Real World Points [X Y Z] determination (VISION)

The imagePoints found at stereo calibration i would like to translate to a real world point with a X Y Z location of the checkboard. I tried to use rectify, disparty and reconstructScene but that didn't work. Problem their is disparty. Which should give a Z out but does not do the trick.

My goal is to solve the equation of:

P=projection matrix
T=translation vectors

(X_r,Y_r )= positie camera Right
(X_l,Y_l )= positie camera Left
X_(l→r)=X_l-P1[0][2]/W-T[0][0]/2
X_(r→l)=X_r-P2[0][2]/W-T[0][0]/2
ΔX=X_(r→l)=-X_(l→r)

delta X is the difference from X position calculated from left or right camera.