3d image reconstruction from a 2d image (a bottle pointing from 2d to 3d)

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Hello Everyone

I am working on a spin the bottle game with OpenCV and a robot NAO. I already made a program to draw a line projecting to the pointing place of the bottle but in 2d (the robot can see just the bottle in a white background) now I would like with opencv to project that line into the 3d space in order to find a person which the bottle points to.

I am not sure how or where to start. I found something with camera calibration, Pose estimation and Depth Map from Stereo Images. Could you guys please help me with information or topics where I could start reading or doing something from OpenCV?

Thanks