Hi, thanks for making this repo available!
I've been trying to get this to work for a different camera model (cv.omnidir in OpenCV contrib), so I've spent quite a bit of time trying to understand what's going on overall and generating the vector fields. I'm nearly there, but I have a few questions that are still puzzling me. If you can help clear that up a bit, that would be very appreciated.

1. In https://gist.github.com/menandro/b829667f616e72aded373479aca61770, when generating vectorxforward and vectorxbakward, a mix of K0 and D1 is used and that confuses me. I don't understand the paper 100%, but I would have thought the second camera's distortion was already included in the calibration field. Note however, that using any combination of D0,D1,K0,K1 has relatively little impact on the disparity results (aka I've got bigger problems :P)

thetad = theta.*(1 + D1(1)*theta.^2 + D1(2)*theta.^4 + D1(3)*theta.^6 + D1(4)*theta.^8);
...
u1 = K0(1,1) * xprime1 + K0(1,3); % Should be K0 because surface is already corrected

2. In https://gist.github.com/menandro/cd5f4b5309f16f1a0f1987fcb2baf057, the translateScale is not the same in the forward and backward direction. I don't understand the logic behind that. In my case, I used the same scale in forward/backward direction, but using either a scale of 1 or 0.01 also has little impact on disparity maps.

%% Forward direction
translateScale = 1.0;
...
%% Backward direction
translateScale = 0.01;

3. Just to make sure, does the disparity relate to the raw (i.e. distorted) images? (e.g. a given point in the first image at position (u,v) will be at (u+disp.x, v+disp.y) in the second image?). Asking because for the equidistant dataset, the disparities I get are coherent with that. However, both for the t265 "robot" image (Kannala-Brandt model) and for my own data (Mei model), the disparity maps look pretty good in general, but the values themselves seem off. E.g. for a large patch of an image where I expect a x disparity of ~ -40, the results are smooth and coherent, but the disparity is ~ -20. I've tried quite a few variations of parameters (nLevel, fScale, nWarpIters, nSolverIters, lambda, limitRange) and this remains.

4. In https://github.com/menandro/vfs/blob/master/stereotgv/conversion.cu, I don't quite understand how the triangulation is done, but it feels like

	float xprime0 = (u0 - focalx) / cx;
	float yprime0 = (v0 - focaly) / cy;
...
	float xprime1 = (u1 - focalx) / cx;
	float yprime1 = (v1 - focaly) / cy;

Should rather be xprime0 = (u0 - cx) / focalx and so on. Is that correct?