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How to convert 3D point cloud (extracted from sparse 3D reconstruction) from pixels to millmeters?

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kijo maken
kijo maken on 15 Aug 2014
Commented: Luca on 29 Oct 2014
I have found a 3D point cloud using 3D sparse reconstruction (like this example http://www.mathworks.com/help/vision/ug/sparse-3-d-reconstruction-from-multiple-views.html )
Now I was wondering how I can convert the (X,Y,Z) in this point cloud to actual real world measurements in millimeters.

Answers (1)

Dima Lisin
Dima Lisin on 25 Aug 2014
Hi Kijo,
In this example the (X, Y, Z) world coordinates are already in millimeters.
  7 Comments
Luca
Luca on 29 Oct 2014
Hi Dima, Thanks for the step by step guide. So I followed that and I am happy with the results.
The only problem I have is that the Z values in point cloud are negative!
Might that be coming from the fact that I am using a different checkerboard pattern? because I am getting this warning: " Warning: The checkerboard must be asymmetric: one side should be even, and the other should be odd. Otherwise, the orientation of the board may be detected incorrectly ." I am using Bouguet's pattern in his Caltech's toolbox.
Also I realized if I change the order of images when reading and extracting features, then I will have positive Z values in point cloud, but the results are way off and don't match with the scene! if I read right images first and then left images when I stereo calibrate the cameras, then I have to read them the same order when extracting features, right?

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