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Author Topic: Reliance on "features" are too restrictive  (Read 6878 times)

ozRocker

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Reliance on "features" are too restrictive
« on: June 15, 2015, 01:52:05 AM »
I know photogrammetry works by feature matching, which is the same as panorama.  However, I'm finding this restriction is a real burden.  Scans where a person is wearing black leather boots, or items of clothing that is a plain colour end up with too much missing topology info.  Even large areas of clear skin cause problems.  I'm wondering how other people are dealing with this problem, or are they just giving their customers a list of things they cannot wear and also patching up holes in post-production?  I'm aware that a projection system can help solve this problem but it would effectively halve the shutter speed, or worse.
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FoodMan

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Re: Reliance on "features" are too restrictive
« Reply #1 on: June 15, 2015, 03:54:03 PM »
I think the answer is in your question..

 :)

ozRocker

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Re: Reliance on "features" are too restrictive
« Reply #2 on: June 16, 2015, 11:43:13 AM »
ok, what I really want to know is if there is a solution that doesn't involve using a projection system.  For example, what would be the best way to scan someone wearing a black suit?
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FoodMan

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Re: Reliance on "features" are too restrictive
« Reply #3 on: June 16, 2015, 04:55:54 PM »
a black suit..? well I'd say white light scanner can do it, although that's a different story... but for photogrammetry, no distinctive features = no scan, or a bad scan at best. so yes projection is the only known way of doing it.. or powder talc, with some cleaning to do..  :P


ozRocker

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Re: Reliance on "features" are too restrictive
« Reply #4 on: June 18, 2015, 12:33:45 PM »
I like the talcum powder idea!  :D
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Tyler J

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Re: Reliance on "features" are too restrictive
« Reply #5 on: June 19, 2015, 04:44:51 PM »
One solution would be to use a photogrammetry software used specificaly for human (I don't know any)
If the software knew what a human is suposed to look like and use that (nose, mouth, eyes, ears, chin, etc) to match the pictures then it would be much easier.


vfxman222

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Re: Reliance on "features" are too restrictive
« Reply #6 on: June 20, 2015, 03:30:53 AM »
I'm wondering how other people are dealing with this problem, or are they just giving their customers a list of things they cannot wear and also patching up holes in post-production?
Yes, a spec sheet of acceptable materials is given to client, and yes to the other. There will ALWAYS be cleanup after the scan is processed. Hole filling, bump smoothing, texture cleaning, etc....

For some darker fabrics, as shown in this scan I did (https://vimeo.com/104762987), you need high resolution, lots of even clear light, and sharp deep depth of field. You also need to always shoot RAW. Having RAW images can buy back some flexibility when processing the images. For the above scan, and most scans for that part, I run a pre-process of all of the images to brighten the shadows and bump up the exposures without clipping the details, run through Agisoft and once I have a decent mesh, I then swap the images out for more normal exposed versions to then process the texture pass.
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Wishgranter

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Re: Reliance on "features" are too restrictive
« Reply #7 on: June 20, 2015, 11:37:50 AM »
try to go with RAW capture of dark stuff. if have something in RAW send me the data and will show how can solve it. but when its a 100 % black, low light conditions and etc, it cannot be solved... its about how photogrammetry work...
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ozRocker

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Re: Reliance on "features" are too restrictive
« Reply #8 on: June 22, 2015, 12:13:09 PM »
I never use the raw files, but now I will.  Thanks for the great tips! :D
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