DTM Source Data
TerraForm lets you import DTM data directly into UE4, but for now you need make sure your DTM data meets the following standards. We’ll add support for more formats and other DTM specifications soon.
TerraForm needs 32-bit floating point DTM data in GeoTIFF (.tif) format. This is one of the most common formats of DTM data and any GIS software worth its salt can export it.
For now, TerraForm doesn’t re-project your DTM data. It simply reads the projection information and stores it in the TerraForm Landscape Anchor, so that other datasets can be imported on top (such as vector lines).
UE4 works in a linear Cartesian coordinate space, so your DTM data needs to be in a Local Cartesian Projection. You can use any projection that meets this criterion. We find the UTM Projection system with a WGS84 Datum works well in most cases and is a good fall-back option if you’re not sure what else to use. Make sure you pick the right UTM zone for your DTM though (e.g. UTM Zone 30N for UK).
Your DTM source file can be as big as you like within GeoTIFF file size limits (2GB). TerraForm can rescale the DTM to your desired landscape size, but the bigger the DTM, the longer the import process takes.
UE4 will only let you use a maximum of 8,129 x 8,129 vertices (Overall Resolution) in your landscape – any bigger than this and UE4 will crash, so it makes sense to try to make your DTM dimensions as close as possible to the overall resolution you want to use. For example, if you want to create a landscape with an overall resolution of 8,129 x 8,129 vertices, your DTM should be approximately 8,129 x 8,129 pixels.
TerraForm can create rectangular (non-square) landscapes, up to a maximum of 8,129 vertices in either X or Y dimension.
As long as the landscape you create is no more than 8,129 x 8,129 pixels, the pixel size can be whatever you like, within reason. We’ve successfully imported DTM data with a pixel size of 30m/pixel to create a landscape 200km x 200km. We wouldn’t recommend using single landscapes this big though – you can end up with object placement issues due to single floating point precision in UE4.
In UE4, distances are measured in metric (centimetres/metres) or imperial units (feet/inches) in 3-dimensions, along x, y, and z axes – you can set your units in the UE4 Editor: Edit > Project Settings… > Editor > Appearance > Units.
TerraForm supports data in both Metric and Imperial units, so you can set the UE4 Editor to your preference, however we’d recommend using metric units to keep things simple.
TerraForm supports common GeoTIFF compression algorithms, such as LZW and ZIP.
TerraForm first looks for DTM metadata (projection, datum, units, pixel dimensions etc.) in the header information embedded in the GeoTIFF file itself. If the header isn’t there, TerraForm will look in associated header files (.prj, .wld, .tfw etc.). Strictly speaking though, if the metadata isn’t stored in the file header, it’s not really a GeoTIFF. As long as your GeoTIFF DTM file has header information, TerraForm doesn’t require auxiliary files.