Forum

Author Topic: Build Geometry subsampling  (Read 4485 times)

patcarbon

  • Newbie
  • *
  • Posts: 22
    • View Profile
Build Geometry subsampling
« on: October 16, 2012, 04:14:17 PM »
Hi,

I can't find this in the wiki or older posts.  What level of subsampling occurs at Ultra high, high medium and low geometry builds?

I think Ultra uses the raw image resolution and high uses a 2X2 pixel average.  but what about medium and low?  These things should go in the wiki.  It's quite usefull to know if you have an idea of the raw image resolution and you have an idea of the final average point cloud/DEM resolution you need.

Wishgranter

  • Hero Member
  • *****
  • Posts: 1202
    • View Profile
    • Museum of Historic Buildings
Re: Build Geometry subsampling
« Reply #1 on: October 16, 2012, 07:46:39 PM »
ULTRA - 1x1 px
HIGH - 2x2 px
MEDIUM - 4x4 px
LOW - 8x8 px
WLOW - 16x16 px....

every step use aprox 8 times more RAM and CPU resources, best if use HIGH, medium for larger projects.... ULTRA is very demnading on all resources...... 
----------------
www.mhb.sk

Dino

  • Newbie
  • *
  • Posts: 32
    • View Profile
Re: Build Geometry subsampling
« Reply #2 on: October 16, 2012, 07:52:05 PM »
So basically resized photos (half Mpx) in ultra high is the same as full res photos in high? Did I got it correctly?

Wishgranter

  • Hero Member
  • *****
  • Posts: 1202
    • View Profile
    • Museum of Historic Buildings
Re: Build Geometry subsampling
« Reply #3 on: October 16, 2012, 08:00:25 PM »
Not exactly, im have still some open questions there, becasue it seems that it do not RESAMPLE in averanging pixels, but much more use just every n-th pixel.....

Im, do resampling sometimes, from 18 Mpix to cca 8 Mpix and can reconstruct on ULTA/HIGH more images = precise model..

Agisoft team could explain it better :-)
----------------
www.mhb.sk

Alexey Pasumansky

  • Agisoft Technical Support
  • Hero Member
  • *****
  • Posts: 13916
    • View Profile
Re: Build Geometry subsampling
« Reply #4 on: October 17, 2012, 01:33:52 PM »
Hello,

Using lower geometry quality settings scales the original images averaging the neighboring pixels, so processing original images in High would give similar result as if the 2xdownscaled images are processed in Ultra.
However, please note that photo alignment has the same behavior (original with Medium accuracy is nearly equal to 2xdownscaled in High).
Best regards,
Alexey Pasumansky,
Agisoft LLC