Terrain Layer

The Terrain Layer is a special map layer that visualizes the elevation of the scene topography using image data. It also serves as reference elevation for align operations for scene objects such as shapes or graph nodes.

Creating a Terrain Layer

A terrain layer can be created in the following ways:

  1. An image is dragged from the Navigator into the scene
  2. A Terrain is imported with File → Import... → Terrain Import
  3. A new Terrain layer is created with Layer → New Map Layer... → Terrain

These actions trigger the Terrain Dialog

 

Terrain Dialog


 

Heightmap File: Choose an image from your workspace which will be used as heightmap mesh / Digital Elevation Model. Normally this is a greyscale image. When a georeferenced image is selected, elevation and bounds are set automatically.

Texture File: Choose an image from your workspace which will be used to texture the heightmap mesh. Normally this is a greyscale image. When a georeferenced image is selected, elevation and bounds are set automatically.

The texture file is applied over the exact extent of the heightmap mesh. It is therefore crucial that your texture file has the same extent as the heightmap file.


Channel: Choose the source channel from the image that is used to read the data for the elevation. For most images brightness is the best choice.

Min. elevation: The minimum value / the lower bound for the elevation in meters. For specific images this value is read automatically from the file.

Max. elevation: The maximum value / the upper bound for the elevation in meters. For specific images this value is read automatically from the file.

Bounds SIze: The Width and Height of the resulting terrain in meters. When a georeferenced image is selected, this value is set automatically.

Bounds Offset: The location of the resulting terrain in meters. When a georeferenced image is selected, this value is set automatically.
Note that the button left of X-Offset can be used to change the reference point for the terrain's position.

16-bit and 32-bit images are supported for heightmap files. The 16/32-bit range is scaled to the elevation bounds similar as it is done with standard images.

Due to the fact that the images displayed in CityEngine all need to fit in the graphics card memory, it is highly recommended to use as small images as possible. CityEngine will restrict resolutions to a max of 4000x4000 pixels per image.

 

Terrain Layer in CityEngine scene

The new terrain is added as a new layer in the scene editor. If the terrain is not visible in the 3D viewport, right-click on the terrain layer and choose Frame Layer.

Terrain layers (like all map layers) can not be selected in the 3D viewport directly, but only via scene editor.


A terrain layer in the Scene Editor


Terrain with wireframe alpha enabled

Setting terrain parameters in the Inspector

To change the parameters of a Terrain, select the terrain layer in the scene editor, and look for its parameters in the Inspector.

Map Layer attributes


The map layer attributes of a terrain layer in the inspector.

Attribute Function
Name Layer name
Visible Layer visibility
Color Color value multiplied onto layer
Alpha Transparency of the layer
Elevation Offset Elevation Offset applied to the layer
Bounds  
Size The extent of the layer
Offset The location of the layer

 

Terrain-specific attributes


The terrain attributes of a terrain layer in the inspector.

Attribute Function
Map The heightmap image.
Terrain resolution u The number of terrain mesh vertices in u direction.
Terrain resolution v The number of terrain mesh vertices in v direction.
Value filtering The filtering applied to terrain height and sampling. Choice of either none (pixelated), or smooth (linear) filtering.
Texture The texture image overlayed over the terrain mesh
Wireframe alpha The transparency value used for wireframe rendering.
Enable elevationDelta If enabled, the built-in function "elevationDelta" returns the elevation deltas resulting from the terrain alignment tool. If disabled, the function returns 0.
attr elevation The definition of the terrain elevation which is used to create the terrain mesh.

Further Reading

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