问题
I get strange data from solvePnP, so I tried to check it with projectPoints:
retval, rvec, tvec=cv2.solvePnP(opts, ipts, mtx, dist, flags=cv2.SOLVEPNP_ITERATIVE)
print(retval,rvec,tvec)
proj, jac = cv2.projectPoints(opts, rvec, tvec, mtx, dist)
print(proj,ipts)
here opts are 3d points with z=0, detected on this picture:
And ipts are taken from this pic (only part of picture here):
I've checked points themselves (detected with SIFT, points are detected correctly and pairing in a right way).
Now I want to test if rvec and tvec, found by SolvePnP is correct, so I invoke cv2.projectPoint to test if 3d points are projected to the image points. And here is what I have:
So I see that projected points lie outside of image, having y<0.
(retval from solvePnP is true)
This is distortion matrix dist:
1.6324642475694839e+02 -2.1480843988631259e+04 -3.4969507980045117e-01 7.9693609309756430e-01 -4.0684056606034986e+01
This is mtx:
6.4154558230601404e+04 0. 1.2973531562160772e+03
0. 9.8908265814965678e+04 9.5760834379036123e+02
0. 0. 1.
This is opts:
[[ 1708.74987793 1138.92041016 0. ]
[ 1708.74987793 1138.92041016 0. ]
[ 1708.74987793 1138.92041016 0. ]
[ 1708.74987793 1138.92041016 0. ]
[ 1708.74987793 1138.92041016 0. ]
[ 1708.74987793 1138.92041016 0. ]
[ 1708.74987793 1138.92041016 0. ]
[ 1984.09973145 1069.31677246 0. ]
[ 1984.09973145 1069.31677246 0. ]
[ 1908.19396973 1200.05529785 0. ]
[ 1994.56677246 1286.16516113 0. ]
[ 1994.56677246 1286.16516113 0. ]
[ 1806.82177734 1058.06872559 0. ]
[ 1925.55639648 1077.33703613 0. ]
[ 1998.30627441 1115.51647949 0. ]
[ 1998.30627441 1115.51647949 0. ]
[ 1998.30627441 1115.51647949 0. ]
[ 2013.79003906 1168.08728027 0. ]
[ 1972.93457031 1234.92614746 0. ]
[ 2029.11364746 1220.234375 0. ]]
This is ipts:
[[ 71.6125946 11.61344719]
[ 116.60684967 71.6068573 ]
[ 116.60684967 71.6068573 ]
[ 101.60684967 86.60684967]
[ 101.60684967 86.60684967]
[ 116.60684967 101.6068573 ]
[ 116.60684967 101.6068573 ]
[ 112.37421417 53.40462112]
[ 112.37421417 53.40462112]
[ 83.76233673 84.36077118]
[ 98.45358276 112.38414764]
[ 98.45358276 112.38414764]
[ 67.2594223 38.04878998]
[ 96.85155487 51.85028076]
[ 112.26165009 67.25630188]
[ 112.26165009 67.25630188]
[ 112.26165009 67.25630188]
[ 112.24694061 82.24401855]
[ 96.82528687 97.66513824]
[ 112.2511673 97.25905609]]
rvec = [[-0.21890167] [-0.86241377] [ 0.96051463]]
tvec = [[ 239.04461181] [-2165.99539286] [-1700.61539107]]
Also I tried to follow one of the comments and multiply each y from opts by -1, but this gave me even more crazy coordinates outside picture like 10^13.
回答1:
Camera matrix (mts) is incorrect. Fx and Fy are very different (Fx=6.4154558230601404e+04 Fy=9.8908265814965678e+04) and very big. According to comment in OpenCV calibrateCamera() function this problem usually occurs because you have probably used patternSize=cvSize(rows,cols) instead of using patternSize=cvSize(cols,rows) in findChessboardCorners.
来源：https://stackoverflow.com/questions/47723638/output-from-solvepnp-doesnt-match-projectpoints