CAD Assistant

CAD Assistant

A viewer and converter for 3D CAD files:


Version 1.3.0 (2019-08-15)

OPEN CASCADE CAD Assistant is a viewer and converter for 3D CAD and mesh files, free for both personal and commercial use.

CAD Assistant is based on open source libraries (Open CASCADE Technology, Qt, FreeType, FreeImage, etc.) and employs open formats for CAD and mesh data (STEP, IGES, BREP, DXF, SAT (ACIS), glTF, JT, PLY, STL, OBJ, 3DM).

It is made to promote open technologies and brings the power of these technologies to the hands of engineers working with 3D data.

Originally developed as a testbed and showcase for the Open CASCADE Technology on mobile platforms, CAD Assistant has been appreciated as fast and handy 3D viewer by thousands of end-users worldwide.

Since version 0.7, CAD Assistant is available also on desktop platforms.

OPEN CASCADE provides support and consulting services for its open source products and free applications, including CAD Assistant.

Please contact us if you have a request regarding CAD Assistant or are interested in other our services.

Use the following links to download and install it for your platform:

v.1.2.1, 2019-01-14

v.1.2, 2018-10-30

v.1.1, 2018-08-10

v.1.0, 2018-02-15

v.0.9, 2017-04-03

v.0.8, 2016-11-26

v.0.7, 2016-07-18

v.0.6, 2015-09-10

v.0.5, 2015-05-15

Basic CAD model viewing and converting

Basic functionality is provided by XDE component of OCCT. The supported file formats are:

  • BREP: shape geometry and assembly structure (defined by nested compounds).
  • IGES (5.1 and 5.3): shape geometry, colors, top-level object names, file information.
  • STEP (AP203 and AP214): shape geometry, assembly structure, colors, names, validation properties, file information.

CAX-IF test model in CAD Assistant for Android

Assembly structure of the model can be navigated through the tree browser, displaying the names of parts and their instances in the assembly (if available). Assembly components can be hidden or shown as necessary to inspect the model.

Navigation and selection in the assembly structure

The selected sub-assembly or part can be queried for its properties including names, product information as well as geometrical ones (area, volume, and centroid).

Properties of a selected part

The model can be saved into a neutral (STEP, IGES) or OCCT internal (BRep) format.

Viewing mesh data

Viewing mesh models with associated data, implemented using the MeshVS component of OCCT, is an additional functionality included in CAD Assistant.

Mesh can be read from files in PLY format. This format is chosen for its simplicity and capability to store data associated with mesh nodes and elements. If you have a model represented by mesh in your application, it can be saved easily to PLY format and viewed on a tablet. Additional data (RGB color or scalar) can be added to each polygon or node.

CAD Assistant allows you to view any mesh in wireframe, shaded, and shrink modes. If a mesh contains associated color or scalar data, it can be viewed with elements colored according to the selected quantity. For scalar quantities a color scale is shown, providing controls to narrow the range of displayed colors if necessary to inspect the data with more details.

Results of strength analysis of bulk carrier ship (courtesy RINA S.p.A.)

Common operations

CAD Assistant is optimized for devices with multi-touch screen and provides intuitive manipulation of the view by finger gestures:

  • Rotate by single finger
  • Pan or zoom by two fingers

The left toolbar provides buttons for fitting a model to the window and a choice of standard views. Settings submenu provides access to the viewer and application options, file information, and the message log.

CAD Assistant integrates with the OS so that applications supporting file associations will launch it for opening files of relevant types. For instance, you can open a STEP file sent to you by mail by tapping on the attachment in your mail client.

Save file dialog allows saving the current image of the model to PNG format. If Mail is selected as the target directory, the mail client will be automatically started with the saved file as an attachment.

Supported platforms

Currently CAD Assistant is provided for:

  • Windows platform 10 / 8.1 / 7 SP1, 64-bit (with HiDPI display support)
  • OS X platform 10.10 Mavericks and above
  • Android platform, supporting Android versions 4.1 and above.
  • iOS platform (iPad, iPhone), supporting iOS versions 5.1.1 and above.

It has been tested to work on a range of modern middle-level tablets and smartphones. However, we warn smartphone users that the application supports only landscape screen orientation and this might be inconvenient on phones.

Known issues

Depending on a device, opening large files may take time. Devices with low-range graphic processors could be slow when a large model is displayed in the viewer. For scenes consisting of several millions of triangles, the system may kill the application with no warning due to GPU problems. In general, files less than 50 MB can be considered safe for opening on most devices.

If you obtain a low memory error when loading large files, we recommend restarting the application.

Development and support

OPEN CASCADE will continue development of CAD Assistant, improving its performance and adding new features.

Please contact us if you have ideas how to improve the application or wish to use this technology for development of customized solutions for your business.

Use the Forums to post your comments; your feedback is always welcome! We will appreciate users sharing their experience of using the application on particular devices.


The application is provided AS IS, without warranty of any kind.