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Author Topic: Getting Holes...Need More Photos?  (Read 4979 times)

chadfx

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Getting Holes...Need More Photos?
« on: July 03, 2013, 09:13:09 PM »
First time post...how exciting! I just want to start with a huge appreciation to all of you who answer questions so readily in this forum, it is an amazing resource for a great piece of software. So far I've made it through about half of the messages in the forum, lots of helpful info!

I've just starting getting familiar with SfM and Photoscan and have been experimenting with a variety of shooting styles and subjects, mainly with an emphasis for archeological presentation.

I photographed this sarcophagus at a local museum recently, but I am getting some holes and other artifacts in the texture (see right side in screenshot), no matter what method I use for generation (Average, Mosaic / Generic, Adaptive Orthophoto, etc). The geometry is generally coming out okay, but if I choose a higher quality mesh, I start to lose some feature detail, and I'm getting better results with low quality. I shot raw and have boosted the shadows quite a bit, so there isn't much that is dropping into darkness at this point. The photos are a bit noisy, so that could be creating some issues with the solve.

The camera alignment also seems to be okay for all of the photos, as you can see in the screenshot.

My guess is that I need take more photographs from a 3/4 angle along the main length of the sarcophagus in order to get more visual data for the 'nooks and crannies'...and probably try to work at a lower ISO to get the noise down a bit more.

Does that seem like an accurate assessment? Any other thoughts from the brain trust out there?

Cheers, -Chad

Alexey Pasumansky

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Re: Getting Holes...Need More Photos?
« Reply #1 on: July 04, 2013, 11:50:15 PM »
Hello Chad,

"Black holes" in texture usually are the result of insufficient coverage - these black areas are not seen from any photo.

Using minimal ISO is always good, since the noise is minimized, but usually it requires stable shooting from tripod, which is not always allowed in museums.
If you wish, you can share this dataset with our support team, so we could check why you are observing problems with high quality geometry.
Best regards,
Alexey Pasumansky,
Agisoft LLC

chadfx

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Re: Getting Holes...Need More Photos?
« Reply #2 on: July 05, 2013, 01:10:54 AM »
Thanks for the tips, Alexey. I am going to try to re-shoot this over the weekend and see if I can get a better result. I agree that the black holes are likely from me not capturing a direct angle into those recessed spaces.

I'll try to stabilize the camera a bit more so I can use a lower ISO as well...maybe I can sneak in a monopod. ;-)

I'll try to follow up with the improved results.

Thanks again, -Chad

chadfx

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Re: Getting Holes...Need More Photos?
« Reply #3 on: July 06, 2013, 03:06:17 AM »
Follow up:

I found a neat trick to get rid of the black holes in the texture via an older forum posting from Lee...export the texture and re-import it. Worked exactly as hoped.

Is this an undocumented 'feature'? ;-)

http://www.agisoft.ru/forum/index.php?topic=446.0;prev_next=next#new

ps. and cheers, Lee...very helpful tip!

pps. I've seen various forum postings about trying to add to the documentation or produce more tutorial videos, but have not seen any actual outcome...is it possible to start adding some of these tips and gotchas into the wiki pages at least? I think about half of what I've learned so far has come from this forum.