) Export

Format Description

The Unreal Engine (Datasmith) exporter provides simple data transfer from CityEngine into the Unreal Engine Editor. The main purpose of this exporter is for architectural and design visualization workflows, but will obviously also work for games and other tasks.

To import a CityEngine scene into the Unreal Editor, it is recommended to use the "CityEngine Template Project for Unreal" which is available at the Epic Marketplace (simply search for "CityEngine"). This template contains master materials with shading networks that automatically connect CityEngine material attributes to Unreal materials (see Materials).

Specific Export Options for Unreal

Unreal has no additional export options (see general export options).

Mapping between CityEngine and Unreal entities


Exported geometry is combined per initial shape (e.g. a building) and by materials. Instanced geometry is reused in Unreal. Each exported shape is represented as an Actor in Unreal. Each unique mesh is exported as a Static Mesh and reused if possible.


Materials are translated to Unreal by passing CGA material attributes to an Unreal material instance which is based on a certain master (or parent) material (see Instanced Materials).

By default, an opaque master material is used (see Default Master Materials). A custom master material can be assigned by setting the material.shader CGA attribute to the corresponding Unreal material path, e.g. /Game/Materials/CityEngineMaterials/M_CE_MyMaterial.

Each CGA material attribute is exported and can be accessed in Unreal by using a material parameter with a specific name and data type. The following is a table with the CGA material attributes and their respective Unreal parameter name and type:

CGA attribute Unreal Parameter Name Unreal Type Note
Color Vector3
Opacity float
Reflectivity float
Shininess float
BumpValue float
Ambient Vector3
Specular Vector3
ColorMap Texture2D
DirtMap Texture2D
SpecularMap Texture2D
OpacityMap Texture2D
OpacitySource float For OpacitySource value:
0: Use color channels (gray level) from OpacityMap
1: Use alpha channel from OpacityMap
BumpMap Texture2D
NormalMap Texture2D

Default Master Materials

The CityEngine template scene provides several master materials. By default the M_CE_Opaque material is selected which is used for opaque materials. Other master materials for transparent and masked materials exist. Further documentation on the default materials can be found in the CityEngine template project in the Unreal Marketplace.

The Unreal Engine sorts transparency per actor. Exporting overlapping transparent actors will lead to rendering artifacts. Masked binary opacity is not affected by this limitation.

Default Material Attribute Translation

The default master materials translate the CGA material attributes roughly to a physically based Unreal Material.

The specular color is not used in Unreal. The specular color in Unreal depends on the base color and how metallic the material is.

CityEngine reflectivity and shininess are translated to Unreal Roughness and Metallic.

Further Reading

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