From 3d point cloud to disparity map

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Hello,

I need to know if you got your coordinate system and translate the output of ReprojectImageTo3D function as I am working in the same topic, I have like this result

X coordinate values always between 350 - 450 Y coordinate values always between -80 to -30 z coordinates values always between 230 - 280 and sometimes 10000 when so far

Thank you for your help

Hi AgentCain,

I don't know if there is a function that implements this for you, but going back from 3D PointCloud to disparity is relatively easy knowing the reprojection matrix Q (one of the arguments to the function reprojectImageTo3D).

The matrix Q has the following structure:

Q =| 1 0 0 -Cx |
   | 0 1 0 -Cy |
   | 0 0 0  f  |
   | 0 0 a  b  |

So assuming that your 3D point has the coordinates (X', Y', Z'), the disparity (d) and its position on the disparity image (Ix and Iy) can be calculated as follow:

d = (f - Z' * b ) / ( Z' * a)

Ix = X' * ( d * a + b ) + Cx

Iy = Y' * ( d * a + b ) + Cy

I attach a picture of the math, just in case you want to know the details. I hope this helps.

I think you can calculate distance between point cloud and it projection to plane, multiply by proper factor and obtain your disparity point.