Tuesday, December 12

Photogrammetry – Creating Virtual Duplicates of Real-World Objects

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Firstly, I’ll point out that photogrammetry is a very specialized technique.  As a result of this, most tools available for photogrammetry run into the tens or hundreds of thousands of dollars.  However, it is possible to piece together a few options that can produce usable results for much less cost.

Photogrammetry is an alternative to laser-based 3d scanning of an object.  Photogrammetry allows the user to take a collection of photos of an object, taken from different angles, and extract depth information from these digital images, effectively generating a 3d model through cross-reference of corresponding points on the multiple views of the same object.

Here, I will list a few options:

-ImageModeler.  ImageModeler is Autodesk’s entry in the photogrammetry market. It’s in the thousand-dollar range.

-PhotoModeler and PhotoModeler Scanner, the former being around $900, the latter $2500.  Also expensive.

-PhotoSculpt.  At $99, this is in an ordinary person’s price range, and it’s easy to use.  The downside is it only extracts 3d geometry from two photos (until a new version comes out)… still, it is possible to process a collection of image pairs to create a batch of 3d models, and then stitch those models together in a 3d application to form a complete model of an object.

-Canoma.  Adobe bought this innovative and user-friendly 1999 photogrammetry app and then did nothing with it.  That, in my opinion, was a huge blunder; they had an opportunity to produce a great mass-market photogrammetry tool and they didn’t.  The tool is now outdated and unsupported but you can find used boxed copies for around $150-$200 in some places (Ebay, for instance)

-Insight3d.  Open Source.  I’d love to see this app developed further.  As is, it has some flaws (limited modeling tools, for one) but it is definitely possible to extract a point cloud or a complete mesh from a set of photos with this app.  As with any such program, be sure your photos are high-resolution, taken from many angles, and have a minimum of noise for best results.

PhotoModeler Lite 3.1 – For a while, PhotoModeler had a freeware, limited version.  They discontinued it and it doesn’t run on newer OSs, but it still is floating around on the web in a few places.

Another option is to model the geometry by hand in your favorite 3d app, not accurately necessarily, but as close a guess as you can manage, and map it with textures extracted from the real-world scene. This can produce passable results. 

I took a series of photos of a segment of my living room to test this.  I took pictures of every surface, and cleaned up the images in Photoshop, making heavy use of the “Perspective Crop” and ‘clone” tools, among a few others.  I then modeled an imitation of the real-world scene in Lightwave (any good 3d app could do, though – Blender would work just as well)  and mapped these textures onto it.

The result is a CG scene which, while not a stereographic 3d scan or “Real” photogrammetry, comes reasonably close to replicating the original scene:

http://www.triumphantartists.com/cg.jpg

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