Topic: Point Cloud Background

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pope_luke (Over 1 year ago)
This is really something simple that's been bothering me for quite some time. The background color within the photosynth viewer is always black. Usually this is perfectly fine, but sometimes it causes trouble, specifically when you are taking photos of black things. I made an admittedly poor synth of a black guitar which, in the point cloud, became transparent. I have the suspicion that even though I can't see the black points, they must be there, since other colored points seem to disappear when moving behind them.
I also viewed a wonderful synth recently of a dead tree. While the trunk was brownish and had a rich point cloud, the black branches were no where to be seen.

The suggestion that I'm making is whether we could have a simple button to change the black to white, or a few other color options? Though I don't see why other colors would be more useful... then again, blue would have been nice if I had wanted to see the branches well against the sky...
Nathanael.Lawrence (Over 1 year ago)
While I would find the option to change the background color useful, I don't believe that there are actually any black points in your guitar synth. If there are any they must be very few indeed. In your description you wonder aloud if it's just too shiny to produce a pointcloud and I would have to say that that is exactly what I think happened.

I think that the black backdrop, apart from drawing out the color of the pointcloud is really a throwback to novels like Snow Crash and the like. I know some of the guys on the Photosynth team see Photosynth as the beginning of true cyberspace, hence the black void backdrop.

If you look at Photo Tourism project (the research that Photosynth grew out of) they nearly always use a white backdrop for their pointclouds.
pope_luke (Over 1 year ago)
I suppose I should have linked the actual example I was thinking of, since my synth is pretty bad.

The light blue sky gets points, but the branches don't, making it seem in the cloud as if the tree is flowering. (Considering the actual state of the tree, I guess that's a bit amusing now that I think about it.) What's happening with the black here?

I understand the value and effect of a black background, though. It makes sense as a default that the cloud appear out of nothing, rather than just being plopped in a blank white world. Black suggests unknown space in a more intuitive way.
Nathanael.Lawrence (Over 1 year ago)
Although, in defence of white voids, there is The Construct scene in the original Matrix movie.

As for the sky problem around leaves and the smaller branches, you caught me. :) I'm thinking that could be fixed by a better understanding of my camera. The 'Auto' setting was adjusting the exposure so that many of those upper branch shots had a decent shot of the cloudy sky, but the branches were underexposed, leaving no real texture for Photosynth to work with. Also, in the above and other cases, since the photos that Photosynth works with are, after all, just coloured points in a grid, when enough photos are taken around the space where two small branches meet, it interprets that sky as a blue or grey object with a pointy corner.

Here are other examples of the sky point cloud around the edges of leaves:
Nathanael (Over 1 year ago)
I was thinking of this back when Nathan Craig first pointed me to Christoph Hausner's Photosynth Pointcloud Exporter (since renamed to SynthExport at ), but if you're really curious you can export your pointcloud and view it in Meshlab (available for free here: ). 

In Meshlab, you can set the background color to whichever two colours you prefer so if you want to check for black points, you could set both background colors to white and see what shows up.