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Author Topic: Scanning objects fully without any occlusions  (Read 4080 times)

calidos

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Scanning objects fully without any occlusions
« on: December 21, 2013, 03:29:03 PM »
Hi all,
This is my first project in Photogrammetry, and I'm an absolute beginner so apologies if it's a trivial question.

I am working to define a strategy to capture all the pieces of a broken sculpture (around 100 fragments) which can be seen here http://www.calidos.cat/fotogrametria/crbmc/jacent_m.jpg
each piece must be completely defined as part of restoration documentation.

Now to, prepare workflow, I did a set with a turntable, on a white or green background and 4 light softboxes. If I set a fragment on the turn table I obviously have a lot of occlusion so I made a wooden support (10x10x10cm) and 4 small metal cylinders to prop up the piece a bit higher.
After some testing I have obtained some reasonable results (using 40 photos in three different levels)
http://www.calidos.cat/fotogrametria/crbmc/test.jpg

However, there are still some undesirable artifacts such as tiny shadows and the 4 holes. I'm trying to optimise this method and I would love to know if anyone has any ideas of how to do this in a more efficient or accurate manner. For instance, would there be a way to turn the piece around and process it in the same project?

Thanks in advance,

Josep
calidos.cat

FoodMan

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Re: Scanning objects fully without any occlusions
« Reply #1 on: December 21, 2013, 06:56:44 PM »
a few advices ..

_ use a green background, it will be easier to make an alpha
_ no need of support.. do a full turnaround, then turn the piece to scan upside down, and do another turnaround, this will limit the occluded parts. so around 80 photos per piece.
_ try to scan all pieces using the same distance... so scan the biggest piece, and then block the cam distance from other pieces, otherwise you might end up with too high def small pieces, and lower def big pieces, I guess you want to keep the same definition for all pieces..

my 0.1 cent  :)

calidos

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Re: Scanning objects fully without any occlusions
« Reply #2 on: December 22, 2013, 02:23:33 AM »
Thank you very much FoodMan!
I did as you indicate and is perfect.
I used a blue background (chroma) because if I need to scan white marble pieces I think color is too close to gray to do the mask.
The problem coud be to unify so diferent sizes: 50 cm some parts and 5 cm small ones.
If I fix the camera for all shots maybe small fragments will have so small pixels to stich them.
I'll try to do some more test first.

Best wishe and Merry Christmas!
josep
calidos.cat

calidos

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Re: Scanning objects fully without any occlusions
« Reply #3 on: December 22, 2013, 02:55:01 AM »

FoodMan

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Re: Scanning objects fully without any occlusions
« Reply #4 on: December 22, 2013, 10:47:19 AM »
hey so far so good..   8)

well regarding the size consistency, what I would do is to first scan the smallest piece and largest piece and try to find a good balance (distance from Camera)..

f/