Camera pose from VisualSFM camera_v2.txt file

0
votes

I am new to visualSFM and Computer Vision. I am wondering how I can compute the camera pose (the direction in which the camera is looking) with respect to the world coordinate system and also the camera location with respect to the world coordinate system. The output in camera_v2.txt file is as follows:

  • The format of each camera is as follows:
  • Filename (of the undistorted image in visualize folder)
  • Original filename
  • Focal Length (of the undistorted image)
  • 2-vec Principal Point (image center)
  • 3-vec Translation T (as in P = K[R T])
  • 3-vec Camera Position C (as in P = K[R -RC])
  • 3-vec Axis Angle format of R
  • 4-vec Quaternion format of R
  • 3x3 Matrix format of R [Normalized radial distortion] = [radial distortion] * [focal length]^2 3-vec Lat/Lng/Alt from EXIF

Am I right in assuming that C is the position of the camera with respect to world coordinates. In that case what is the direction in which the camera is looking.

1
computer-vision

1 Answers

0
votes

'R' and 'T' (or commonly denoted as 't') are the extrinsic camera calibration [R|t]. Camera center in 3D coordinates is given by -R^-1 * t = -R^T * t (R^T is the transpose of R). R is the rotation matrix that can be given in (Rodrigues) angle axis, quaternion or plain 3x3 matrix format; it indeed expresses how the camera is oriented in 3D space. Watch out how the 3D Y- and Z-axis are chosen, different options exists.