Topics

1

General / Pixel Offset on undistorted photos output

« on: January 27, 2015, 05:26:00 PM »

Hello everyone,

I'm testing Photoscan and the undistorsion it provides on photos used in the calibration process.
I tried to use undistorted photos as input, and I tried to check the option Fix Calibration, so photoscan doesn't undistort the photos when it aligns the cameras.
It never gave me good results.
But when I don't check this option, and allow photoscan to undistort my already undistorted photos, I can see that the result is very accurate.

I'm quite happy with that, but I'm wondering why does Photoscan offset the undistorted photos?

I tried to give distorted photos as input, undistorted photos (with Fix Calibration checked), undistorted photos (without Fix Calibration checked), and in each case, I always have this pixel offset, (even if I have to admit that it's smaller when the input is undistorted).

Can you explain why is that?

Thank you for your help.

2

General / Undistort photos after align?

« on: January 20, 2015, 05:24:00 AM »

Hi everyone,

I'm testing a workflow to scan a set with photoscan, and my friend and I are used to undistort photos before to use them in tracking softwares. To do so, we use Enwaï, a standalone and maya plugin that allows us to use a specific grid of distorsion for our specific cameras, with a lot of options (non linear undistort process, etc..). It's very powerfull and the result is very accurate, so we thought that it could be better to undistort photos before using them in photoscan.

But it seems that it doesn't work well if we give to photoscan undistorted photos to align.

I just want to be sure of the full process you recommend.

Do we just have to give photo (with distorsion) to photoscan, and then export undistorted photos after the align photo process, in order to camera map the model?


If this is the good way to use photoscan, what about your undistort process?
No offense, but I'm sceptical about the full automatic process, is it really as accurate as a process with a specific distorsion reference grid?


C.

3

Python and Java API / Focal length differences in xml and chan export

« on: December 16, 2014, 11:01:47 PM »

Hi,

first sorry for being a rookie.
I have to appologize for my questions, I'm sure that some of you will probably answer them easily and help me.

I'm trying to help a friend who wants to use photoscan in his work but can't import correctly the alignement done in photoscan in another software.
The xml export is very interesting because it keeps bg image informations for each camera (I want to use this), and also the transformation matrix of each cam. But I can't get a correct focal lenght from it.
On the other hand, in the chan export, I have everything i need but the name of bg images for each cam.

So, I'm trying to understand how I can calculate the focal length that is exported in a chan file, from the data that I have in the xml export of the same photoscan alignement. They are differents.
In the xml, I have a focal recalculated, in some units that I don't understand, distorsions factors, etc... and in the chan export, I have just what I need.
But, I can't figure out, how you get the value that is stored in the chan file with some magic formula applied to the values I can get from the xml export.

Can you help me to help my friend?

Thank you,
T.