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Author Topic: Best practices for tank scanning  (Read 21994 times)

tarkhil

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Best practices for tank scanning
« on: March 05, 2015, 11:01:23 PM »
Hello!

I'm going to scan a tank with AgiSoft's PhotoScan

As far as I understand, it requires about 400-500 photos to make a good model of such an object.

I understand that photos should be made from several heights, and with good overlapping; but should I try to stay close to object or far enough to fit all object into viewfinder?

Maybe some other best practice recomendarion?

igor73

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Re: Best practices for tank scanning
« Reply #1 on: March 06, 2015, 04:04:41 AM »
Some basic guidelines.


  • at least 50% overlap both horizontal and vertical
    Do not try to get the whole tank in the image.  Go closer instead.   
    Use good imaging  technique.sharp images, even lighting,  low ISO and good DOF. 
    Think 3D, you ned parallax and angels to build 3D
    All set for awesome results.




Marcel

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Re: Best practices for tank scanning
« Reply #2 on: March 06, 2015, 11:54:03 AM »
What kind of tank? One with a cannon on top or an oil storage tank?

Use a tripod and make well exposed and sharp images. Sound simple right :)

Show us the results, I am very curious how it turns out!

tarkhil

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Re: Best practices for tank scanning
« Reply #3 on: March 06, 2015, 12:35:47 PM »
For sure I'll do! Yes, it will be a tank (with some luck, LOTS of tanks) with cannons and mgs and everything else.

tarkhil

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Re: Best practices for tank scanning
« Reply #4 on: March 06, 2015, 09:48:58 PM »
I haven't yet try the tank, but I'm training on a nearby trailer. With 123 photos, it looks fairly good, but crumpled a lot.

What can be done besides manual editing?

igor73

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Re: Best practices for tank scanning
« Reply #5 on: March 06, 2015, 11:56:07 PM »
If you post some example images maybe someone can help you

tarkhil

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Re: Best practices for tank scanning
« Reply #6 on: March 07, 2015, 10:19:04 AM »
https://drive.google.com/folderview?id=0B2oEX4lg2uEtWFM5eGlsZEs2OE0&usp=sharing

NEFs, processed jpegs, project - everything are there./ Thanks in advance.

Marcel

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Re: Best practices for tank scanning
« Reply #7 on: March 07, 2015, 01:06:07 PM »
The "Airstream" trailer is not an ideal test subject. It has lots of reflections, and hardly any usable surface detail for Photoscan to determine the surface shape. Apart from the seams and rivets, it's all flat and smooth. Try finding something that is dirty and old, like a statue or a really old and dirty car.


Your photos have a lot of noise because your camera was at ISO2200. For better results the photos need to be as noise free as possible.

To improve the quality of your photos:

- put your camera on a tripod
- use a low ISO (ISO100)
- camera in A (Aperture) mode with the Aperture between F8 and F11
- use a remote release cord (so you don't move the camera while pressing the shutter button)
- when you convert from NEF to JPG, save at the highest possible setting (JPG Quality 12 in Photoshop).

Using JPGs is fine, but you have to save them with the highest possible quality to prevent compression artefacts.

Your photos are all more or less at eye height, with the camera pointing down for parts of the trailer that are low to the ground. Using multiple rows of photos will give better results (high, medium, low). So put your tripod at the highest position for the top row, at medium position for the middle row, and at very lowest for the bottom row. That way the camera position changes, which will make it easier for Photoscan to do an accurate reconstruction.


tarkhil

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Re: Best practices for tank scanning
« Reply #8 on: March 07, 2015, 08:39:57 PM »
Ok, I knew about ISO, but I didn't have a tripod at hand. I'll go for a tank tomorrow, and will try my best

Marcel

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Re: Best practices for tank scanning
« Reply #9 on: March 07, 2015, 10:42:14 PM »
I strongly advise to get a tripod (and a remote release cable). For good quality photos you need to use a low ISO, and you cannot handheld photos at those shutterspeeds.

tarkhil

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Re: Best practices for tank scanning
« Reply #10 on: March 09, 2015, 01:22:30 PM »
Okay, I've made a next attempt. T-34 near Soviet Army museum, ISO 400 (working one for D300s), as many good photo as was possible trying not to fall off.

In some 15 minutes, at same link, I'll post my results.

tarkhil

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Re: Best practices for tank scanning
« Reply #11 on: March 09, 2015, 06:04:11 PM »
It took quite a time! Right now I have a dense cloud, which looks pretty much like a tank

Marcel

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Re: Best practices for tank scanning
« Reply #12 on: March 10, 2015, 11:13:49 AM »
Screenshots or it didn't happen  ;)

bigben

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Re: Best practices for tank scanning
« Reply #13 on: March 10, 2015, 12:18:39 PM »
I had a quick play with some of the images. In general I'd say that the camera angle tends to jump around a bit, and in some cases there aren't really enough images to provide adequate information of the detail of the tank that you focused on.  I'd suggest trying to be more methodical in your approach to taking the images. Whilst it's not entirely necessary, it helps when you're starting out to have each image overlap part of the previous image. Focus on getting an overall set of images for the tank and then move in on specific details and you should find it easier to get a good result.

tarkhil

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Re: Best practices for tank scanning
« Reply #14 on: March 10, 2015, 04:46:06 PM »
Okay, here is a part of tank processed with medium quality. I'm expecting 8 Gb more RAM today.