Forum : Bugs

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


Topic: Double (ghost) Point cloud

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lostinthetriangle (Over 1 year ago)
I have been seeing double point clouds since I started using photosynth. In normal mode the photos look ok, but as soon as you press p for the point cloud sometimes a double (ghost)image appears. 
In this one of "Carter House" you can really see the double "ghost" cloud, the front steps especially.

http://photosynth.net/embed.aspx?cid=2a99a128-b8e4-48d1-9ffa-31a23cefbc1c

Just wondering what I am doing to get this effect? Or what do I do to get rid of it. I tried taking out some of the pictures that I thought where the problem, but that did not work.
bitplane (Over 1 year ago)
strange problem. looks like the leftmost image of the bush halo is responsible for most of those points, but the path is disjointed too. 
The only thing I can suggest is to try adding some more images around the steps and the path, see if it can get a better fix on it
lostinthetriangle (Over 1 year ago)
bitplane, I think I know what might be causing this..............When I have some time I need to shoot something small and then try to force the same effect.
bitplane (Over 1 year ago)
argh! I've got the same problem with my megasynth-
http://photosynth.net/view.aspx?cid=e8a88c92-7d22-4b3c-b490-1d8fa160583c

I think this shows that it's not a problem with not enough pictures!

Making a test case that reproduces the problem with minimal data is the right way to go, it will certainly give the guys at Microsoft a head start. I'll try investigating myself.

Good luck!
EdLee (Over 1 year ago)
I don't know the math or algorithms behind the synther, so PS people can tell about this theory: it IS a problem of not having enough photos. For example:

http://photosynth.net/view.aspx?cid=c8063fc8-145b-4b42-936f-58ca7724b26d

If you rotate the building so you are looking down at the staircase and the 2nd floor hallway from the top, you'll see they don't align with the outer walls of the building and the tunnel. I don't have the building's blueprint, but I am guessing in reality, the staircase and the hallway align perfectly with the building walls. The reason they don't in the Point Cloud is that the synther does not have enough information.

In the Carter House synth, imagine if the steps are NOT fixed but are actually MOVABLE in real life. Then it's obvious how you can achieve the ghost effect.
It's like the ghost points from living or non-living things that move. If you have more photos to cover the steps, I think the 2 ghosts will merge and the effect gone.
lostinthetriangle (Over 1 year ago)
EddLee, I see what you mean about the staircase. Bit cockeyed!
And I think you are correct about the program not having enough "information"
That photosynth can take a 1000 pictures and match the inside to the outside is in itself pretty amazing!
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