The relationship between fisheye image and cube image

[ZhouXiner]

When building map relaitionship between fisheye image and cube image, the fuction "CubemapToFisheye", I notice that the related beadring vector of (u,v) in fisheye image will be evaluated by: i = i - static_cast(i / mWCubeFace) * mWCubeFace; j = j - static_cast(j / mHCubeFace) * mHCubeFace; x = (i - cx) * z / fx; y = (j - cy) * z / fy;

Why cant we just use function "ImgToWorld" to evaluate the bearing vector. Thanks