What are the "maps" returned by the initUndistortRectifyMap() function?

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Hello everyone,

I need to calibrate 2 cameras in order to do some image processing (stereoscopy). For that I use the function initUndistortRectifyMap() which returns 2 "maps", after calling stereoCalibrate() and stereoRectify() . What do these 2 maps represent ?

My initial guess, was that they represent transformation maps used to transform every pixel of an image with the remap() function. However, if this was the case, why would there be 2 maps returned by the function ?

Thank you.