AliceVision [calibration] Camera calibration format

[calibration] Camera calibration format

Open simogasp opened this issue 8 years ago • 12 comments

Decide the format to use for the camera calibration file. Note that we must be able to deal with:

a camera with fixed intrinsics parameters
a camera with intrinsics parameters changing over time (f, pp, and k3)
a camera rig composed of N (N = {1,2,3}) cameras

So far for the camera localization (voctree or cctag based) a simple txt file is used using a format like this

// the structure of the file is
// int #image width
// int #image height
// double #focal
// double #ppx principal point x-coord
// double #ppy principal point y-coord
// double #k0
// double #k1
// double #k2

as explained here https://github.com/poparteu/openMVG/blob/voctree_localizer/src/openMVG/dataio/IFeed.cpp#L18

Oct 22 '15 13:10 simogasp

Why not directly use the cereal serialization of the existing camera class

Oct 22 '15 14:10 pmoulon

yes, the json it's the natural and obvious solution, but we need to define how to deal with a video stream in which the camera calibration is changing over time. So we need something like frame ID -> camera calibration, for each frame or just whenever it changes. I don't know

Oct 22 '15 14:10 simogasp

The SfM_Data format already support that. Why not create a sfm_data file for the video, with different intrinsic for each frame. So you save, load it for an entire video...

Oct 22 '15 14:10 pmoulon

yes, the thing i forgot to mention (i will added to the description) is that we deal with a rig of 3 cameras. So we need to take also that into account. (ie one of the camera may change the parameters while the other does not). BTW did you do anything to deal with a rig of cameras, ie like a class modeling the rig or other?

Oct 22 '15 14:10 simogasp

In the SfM_Data class to make some intrinsics shared or not, so you can do whatever you want.

Regarding the rig: I have started a functional draft here: https://github.com/pmoulon/openMVG/blob/develop_rig_subposes/src/openMVG/cameras/Camera_Pinhole.hpp#L136 In which you must update the subpose with known data.

Additionnaly a RigView concept have been created: https://github.com/pmoulon/openMVG/blob/develop_rig_subposes/src/openMVG/sfm/sfm_view.hpp#L73 The idea is to store additional info like the RIG id & subchannel id

Oct 22 '15 14:10 pmoulon

cool, that could be useful. If i understand correctly a rig is composed of several Rig_Pinhole_Intrinsic, each having a subpose wrt some reference camera. And then in sfmdata each view is like a normal view but it also contains the reference to the rig ID (in case there are several rigs) and an its internal ID inside the rig

Oct 22 '15 15:10 simogasp

You got it. I think it was a flexible solution. The other solution was to make all intrinsic have a subpose and let it bet Id by default (but this solution impose to check always if the subpose is Id or not). I have preferred to make a new class first to test and ensure that the design fit the needs.

Oct 22 '15 15:10 pmoulon

Ok thanks!

Oct 22 '15 15:10 simogasp