Hack Shack – Handout

3D: Photogrammetry with 123d Catch

Definition: Photogrammetry can be used to create 3d models of buildings or objects.   How?  Overlapping images (at least 60% or more) are combined using photogrammetric software (PhotoScan or 123d catch) to create point clouds which are then translated into a 3d mesh.  The mesh is covered with a texture comprised of photographic images giving it color and detail.

Real world applications?

You can use your generated mesh in several ways:

  • 3d file for viewing online
  • 3d prints
  • Animations or games

Resources: 

123d catch: http://www.123dapp.com/catch

Mesh mixer : http://www.meshmixer.com

Photographing objects for 123d Catch

  1. Select an object (make sure it’s not transparent, reflective or shiny–no glass or mirror).  Avoid subjects or objects with occlusions or that self-occlude, such as a chair.
  2. Place the object in an evenly lit environment on an empty table or pedestal if possible. Incandescent bulbs or natural light are your best bets.  No flash can be used. Remember the object needs to remain stationary.  The photographer moves, NOT the object.  If you’re photographing a person they will need to remain completely stationary.
  3. You can make images with a DSLR or your iphone/ipad!  You’ll need a minimum of 24 images and a max of 40 for the mobile devices. The more images,  the better quality mesh.  If you’re shooting with your DSLR a minimum of 50 are needed and a maximum of70 images can be used. The more the better!
  4. Visualize a circle around your object.  It’s probably easiest to envision something like this, below.  At minimum you’ll need to take 5 images, evenly spaced, between each quadrant (N, E, S, W).
  5.  
  6. Next, be sure to frame your images as tightly as possible, keeping the subject in the frame and getting as little background as possible.  Be aware of your background.  It shouldn’t be reflective either. Go around your entire image keeping the same distance from the subject.  This will at minimum take up 24 images.  Then, depending on what you’re shooting with use your remaining shots to get angled shots (above and below the image).  Leave your last shot for the top of the object.
  7. Once the images are shot you can upload them to the cloud via 123d catch or through the 123d catch application on your PC.  This is simple once you have a 123d catch user ID and password set up.
  8. Once your files are uploaded you’ll be able to rotate and review your 3d model.
  9. Models can be finessed and edited in the cloud, using 123d mesh software on a PC, or though a 3rd party editor like Meshmixer.  We’ve gotten the best results from Meshmixer, as 123d catch often crash (computational heavy work is some time unreliable on the cloud).
  10. If you use with Meshmixer (freeware) then you’ll need to download your zipped Mesh Package File from 123d catch.  Once you open that you’ll need to open the .obj file for editing and repairing in Meshmixer.  Save your file as a stl for 3d printing.
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One thought on “Hack Shack – Handout

  1. Hey folks – What formats can be uploaded to 123DCatch and what is the maximum resolution or file size that can be used in 123DCatch to assemble a photo? Does 123dCatch compress all files to some standard resolution to then create their mesh and the final 3dp file format?

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