Reconstructing 3D from some images without calibration?
3d-reconstruction, c++, opencv
Solution
The calibration grid (chessboard in the typical OpenCV example) is simply an object of known dimensions that lets you estimate the camera's intrinsic parameters, i.e. the mapping from camera coordinates to the image coordinates of a point. This includes focal length, centre of projection, radial distortion parameters et cetera. If you do away with the calibration object, you will need to find these parameters from the image observations themselves. This approach is called "self-calibration" or "auto-calibration" and can be fairly involved. Basically, you are trying to get a good starting point for the follow-up non-linear optimisation (i.e. bundle adjustment). For a start, you might want to refer to Marc Pollefeys' PhD thesis, who came up with a simple linear algorithm for this problem: http://www.cs.unc.edu/~marc/pubs/PollefeysIJCV04.pdf
Problem
I want to make a 3D reconstruction from multiple images without using a chessboard Calibration. I'm using OpenCV and studying the method to obtain the way to get the model 3D from 30 images without calibrating the camera with a chessboard pattern. Is this possible? Where can I get the extrinsics params? Can I make the 3D reconstruction without calibrating?