File formats

open / import read a file into the scene; save / export write it. The format is chosen by extension.

Format	Import	Export	Notes
.serp	✓	✓	Native: JSON scene + embedded binary BREP, thumbnail and metadata
.step / .stp	✓	✓	Exact BREP exchange via OpenCASCADE
.3dm	✓	✓	Rhino: exact NURBS curves both ways; breps import as trimmed NURBS faces, export as meshes (use STEP for exact surfaces); layers with visibility/lock, hidden objects and Attribute User Text preserved; writes Rhino 5–8
.obj	✓	✓	Tessellated mesh with .mtl colours
.fbx	✓	✓	Autodesk FBX (binary) — tessellated meshes; imports/exports cleanly to Blender, Maya, Unreal, Unity
.stl	✓	✓	3D printing — watertight binary (or ASCII) STL for slicers, with draft→ultra mesh-quality presets on export
.3mf		✓	3D printing — modern container with real units, colour and multi-part; preferred by Bambu Studio / PrusaSlicer / Cura
.dxf	✓	✓	Curves/meshes with layers; layout sheets export at paper scale
.svg	✓	✓	Paths import as curves (béziers exact); layouts export as vector SVG
.glb		✓	Binary glTF with materials (Unreal / Blender / web)
.usda / .usd		✓	USD for virtual-production pipelines
.e57	✓		Point clouds: separate registered scans with RGB colours; Cartesian and spherical coordinates
.skp	✓		SketchUp 2013 onward: groups and components as solids and polysurfaces, tags as layers, material colours

Notes

• E57 scans. Choose File > Import or drag an .e57 file into the window. Each scan becomes a separate named point cloud, positioned using its stored scan pose. E57 coordinates are in metres and are converted to the current model units. Invalid samples are omitted; 16-bit colours are converted to 8-bit RGB for display. Save as .serp to retain the imported clouds. Embedded photographs, intensity and scanner-specific metadata are not imported.
• SketchUp files. Choose File > Import or drag a .skp into the window; SketchUp itself is not needed, on any platform. Each group or component at the top of the model becomes an object for every separate body in it, joined into a solid where its faces close, so push/pull, booleans and fillets work on it; stray edges come in as curves beside it, and what one group made is grouped so it selects together. Faces loose at the top of the model come in one object per tag. Tags become layers with their colours and visibility, and a group's material colour becomes its colour. Sizes are converted from SketchUp's inches to the model units. Curved surfaces arrive as the flat facets SketchUp draws them with, every facet edge showing; textures, face-by-face colours, scenes and dimensions are not imported. The file is read by OpenSKP, which does not yet read every file: some saved by SketchUp 2018 and 2019 and by very old versions fail, and say so. Export those from SketchUp as OBJ, FBX or DXF instead.
• Rhino user text. An object's Attribute User Text arrives with it and is written back out on export, in the file's order, and a .serp keeps it too. Properties shows and edits it under User text. A placed block comes in as its pieces, so each piece keeps its own keys and takes any it lacks from the block that placed it; geometry user text and the document's own user text are not read.
• Exact vs. mesh. .serp and .step carry exact geometry both ways; .3dm is exact for curves but writes surfaces and solids as meshes — for an exact round trip through Rhino, export STEP and import it there. .obj, .fbx, .stl, .3mf, .glb and .usd are tessellated meshes — the display deflection (or STL quality preset) sets how fine.
• Layouts. exportpdf and exportsvg write drawing sheets, honouring linetypes and hidden-line detail modes.
• Coordinate system. Serpentine3D is Z-up. FBX export declares the Z-up axis system so orientation survives into Blender and others.
• Headless. Every format works from a script — doc.export("part.step") or serp3d-batch (see Script & automate).