JT Reader

The JT Reader provides full access to the Assembly, Visualization, B-rep and View & PMI Data stored within a particular JT file. A file does not need to have a particular extension to be read correctly by HOOPS Exchange however the file extension of JT files that you can expect to be loaded by HOOPS Exchange is:

  • .JT

Our readers are updated to the latest released version within 90 days of the release of the authoring software. You can see the exact version supported in the current release here.


The assembly can be defined in a series of files or in a single monolithic file. Full support for the layer and filter information is included. Incremental load is supported by our JT reader (except for metadata), even with monolithic JT files.


A JT file can contain three different types of B-rep data: Parasolid B-rep, JT B-rep, or ULP (Ultra-Lightweight Precise) B-rep. We currently support all three types. However, our JT reader does not support ULP B-rep for JT 10 files.

The JT B-rep is relatively simple and only supports geometry in NURBS form. The only types of surface and curve geometry that can be found in a JT B-rep is:

  • B-spline surface

  • MCS (3D) curves

  • PCS (2D) curves

The Parasolid B-rep is not restricted and can be anything from the official Parasolid B-rep. The geometry available is also listed in the Parasolid section but for completeness it is included here. The list of surface types available in Parasolid B-rep is:

  • Blend surface

  • B-spline surface

  • Cone

  • Cylinder

  • Offset surface

  • Plane

  • Sphere

  • Revolution surface

  • Swept surface

  • Torus

The list of curve types available in Parasolid B-rep is:

  • B-spline

  • Circle

  • Ellipse

  • Intersection curve

  • Line

  • UV Curve


We fully support the loading of tessellated objects from a JT file. HOOPS Exchange can load the different LODs and the developer instructs HOOPS Exchange which LOD to load via the “level of detail” reading option. Support is provided for tessellated wireframes and point clouds.

HOOPS Exchange also handles Primitive Set Shape. These are boxes, cylinders, pyramids, spheres, and prisms stored in the file with the minimum data necessary to procedurally generate them.


Full support for views including the visibilities of objects associated to views is supported.


The JT reader provides access to the PMI information to the full extent of the JT specification. HOOPS Exchange is able to retrieve the link between PMI data and the geometry.

The different PMI types available in JT are:

  • Datum

  • Datum target

  • Dimension

  • Line weld

  • Spot weld

  • Surface finish

  • Measurement point

  • Locator

  • Reference geometry

  • Design group

  • Feature control frame

  • Coordinate system

  • Note

The JT ISO standard supports tessellated PMI, with semantic PMI information attached as attributes. The JT reader doesn’t interpret this data, but exposes them as it is:

  • Markups with tessellation from the JT file, with ModellerAttributes for the raw semantic information


All the properties and meta-data contained in a file are exposed to the user.

Import Options Specific to JT



Our JT reader has the following limitations: * No support of Ultra Lightweight Precise (ULP) B-rep in JT 10. This is a lossy, compressed B-rep that Siemens introduced recently. * No support of LightWeight Precise Analytic (LWPA) data. * No support of wireframes stored as splines (but we support tessellated/polyline wireframes). * No support for advanced graphics including textures, lights and shaders. * No support for section planes.