Project Description

SynthExport allows you to export images, point clouds and camera parameter data from synths on Photosynth. Point clouds are downloaded automatically and converted to formats that are compatible with most 3D graphics applications. Camera information such as position, focal length and lens distortion of each image is stored as a CSV file.

Screenshot of SynthExport

Features

The data you can export depends on the synth type.

Images Point clouds Camera parameters
v1 Photosynths Yes Yes Yes
ICE/mobile panoramas Cube map No No
v2 Photosynths (spin) Yes1 Yes No
v2 Photosynths (panorama) Yes1 No No
v2 Photosynths (walk) Yes1 Yes No
v2 Photosynths (wall) Yes1 Yes No

1 Exported images are lens-corrected versions of the original source images.

System requirements

SynthExport requires Windows Vista or higher with .NET Framework 4.5.1 installed. SynthExport 1.1.0 is the last version with Windows XP support and requires .NET Framework 3.5 SP1.

Instructions

  1. Start SynthExport
  2. Go to your synth on the website and copy the address from your browser, e.g. http://photosynth.net/view.aspx?cid=58b232f9-3e1b-44e4-943d-b133e0583c6a. URLs of synths on Bing Maps are also accepted.
  3. Paste the address in the URL text box of SynthExport and click "Load"
  4. Select the data you want to export (images, point clouds, camera parameters)
  5. Choose one of the file formats and click "Export".
  6. Choose the destination folder for the exported data.

FAQ

  • What is a point cloud?
    • Each synth contains a cloud of colored points in 3D space that have been extracted by the synther. If enough photos have been taken these points form a fairly accurate 3-dimensional model of the photographed object.
  • Which output formats for images are suppported?
    • Images of v1 and v2 photosynths can be exported as JPEG or PNG files. The exported images of v2 synths have been lens-corrected and may not look exactly like the originals (extreme case). Panoramas from Microsoft ICE and the mobile apps are exported as cube maps which can be stitched together again by ICE or other pano tools (note: ICE is not ideal for cube maps). Still, there is a separate option for generating an ICE project file if you want to use ICE.
  • Which output formats for point clouds are supported?
  • What are camera parameters?
    • Photosynth is able to estimate the position and direction of the camera from each image, as well as the focal length and radial lens distortion. For v1 photosynths, SynthExport can export this data as a CSV file with the following columns:
      • Image ID
      • Camera position X
      • Camera position Y
      • Camera position Z
      • Camera rotation about X axis
      • Camera rotation about Y axis
      • Camera rotation about Z axis
      • Image aspect ratio
      • Focal length (relative to the size of the CCD)
      • Radial lens distortion K1
      • Radial lens distortion K2
  • What are coordinate systems?
    • Photosynths often have more than one coordinate system. This happens when the synth contains groups of images that don't have any image features in common or when the synther simply wasn't smart enough to put everything together properly. Each coordinate system is associated with at least one image, and has in most cases a point cloud. Camera positions and point clouds are not compatible between different coordinate systems. Therefore, each coordinate system with its point cloud and its camera parameters are exported to separate files.
  • Which programs are suitable for working with point clouds?
    • You may want to use software that is capable of meshing colored vertices and reconstructing surfaces. Personally, I don't have tested any other software than MeshLab which seems to do the job quite good. Theoretically, however, all programs that are able to import one of the output formats should work.
  • Microsoft ICE introduces black seams when stitching an exported panorama cube map
    • This is an annoying flaw in Microsoft ICE. The best option is to use another stitching tool such as Hugin or PTGui that handle cube maps better. There are two workarounds for ICE though:
      • Set the focalLength values in the .spj ICE project file to something between 0.99-0.9995. The images will then be slightly distorted but the seams disappear.
      • Export your image in ICE as Photoshop PSD file with layers. Open the file in GIMP, and for each layer click Layer -> Transparency -> Alpha threshold and set the threshold to zero. Then save the image again and the seams should be gone.
    • Note that you can still use ICE to publish to Photosynth, the artifacts do not show up there.

Links

Last edited Mar 4 at 12:23 PM by christoph_hausner, version 9