Why does the shock coefficient have 4 parameters, shouldn’t it be 5?

[sumenpuyuan]

Why does the shock coefficient have 4 parameters, shouldn’t it be 5?

[sisyphus-99]

We use the initUndistortRectifyMap in opencv to undistort the image. The order of the distortion coefficients is consistent with the input requirement of this function:

Input vector of distortion coefficients:
[k1,k2,p1,p2,k3,k4,k5,k6,s1,s2,s3,s4,taux,tauy] of 4, 5, 8, 12 or 14 elements. 
If the vector is empty, the zero distortion coefficients are assumed.

reference link: https://amroamroamro.github.io/mexopencv/matlab/cv.initUndistortRectifyMap.html