search

ethz-asl / kalibr

The Kalibr visual-inertial calibration toolbox
Other
4.39k stars 1.41k forks source link

Extrinsic transformation matrix (T_cn_cnm1) #408

Closed malleshamdasari closed 2 years ago

malleshamdasari commented 3 years ago

Hi, I am trying to calibrate a Stereo camera and confused about the transformation matrix (T_cn_cnm1). In the description, it is given that "_camera extrinsic transformation, always with respect to the last camera in the chain (e.g. cam1: T_cn_cnm1 = T_c1c0, takes cam0 to cam1 coordinates)". I need a transformation matrix from the other way i.e., say T_cn_cnm0, where the transformation should be with respect to the first camera (e.g. cam0: T_cn_cnm0 = T_c0_c1, takes cam1 to cam0 coordinates).

I just multiplied the translation vector (i.e., 4th column) with -1. It is working somewhat close to what I expected. However, I am not sure if this is the correct way. Do I have to do something for the rotation matrix as well? Thanks.

ynma-hanvo commented 3 years ago

mulitply by -1 with the translation is the same as inverse() result , so u can inverse first, then use the translation part; stereo camera are supposed to have no rotation between left and right ( am I right ?); so i guess no need for rotation matrix ;

ynma-hanvo commented 3 years ago

mulitply by -1 with the translation is the same as inverse() result , so u can inverse first, then use the translation part; stereo camera are supposed to have no rotation between left and right ( am I right ?); so i guess no need for rotation matrix ;

goldbattle commented 2 years ago

This has some details if you are not familiar with frame transformations: https://ingmec.ual.es/~jlblanco/papers/jlblanco2010geometry3D_techrep.pdf