Terragen terrain MIME Type

Understand Terragen terrain files, compatible tools, and Poly preview, search, and agent support.

MIME type details for `model/x-ter`

In active use

MIME type	`model/x-ter`
Extensions	`.ter`
Magic number	`TERRAGEN followed by TERRAIN and a space`
First standardized	Unknown; Terragen terrain specification
Created by	Planetside Software
Browser support	Requires a compatible 3D web viewer
Example applications	Terragen
Poly support	Yes. Poly recognizes supported Terragen terrain files and provides 3D features when readable geometry is present.
Indexed by Poly	Yes. Search by filename and, after successful processing, visual similarity. Available geometry counts appear in 3D Details.
Preview in Poly	Partial. Interactive inspection of supported geometry; authored appearance and animation may differ.
Poly agent	Partial. An optimized rendition of the 3D object or scene is provided to the agent, allowing compact yet information-rich multimodal interaction with 3D files. This requires an available visual rendition.

What does `model/x-ter` identify?

Poly uses model/x-ter to identify Terragen terrain files with the .ter extension. This is a Poly-recognized media-type label, not a claim of IANA registration. The format of the bytes still determines whether a file can be opened.

A .ter file stores a Terragen heightfield: a grid of elevation samples describing a terrain surface. It is not a complete Terragen scene. The file begins with the 16-byte identifier TERRAGENTERRAIN and includes terrain size and elevation data.¹

File structure and background

The format comes from Terragen's terrain workflow. Its scale information matters: stored terrain units should not simply be assumed to be metres. The specification describes the scale and altitude records used to interpret the surface.¹

A signature helps identify a candidate file, but does not validate its contents. Header values and the rest of the data must agree. Changing a filename or media-type label does not convert an unrelated file into this format.

Opening and working with the file

Open terrain data in Terragen using a Heightfield Load node. Planetside documents TER among the supported heightfield formats and explains the file-loading controls.² Keep the surrounding Terragen project if you also need the original atmosphere, lighting, or procedural surface setup.

Treat a terrain preview as a view of its shape. Elevation data does not include every ingredient of the landscape image you may remember from the authoring project. When comparing exports, inspect both the footprint and vertical scale.

Support in Poly

Poly lets you orbit, pan, and zoom around supported geometry. Find the file by name, or use visual similarity once its visual content is available. The details panel shows available mesh, material, vertex, triangle, and other scene counts.

Poly makes supported terrain geometry available for interactive inspection. A TER file alone does not reproduce a complete Terragen atmosphere or project. Geometry counts describe the visible terrain representation; they are not a geographic accuracy report.

An optimized rendition of the 3D object or scene is provided to the agent, allowing compact yet information-rich multimodal interaction with 3D files. You can ask about the object's visible shape or compare assets, while retaining the original for authoring work.

Conversion choices

For further terrain editing, keep TER or another heightfield format supported by your terrain tool. Export a mesh such as OBJ when another application needs surface geometry. Check the destination's scale settings before comparing or measuring the result.

Planetside Software. Terragen terrain-file specification. ↩ ↩²
Planetside Software. Heightfield Load. ↩