Forum : Bugs

Did the leaves fall off? Something not working right? Let us know how we can improve the Photosynth experience.


Topic: Synthing is all over the place

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AZJoe (Over 1 year ago)
Interesting program, but it seems to have a difficult time putting things together in the proper order.  Take a look at my synth:  http://photosynth.net/edit.aspx?cid=73abe820-4d04-4095-8aed-93d901d905a4  It jumps from here to there and back again.  Some of this I didn't expect to work very well, namely the rows of hangars and tie-dows, but the area in front of the terminal I expected to be synthed nicely. No joy.  It say's 97% synthed, but it is anything but.

It would be nice if there was someway to assign relative positions to images and let it go from there. The full auto does not work very well.

Joe
Nathanael (Over 1 year ago)
Joe, you're coming into this with wrong expectations. 

By default Photosynth attempts to figure out the positions of all of your photos relative to each other. If it can't discover how some fit into the rest, it puts them at the end of the list, regardless of the name of the file, when they were taken, or what order they were placed into the synther.

Of the photos that *do* link together (in your case 328 of 337) Photosynth cares about moving through them spatially, rather than chronologically. It assumes that someone may be making a synth from photos taken at different times or by different people or that the person shooting may have taken photos of one part of the area, moved on, and then come back to another part for a bit more coverage. Again, it initially only cares about moving through the photos from one image to its nearest neighbor, etc., rather than what order they were taken in.
Nathanael (Over 1 year ago)
If you would like to change this, you can use the [.] and [,] keys to move forward and backward, respectively, through your photos. 

In your case, since your synth is not 100% synthy, the transition when you play through the images in filename order and move from a photo in the main group of 328 to one of the photos in the smaller group of 7 or the two images at the very bottom of Grid View and then back to the photos in the larger group again, the transitions will be very sudden, since they are not linked.

If you would like to change the viewing order for everyone that views your synth, use the 'Edit Synths and Highlights' button, followed by the 'Settings' tab to change the first image that is loaded when someone enters your synth as well as the viewing order. (Selecting 'Slideshow Order: Filename Order' will give you what you are expecting, but will suffer the odd jumps between groups of photos that I describe above.)

Hoping to see more from you in the future.
AZJoe (Over 1 year ago)
Nathanael,  I do not have wrong expectations about the product. I just expect it to synth together things that are obvious.  328 of 337 you say?  It put them together ALL wrong.  Example:  The home image: the 2 outside tables, the image immediately after it and number 15 - 17 BEFORE it are all together and easily stitch together using various photo stitch programs.  Photosynth couldn't figure out that they're related and in fact figured that they belong elsewhere.

My point here is that the logic engine that Photosynth is using to determine "what goes where" leaves a lot to be desired. I never said that they should go through chronologically, but having the ability to tag an image as being related to the right of this other image would help it out.
Nathanael (Over 1 year ago)
Joe, sorry to misinterpret your criticism. In light of the fact that you complained about the order that your photos were in and the viewer jumping from one place to another, I think that my misunderstanding is understandable.

Unfortunately, certain subjects have a steeper learning curve than others in order to create an excellent Photosynth. Wide open airfields with lots of clouds in the majority of the photos is apparently one of them. I did notice that some of the farther shots of the terminal linked the images based on the flags blowing in the wind, rather than the building, which is unfortunate.

It strikes me that you may be criticising the way the current image lays against the background photos. These are arranged so that the movement of the camera movement from one to the next will be as natural as possible, *not* so that it will look like a stitched panorama.
Nathanael (Over 1 year ago)
I looked again at your home image and used both image orders to test the photos before and after that image. The movement of the camera seems perfectly logical to me. Note that I am not saying that the are composited so as to form a cohesive single image. In order to achieve that, generally more photos of a single part of the scene are necessary. 

I'm not quite sure what you mean by "number 15 - 17 BEFORE [the home image]". Do you mean http://tinyurl.com/CGMASH-17 through http://tinyurl.com/CGMASH-15 ? 

In any case, although I think we both agree that the reconstruction algorithms can and will improve, I don't think that what you report is really a bug, but rather your need to learn how to successfully shoot a synth. It matches patches of texture, not objects or outlines objects. To hypothesize where a thing is in space it needs a minimum of three shots of it from three different angles.

More tips here: http://tinyurl.com/psguide8
Nathanael (Over 1 year ago)
Reading over this, I fear I may sound too critical or defensive of Photosynth at the expense of being callous to you.

So, dispensing with criticism, my best advice for anyone on what makes an excellent point cloud (as well as fitting photos more correctly into space) please read the description on my Orbital Propulsion synth here: http://photosynth.net/view.aspx?cid=5f415186-f783-43a2-bd5f-92aa3a9603df

I, like you, originally started with a series of panoramic views but this is not what works best in Photosynth. Instead imagine an inverse panorama using arcs of photos around every interesting bit of the scene. Use regular panoramas combined with paths of photos between objects to link these inward looking arcs which circle the things you care most about in the scene.

Your photos are the computer's first introduction to things. It does not know what buildings look like or aeroplanes or clouds. It needs enough photos of each object in order to understand its shape.
madeeds (Over 1 year ago)
AZJoe: I took a look at your synth and you are right!  The neighbors take you all over the place in the most unintuitive directions.  What's happening here is that photosynth is able to lock on to the beautiful mountains and clouds in the distance to match up your photos, but it's having trouble with the relatively plane asphalt of the runway and limited numbers of shots of any individual airplane.  

I won't say that what you're trying to accomplish with photosynth here is impossible, but it's certainly very difficult.  If you instead try to create a great synth of the building, or a single airplane, you'd be more successful.  

To capture the building, you'll probably need about 100 photos carefully taken around the perimeter at a relatively constant radius.  Then add details: either zoom in, or smaller arcs around things as Nathanael describes.

Good luck!
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