Forum

Author Topic: Where am I going wrong  (Read 9992 times)

casper

  • Newbie
  • *
  • Posts: 4
    • View Profile
Where am I going wrong
« on: July 13, 2012, 09:44:08 PM »
Hi there,

Having some trouble getting any kind of decent results from my scans. I've read the manual and scanned the forum for tips, but I'm still not having much luck. My geometry generally ends up very messy.

I'm using a single camera, Nikon D90, 12MP, wide lens, f/8ish, 1/200. I've tried everywhere from 10 - 80 photos. Specifically, I'm trying to do a simple head scan, taking photos around a 180 degree ark. Here are some samples of the photos I've been using. I'm using the general align and mesh parameters put forth in the PDF tutorials.

I have seen some pretty good results from people scanning heads with a single camera, so I'm wondering why my results are so inferior!

Any general tips or advice would be greatly appreciated!

Thanks.






FoodMan

  • Sr. Member
  • ****
  • Posts: 477
    • View Profile
Re: Where am I going wrong
« Reply #1 on: July 14, 2012, 10:41:55 AM »
hard to say without seeing you result...

Wishgranter

  • Hero Member
  • *****
  • Posts: 1202
    • View Profile
    • Museum of Historic Buildings
Re: Where am I going wrong
« Reply #2 on: July 15, 2012, 01:57:58 PM »
wide lens - what mm range ?
----------------
www.mhb.sk

casper

  • Newbie
  • *
  • Posts: 4
    • View Profile
Re: Where am I going wrong
« Reply #3 on: July 15, 2012, 07:37:00 PM »
Around 18 - 24mm on a APS-C sensor, so 27 - 36 as a 35mm equivalent

Attached is a sample of my results. Thanks in advance!


Alexey Pasumansky

  • Agisoft Technical Support
  • Hero Member
  • *****
  • Posts: 11247
    • View Profile
Re: Where am I going wrong
« Reply #4 on: July 15, 2012, 07:53:40 PM »
Hello Casper,

And could you please provide a screenshot of reconstructed camera positions with point cloud view?
Best regards,
Alexey Pasumansky,
AgiSoft LLC

casper

  • Newbie
  • *
  • Posts: 4
    • View Profile
Re: Where am I going wrong
« Reply #5 on: July 15, 2012, 08:17:43 PM »
Hi Alexey

Here is a setup I used with roughly 18 camera positions. This time, as you can see, after camera align, it did not generate points on the hair. Why would this be? On previous attempts the hair was fine. I even underexposed so the blonde hair didn't get blown out on the highlights. Any ideas?


FoodMan

  • Sr. Member
  • ****
  • Posts: 477
    • View Profile
Re: Where am I going wrong
« Reply #6 on: July 16, 2012, 08:41:00 AM »
well all I can say is that the hair is overexposed where you see no points... Pscan hates overexposed photos.. it can't find any reliable points..

as for the strange shift you see in her face, I'd say the model moved a bit between shots... I know it is very hard to stand still for 18 photos... just breathing makes the model move..

This is why for alive subjects, a multi-cam setup is highly recommended..

my 0.2 cent...
f/

Wishgranter

  • Hero Member
  • *****
  • Posts: 1202
    • View Profile
    • Museum of Historic Buildings
Re: Where am I going wrong
« Reply #7 on: July 16, 2012, 01:10:58 PM »
See the http://www.agisoft.ru/forum/index.php?topic=411.0 for more info.

go to the CHUNK and read the info about REPROJECTION ERROR and write it here. What setting you have on the GENERATE MESH menu ?

 try it with HIGH or ULTRA and post the screenshot......
----------------
www.mhb.sk

casper

  • Newbie
  • *
  • Posts: 4
    • View Profile
Re: Where am I going wrong
« Reply #8 on: July 16, 2012, 04:16:00 PM »
Thanks Wishgranter and Foodman.

She just dyed her hair again so I guess that's why it couldn't be picked up. Stupid blondes!

I have been getting better results with high and ultra-high in the mesh settings. Unfortunately I'm using a laptop with 8GB of RAM, so I can't use too many photos or too high settings, as the application runs out of memory.

The project I am working on is an art installation so it doesn't matter if the mesh isn't totally perfect. In fact the errors in the mesh are part of what makes this fascinating. We have a series of 3D scanners at my University, but their results are shocking in comparison. Really having fun with this. Agisoft should make student licenses available.

I'm very interested to see how good the results can be from a single camera. I am just blown away with this software in general. Multicam would be really fun, but for now I am a poor student so one will have to do.

Thanks again. Will post further progress.

FoodMan

  • Sr. Member
  • ****
  • Posts: 477
    • View Profile
Re: Where am I going wrong
« Reply #9 on: July 16, 2012, 04:37:47 PM »
.... maybe try with the person laying down.... MarkFlorquin has some amazing results, and he used one camera too...

http://www.agisoft.ru/forum/index.php?topic=411.0

Alexey Pasumansky

  • Agisoft Technical Support
  • Hero Member
  • *****
  • Posts: 11247
    • View Profile
Re: Where am I going wrong
« Reply #10 on: July 16, 2012, 04:57:26 PM »
Hello Casper,

Looks like the problem is in wrong camera alignment that could be caused by slight motions of the person or breathing.
So the shooting session of a person if only a single camera is used should be carefully planned and also a person should stand still, so maybe sitting in a chair and fixing neck with the head could improve the alignment and reduce unwanted motions.
Another tip is to use masks and "Constrain features by mask" option at Align Photos stage, it will help if the head was moving during the shooting. But better of course is to prevent such movements than to work with their consequences.

Also the problem with too little points on the face could be caused by too much points detected on the background, since the skin is not so textured as wooden background is.
Best regards,
Alexey Pasumansky,
AgiSoft LLC