3D Model Converter

About the 3D Model Converter

Open a 3D model — STL (binary or text), OBJ, PLY, glTF / GLB or 3MF — and convert it to any of them. Look at it from every side in the preview, check its size, surface area, volume and whether it is closed (watertight) for 3D printing, and fix the usual problems on the way: a model drawn in inches that comes out 25.4 times too small, one exported Y-up that lies on its back in the slicer, or parts that should be one object.

Several files can be combined into one model. Everything happens in your browser; the model is never uploaded.

Formats

• STL: binary and ASCII, including ASCII files with several solids. Written as binary (smallest) or ASCII.
• OBJ: vertices, faces of any number of sides (split into triangles), objects (o) and vertex colours (v x y z r g b). Materials (.mtl), texture coordinates and normals are not read.
• PLY: ASCII and binary (little- and big-endian), with vertex colours. Written as binary or ASCII.
• glTF 2.0: .glb, and .gltf with embedded or separate buffers; every triangle primitive of the scene with its node transforms. glTF is defined in metres with Y up, so it is converted on the way in and out. Draco and meshopt compression are not supported.
• 3MF (core specification): objects, components and build items with their transforms, and the model’s unit (micron to metre). Several objects stay separate objects.

Conversions keep the geometry — triangles, and vertex colours where both formats have them. Materials, textures, normals (they are recalculated by every program), animations and scene cameras are not carried over.

Units and orientation

STL, OBJ and PLY store bare numbers. Slicers read them as millimetres, so a model drawn in inches arrives 25.4 times too small and one drawn in metres 1000 times too large; tell the converter what the numbers mean and in which unit to write. 3MF stores its unit (the converter writes it) and glTF is always in metres.

3D printing uses Z as up. Many 3D apps and game engines use Y as up, so their exports lie on their back in a slicer — Stand it up turns the model a quarter turn about X; Lay it Y-up does the opposite. Mirror flips the model and keeps its triangles facing outwards. On the build plate centres the model and puts its lowest point at Z = 0.

Measurements

The size is the bounding box along X, Y and Z, in the unit you write. The surface area adds up every triangle. The volume — useful to estimate material — is computed from the signed volumes of the triangles and only makes sense for a closed model: one where every edge is shared by exactly two triangles. The converter counts edges that belong to one triangle only (holes) and edges shared by three or more; such meshes may need repairing before printing.

Limitations

• Geometry only: materials, textures, texture coordinates, animations and skins are not converted. Vertex colours are kept between OBJ, PLY and glTF.
• Not supported: Draco- or meshopt-compressed glTF, 3MF extensions (beam lattices, slices, materials, parts in other model files), and other formats such as STEP, IGES, FBX, DAE, 3DS or Blender files.
• It does not repair meshes: holes and overlapping triangles are reported, not fixed.
• Models are converted in your browser’s memory: files of up to about 700 MB in total. The preview needs WebGL 2.

Privacy

Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.