#Import and export

#How to open someone else's file

File -> Import… is one item for every format. The chooser shows every file the program reads; the file's extension decides what it becomes: a solid, a mesh or a sketch. If the program does not read the format, the status line names the file and lists what can be opened.

Insert component in an assembly opens the same chooser, but only with what can become a part: STEP, IGES and STL. A flat drawing cannot become a part - open it from the File menu instead.

#What can be read

• STEP — exact geometry with faces and edges. The best way to get someone else's part: you can work with it as with your own, except for the history — it is not in the file. An assembly in the file comes in as a tree of sub-assemblies and parts in their places, with names and face colours.
• IGES — exact geometry too, an older format: many archives of machine-shop and design programs are kept in it. The file usually holds surfaces rather than solids; the ones that close are sewn into solids, and an open surface comes in as a shell. Surfaces the author gathered into a group are sewn into one part under the group's name, in the file's colours; a group of groups comes in as a subassembly. An IGES with no surface at all is a drawing: its curves go into a sketch, as with DXF.
• STL — a triangle mesh only. There is no shape as such in it, so precise operations are impossible until it is recognised into a solid (below); it is good for overall size and for printing.
• OBJ — a mesh too, the format of rendering and sculpting. Every object in the file becomes a part of its own; OBJ carries no unit, so the program asks what it is drawn in.
• PLY — the mesh of 3D scanners, as text or binary. The geometry is taken; the colours and normals of the points are not needed and are passed over.
• glTF (.glb, .gltf) — the format of browsers and rendering: a scene of nodes, each in its own place. A node that holds others becomes a subassembly, and a node that carries a mesh a part in its place, under its name. glTF keeps metres and takes Y as up - this is turned into millimetres and Z on the way in. A node's scale goes into its mesh: a part's place is a turn and a shift only.
• 3MF — a mesh for printing, with the unit inside the file: a model drawn in inches arrives in millimetres at the right size. Every build item of a 3MF becomes a part in its place, under its name and in its colour; an object of named parts comes in as a group of those parts, to any depth.
• AMF — the predecessor of 3MF, a mesh for printing with the unit inside too; it is sometimes zipped, and that is read as well. A constellation becomes a subassembly, and its objects parts in their places.
• DXF and SVG — flat outlines, they land in a sketch.

#Units and scale

STL, OBJ and PLY carry no unit, and a file that names one can name it wrong. So once a file is read, a question comes up at the bottom of the window, Units and scale: what the file is drawn in (for a file without units) and by what factor to take it. The model in the view changes with the answer at once. Enter or Import keeps it so as one step of undo; Esc cancels the import altogether. A file with units is asked about only when the model comes out under 1 mm or over 10 m - or always, when the settings say "Ask for units and scale on every import".

To change the scale of a file already in the document, double-click its node in the tree - Import: file name or Mesh from a file: file name - choose Edit in the node's menu, or press Edit in its properties. The node lies in the part the file came into: if it does not show, step into the part with a double click first. The same window opens at the factor the file stands at now, and everything that came from the file changes together. Enter or Apply keeps the new scale as one step of undo; Esc leaves it as it was. If the status line says the bodies are still loading from the file, try again when loading is done.

#What can be written

Everything goes through File -> Export project: a submenu of every format, the exact ones on top, the meshes below the line. On a component in the tree the same submenu is called Export and writes only the visible bodies of that component.

• Export to STEP — exact geometry as the assembly tree, with names and colours. This is what goes to a customer and to a machine.
• Export to IGES — exact geometry written as faces. For programs that do not read STEP - most often older machine-shop ones.
• Export to STL — triangles, for printing. Here the document's geometry accuracy matters: it decides how finely the surface is divided. It travels with the file, so the same project gives the same STL to two different people.
• Export to OBJ — the same mesh at the same choice of quality, one object per body: for rendering programs.
• Export to PLY — the same mesh as a binary file with exact coordinates: for programs that work with scans.
• Export to glTF — the same mesh as one .glb file, one node per body, in metres with Y up, as browsers and rendering programs expect.
• Export to 3MF — the same mesh for printing, with the millimetres stated in the file itself: at the printer it will not arrive in inches.
• Export to AMF — the same mesh for printing programs that expect AMF, in millimetres.

#Things to remember

• A mesh is turned into a solid by the Part tool Recognise: exact surfaces (a hole becomes a cylinder) or a polyhedron as it is. The solid can be cut, drilled and sketched on. A large mesh takes long to recognise - tens of seconds for a hundred thousand triangles.

• A mesh lands where its file puts it - as the exact formats do. If a model comes in far from the origin, move it like any other body.

• Only visible, not consumed bodies are exported: intermediate states of a chain are not.

• An imported body lives in the timeline as its own feature: you can move, cut and drill it, but you cannot “go back to its sketch” — there never was one.

• A sketch goes out as a flat drawing: the right button on the sketch in the tree -> Export to SVG… or Export to DXF….

• To simplify an import there is the Remove face command: it takes away a hole or a pad that should not be in someone else's model.