PhotoScan to Shapeways

Written by Paul Bourke
June 2015


The following are some brief notes around the conversion of PhotoScan reconstructed models to Shapeways for 3D printing. Some additional notes can be found here around editing in MeshLab and thickening in Blender. This document is mostly aimed at the file formats available from PhotoScan and the requirements for Shapeways. As is often the case the difficulty here arises from poor software support, in this case it arises from deficiencies on the Shapeways site, they are: incomplete support for textured meshes through OBJ and 3ds files, the incomplete support for zip archives (in this case those created on the Mac by MacOSX).

Build model in PhotoScan

It is assumed here that the model is a closed surface, that is, has no holes. Photoscan has a number of tools to facilitate this, see the hole closing and the extrapolation option in the mesh building stage.


Example used in this tutorial

Export

At the time of writing the following formats are recommended on the Shapeways site.

The following export formats are available from PhotoScan.

A commentary/comparison of the formats in common is

  • wrl, in the authors opinion, is not an encouraged format. wrl was never intended as an interchange format and is often fraught with problems as a consequence.

  • stl does not support textured colour but would generally be the choice for monochrome models, highly reliable due to its extreme simplicity (albeit inefficiency due to not sharing vertices). It was designed explicitly for rapid prototyping.

  • obj saved models consist of at least three files, sometimes more. These will be a .obj file which contains the mesh geometry, a .mtl file which is a description of the textures, and one or more texture files. Unfortunately, while Shapeways used to support textured .obj files which are semi standard for reconstruction work, they recently removed that capability, disappointing.

  • 3ds will consist of at least 2 files, the geometry file with a .3ds extension, and one or more texture files. Photoscan can export textures as JPG or png images as required by Shapeways, see the "Export model" dialog options.

  • dae will consist of at least 2 files, the geometry file with a .dae extension, and one or more texture files.

Zip

The preferred formats then are: obj, 3ds and dae. Unfortunately Shapeways has discontinued obj support. At the time of writing Shapeways rejects the 3ds file from PhotoScan, despite every other package tried working fine.

So, only dae left. The last part of the story is how to combine all the assets (geometry file and texture) into one package for Shapeways. Instead of offering multiple file uploads of the assets, pretty simple these days, they insist on a single zip file. Unfortunately it seems Shapeways is a little fussy over what can be in the zip file. Specifically, the zip file that MacOSX creates by selecting files and right clicking isn't accepted, despite every other unzip (and other 3D printing companies) accepting it.

If one is familiar with the command line then this creates a zip file that Shapeways can handle.

   zip slab3.zip slab3.jpg slab3.dae

There are no doubt zip utilities that create zip files acceptable to Shapeways, however iZip does not work, the uploaded zip files seem to crash the Shapeways upload system. Keka does seem to work. YemuZip does seem to work. Others can be tried by the reader ... note that the issue seems to be around other files some zip applications include in the archive, so disabling that in the applications preferences (if possible) is encouraged.


Notes

  • Now that Shapeways offers a scaling feature, going straight from PhotoScan to Shapeways should now be a viable route. Since PhotoScan models can be arbitrary dimensions, in the past it was necessary to scale prior to Shapeways upload.

  • It would be "nice" if Shapeways supported a format that encapsulates all the assets without the need to zip the collection, the obvious choice would be u3d.