Same synth input with different results?

  • Question
  • Updated 7 years ago
I created two synths with the same 220 images (on accident, because of the "stuck at publishing stage" issue mentioned in other threads here).

The odd bit: One is 93% synthy, the other 99%. One has two 3D groups (I think), and the other has three or four (how DO you tell - and how do you eliminate/merge them?)

The synths:

http://photosynth.net/view.aspx?cid=0...
http://photosynth.net/view.aspx?cid=d...

Any clues?

-Dane
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Dane Jasper

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  • confused

Posted 7 years ago

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Nathanael Lawrence

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I've wondered about this very thing. Was your computer busier with other programs when it was calculating the one that resulted in only 93% synthy?
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Dane Jasper

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Nope - and it's a computer - same input, you'd expect same output, right?
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Nathanael Lawrence

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It does seem logical. I'll be curious to hear what Live Labs has to say about it.
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David Gedye, Principal Group Manager

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Photosynth can give a slightly different result if you give the images to it in a different order. The reason for this is that the reconstruction phase of the algorithm is an optimization problem that can never be perfectly solved, and final results depend on certain choices of an initial pair of images to start with. If you give the images in a different order, then it starts "growing" a consistent 3D solution from a different seed, and the results will be slightly different.

Does that help?
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Dane Jasper

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Yes, I guess that makes sense - but in both cases, I just selected an entire directory full of images, so I'd have thought they'd be in the same order.

-Dane
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I had the same exact issue. Got stuck on the publishing phase, exited out, then re-synthed and ended up with 2 of the same synths with different percentage ratings. Same order of pics in both... Who knows i might play with it. If i am unhappy with my percentage maybe i'll try and swap the pics around and see what happens...
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Matt, Employee

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Synthing isn't completely deterministic, so you might get slightly different results each time. The differences should not be very big. You will have a very weak connection that becomes disconnected or vice-versa.

The issue of stuck in publishing is something else happening. Sometimes the process of publishing takes longer than other times. A lot of files have to move across a lot of servers. Occasionally one of these files will get lost causing the synth to never get published. You'll have to synth again to get it to the servers. Check on your "Your Synths" page to see if it's there before resynthing.