Open your first file

The app opens STEP (.step, .stp), IGES, BREP, GLB, glTF, FBX, OBJ, 3MF and STL files. A STEP, IGES or BREP file is converted first. The other formats open directly.

Open a file

1. Drag the file from your file manager onto the app window. You can drop it on the start screen or on the 3D view. While you hold it over the view, the words Drop to open appear.
2. Or press CtrlO and pick the file. On the start screen the same button is called Open file….
3. For a STEP file, a window called Import settings appears. The first time, leave everything as it is and press Import.
4. A progress card shows what is happening, with a running clock and a log of messages. A large assembly can take several minutes.
5. When it is done, the model appears in the 3D view. The parts tree on the left fills with its parts, and Properties on the right shows its totals.

What conversion does

A STEP file holds exact surfaces. The converter, running in Python on your computer, turns it into a GLB file made of triangles. Along the way it:

• reads the names and colours of the parts and the tree they are arranged in;
• tessellates the surfaces, which means it covers them with triangles (a big file is meshed by several worker processes at once);
• finds parts that have the same shape and stores that shape once (instancing);
• leaves out parts below a size you choose, if you ask for it;
• writes a plain GLB. It does not compress it: Draco and Meshopt compression are choices in the Export window.

The import settings for a STEP file

Surface quality

How closely the triangles follow curved surfaces: Clean, Coarse, Standard, Fine or Ultra. Clean makes few triangles and lays them in even strips along fillets. Coarse is the fastest and shows facets on curves. Ultra is slow and very smooth. Standard is the recommended one. Custom means your own numbers, under Tessellation.

Tessellation

The numbers behind that choice. Click the row to open it. It is explained below.

Colours and structure

Colours & hierarchy reads colours, names and the assembly tree. Geometry only is the fastest and gives you neither colours nor a tree. It suits huge files where you only need the shape.

What to read

Five switches for extra information in the file: Instance overrides, Keep layers, Materials, Product names and Validation properties. Each one adds a pass over the file. Instance overrides is the slowest on assemblies with many repeated parts. Keep layers keeps the CAD layer each part is on: it shows in the Properties card and Select by layer in the command search selects every part on one.

A part per colour

Off by default: a part painted in several colours stays one part, with a material for each colour. On: each colour becomes a part of its own, open along the colour seams.

Drop small parts

Leaves out parts smaller than this share of the model during conversion. 0 keeps everything.

Share identical shapes

Stores a repeated shape once. Leave it on.

Surface parts

Keeps parts that are open surfaces with no solid inside, such as sheet covers and shields. On by default. Off keeps only the solids.

Swap Y and Z

Stands a model up that comes in lying on its side.

Convert again

Ignores a stored conversion of the same file, if there is one, and converts from scratch.

Add to the open scene

Adds the file to the scene that is open, instead of opening it as a scene of its own.

Fit the view

Moves the camera so the whole model is in view when it has loaded.

Don't ask again for this format

Skips this window next time and uses the same answers. Leave it unticked until you know which settings you want.

IGES and BREP files, two other CAD formats, get the same window. FBX, OBJ, 3MF and STL files get a shorter version of it, with only Keep texture coordinates (UVs), Add to the open scene and Fit the view. GLB and glTF files open without it.

Tessellation: how the surfaces become triangles

Tessellation is the step that covers the exact CAD surfaces with triangles. You do not have to open this block: the choices of Surface quality fill it in for you. Open it when curves come in too faceted, or the model comes in too heavy.

Sag

How far a triangle may stand off the true surface, in millimetres. Smaller is smoother, and makes more triangles.

Angle

The most a curve may turn from one triangle to the next, in degrees. Smaller means rounder holes and rounder fillets (a fillet is a rounded edge).

Min edge

The smallest triangle edge allowed, in millimetres. It keeps tiny fillets and threads from filling up with thin slivers. 0 is no limit.

The five choices and Custom

Each choice sets the sag and the angle: Clean is 2 mm and 38°, Coarse is 1 mm and 30°, Standard 0.5 mm and 30°, Fine 0.2 mm and 20°, Ultra 0.05 mm and 12°. Type a number of your own and Custom is selected.

By part size

Fine on the large parts, coarse on the small ones. Small, medium and large parts each get a sag and an angle of their own, so the housing comes in fine and the screws coarse. Two fields, Small under and large from, say where the limits are, as a share of the model’s size: 5% and 30% to begin with. While it is on, the choices are greyed out. Min edge still applies.

Even strips

Meshes curved faces along their own directions, so a fillet is a row of even strips instead of a scatter of triangles. On by default.

Smooth shading

Takes the normals, the directions the light is worked out from, from the real CAD surfaces. A fillet then runs into the faces beside it without a visible seam, and sharp edges stay sharp. On by default.

Follow the progress, or stop it

• The progress card shows the latest message from the converter. Copy log copies all messages, which is useful when you report a problem.
• Cancel stops the conversion.
• If the conversion fails, the card says so. Press Copy log to keep the messages. See Troubleshooting.

Where the converted file goes

The converter writes the GLB into the folder inbox, inside app. The copy of your STEP file that was made for the conversion is removed when it finishes. To keep a GLB somewhere you choose, with a name you choose, use Save a scene or Export.

More than one file

• Opening a second file does not replace the first. It opens in a new tab. See Scene tabs.
• To put two files into one scene, use Menu, then Import into scene…, or press CtrlShiftO.
• To throw away every edit and load the file again as it was, use Menu, then Revert to source….