The extrinsics configuration file (extrinsics.ini) is a simple text file used for specifying the extrinsics between the cameras:

phi = 0
theta = 0
psi = 0
T1 = 1
T2 = 0
T3 = 0

The coordinate system is aligned with the optical center of the left camera and is denoted with the figure above.

The extrinsics describe the pose of the left camera relative to the right camera, described by the rotation matrix $R$ and a translation vector $\vec{T}$.

The rotation matrix $R$ describes the rotation of the left camera with respect to the right camera and is assembled following $xyz$ rotation order — $R = R_{\psi}R_{\theta}R_{\phi}$, where the angles $\phi$ (along x-axis) , $\theta$ (along y-axis), $\psi$ (along z-axis) denote Euler angles around their respective coordinate axes. In other words, the resulting $R$ rotates the axes of the right camera to align with those of the left camera where the left-camera axes are represented in the right camera coordinates.

phi: Denotes the pitch or Euler angle of the left camera in degrees around the x-axis relative to the right camera

theta: Denotes the yaw or Euler angle of the left camera in degrees around the y-axis relative to the right camera

psi: Denotes the roll or Euler angle of the left camera in degrees around the z-axis relative to the right camera

The translation vector $\vec{T} = (T_1, T_2, T_3)$ is expressed in the right camera’s coordinate system and describes the translation of the right camera relative to the left camera.

T1: Translation in x-direction

T2: Translation in y-direction

T3: Translation in z-direction

You can perform the Initial Calibration routine to get the initial extrinsic parameters between the cameras.