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Author Topic: Odd Dense Cloud / Masking  (Read 2498 times)

jerry7171

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Odd Dense Cloud / Masking
« on: April 14, 2015, 12:22:59 AM »
I'm photographing a full-sized direct cast bronze copy of Michelangelo's David as a personal challenge to see how well my skills have come along since I started playing with 3D photo-modeling. Here is one of my photos:

https://www.dropbox.com/s/pw2xizj1huld37q/2015-04-12%2017-21-32.JPG?dl=0

As you can see, David is not a good or easy subject since he's dark and surrounded by a visually busy background of trees and cityscape. I used a tripod with my trusty Nikon D3100 set to 100 ISO at f/16 for 2 seconds (so the details of David would come out cleaner and brighter instead of disappearing into a dark featureless mass against the bright overcast sky).

I was able to run the alignment successfully. I then isolated David from the surrounding sparse cloud and erased everything. I shrank the bounding box as closely as possible to the sculpture. I then ran the dense cloud command on a low setting.

My plan was to cheat and let PS do the heavy lifting so I wouldn't have to spend hours masking each photo in Photoshop. I'd rather attempt to raise the Titanic with tweezers than ever have to do that again with another project, especially with something as complex as David. I would make a simple low-resolution model to create the masks from, then start over confident that I'd still saved more time than the old-fashioned masking by hand method.

Except, I go from this:

https://www.dropbox.com/s/p77crn3wb21g7zm/Screen%20Shot%202015-04-13%20at%2015.45.01.jpg?dl=0

to this:

https://www.dropbox.com/s/ze1e8ifa8q75oyw/Screen%20Shot%202015-04-13%20at%2015.45.06.jpg?dl=0

What am I doing wrong? I know all about the "Garbage in, garbage out." theory, but my photos are about as good as I can shoot with my limited knowledge of photography at this point. Am I stuck having to trim away all the excess off the dense cloud before proceeding, or is there a step I missed somewhere?

Thanks!

mrb

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Re: Odd Dense Cloud / Masking
« Reply #1 on: April 14, 2015, 01:06:47 AM »
try building the mesh - I oftentimes find that most of the "sky noise" is filtered out when building the mesh.  Of course, if you don't have any photos of the top of the statue, looking down, I think you're stuck with some white blobs all along the top of his shoulders and head.  Edit it out in a 3D modeling program.

These photo-modeling softwares are still pretty "young", and I simply take it for granted that except for under the most ideal photographing circumstances and conditions, there will be a significant amount of editing by hand needed afterwards.
« Last Edit: April 14, 2015, 01:09:50 AM by mrb »

jerry7171

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Re: Odd Dense Cloud / Masking
« Reply #2 on: April 14, 2015, 03:27:54 AM »
I decided to try out building the mesh, but darn it, I ended up with this:

https://www.dropbox.com/s/wq7b0f78rwns4i8/Screenshot%202015-04-13%2018.12.30.jpg?dl=0

and this:

https://www.dropbox.com/s/44t5stekmh8ald2/Screenshot%202015-04-13%2018.12.05.jpg?dl=0

I decided to put some Family Guy on the television for background noise and I'm attempting to trim away the sky that somehow stuck to the sculpture.

I think most of the problem is not just with the software, but just as much with my inexperience. I've been playing with PS for a while now, but a lot of things I never knew about were learned from other users here and watching a lot of Youtube as well. But half the fun is learning new things as I go.

James

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Re: Odd Dense Cloud / Masking
« Reply #3 on: April 14, 2015, 12:30:44 PM »
You have 145 photos aligned and only 78 depth maps, which means the dense cloud is only being generated from 78 out of your 145 images.

Depth maps are not generated when there are too few matches between photos - you only have 1,455 tie points which is very low.

If you align your images again, under advanced options make sure your tie point limit is high enough. The default is 1000 but i generally set it to 4000.

Then if you get enough matches to generate more depth maps, most of the 'sky' noise should be eliminated, assuming you have a full circle of images around the statue.

bigben

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Re: Odd Dense Cloud / Masking
« Reply #4 on: April 14, 2015, 01:22:39 PM »
Do you have Photoshop? Assuming there is no white in your subject (seems safe for the image you've shown) I run an action to mask out the white automaticallly.
 - colour range selection on white, fuzziness =15 (sometimes increase that depending on the subject)
 - invert the selection
 - create an alpha from the selection
 - save as a TIFF

Then in Photoscan, import masks from alpha.  If there are some images with white in the subject you can edit the alpha for these manually.