File formats that can be imported into Meshmixer.
The canonical 3D printing format. Unfortunately this is also just about the worst way to store a mesh! See below under the Preferences section for details. We support both ASCII and Binary STL. For Binary STL, we support face colors, but only one of the modes (there are two conventions and there is no way to tell which is which!). And we bake these face colors into vertex colors, so there is some blurring.
The Wavefront OBJ format is widely used in many industries, and this is the format we have the most extensive support for. OBJ can store arbitrary polygons, but we always convert to triangles on input. We support the color-per-vertex extension used by some other software (eg ZBrush). OBJ is also (currently) the only format where we support importing texture maps (only diffuse maps). We really prefer the texture images to be PNG or JPG formats. For more info on how we handle groups in OBJ files, see the details below in the Preferences section.
Additive Manufacturing Format (AMF) is a relatively new format that was designed to replace STL for 3D printing. Frankly we still think this format is not as good as OBJ, but that's just our opinion. We only support a subset of the expansive AMF format, in fact we only support the triangle-mesh portion.
Polygon File Format PLY is a format produced by many 3D scanners. We support ASCII and Binary PLY, and we can read per-vertex colors in PLY files. Note that PLY is quite a tricky format, so if you have a PLY file that gives you an error, please send it to us and we can probably help.
Meshmixer support for the 3MF format is relatively new, so there may still be bugs or other issues. This format supports vertex colors and texture/material information.
In addition to being able to Open a .mix file (which replaces the current scene), you can Import a .mix, to append the objects to the current scene.
Note that for all these formats, we discard the normals stored in the files. We always re-estimate our own normals from the mesh triangles. Also, most of these formats don't tell us what units they were saved in!! So for formats that don't (everything except DAE and AMF), we assume millimeters.