Why do the Stereo Camera position not correspond with the "TranslationofCamera2" values ?

The calibrator app calibrates the stereo camera and output the extrinsic visualization as follows:

Which is very close to my real setup. As you can see from the image. The second camera translation can be approximated at [50 -11 -2]. Whereas the value that shows in my StereoParams object is "stereoParams.TranslationOfCamera2 = [-51.45 0.68 9.81]". Why is there the negative in X axis and other values? This does not make sense. Could anyone help me with this?

Answer 1

[Sharan Paramasivam Murugesan]

The values that you are comparing are of different context in meaning and does not correspond to each other. The values you see in the figure are the co-ordinates of the selected point in camera 2. Where as, TranslationOfCamera2 is the translation of camera 2 relative to camera 1 in world units. The negative X value denotes the translation of camera 2 to the right of camera 1 (from the viewer's perspective).

Refer to the following documentation for the same info:

https://www.mathworks.com/help/vision/ref/stereoparameters-class.html?s_tid=srchtitle

[Goku]

The values in the figure are also in world coordinates(mm). The first camera is in [0,0,0]. So should not the translation of the second camera be a 3-D vector and should be the same in the values and in the graph? (From my understanding from the link) I believe I should be able to plot both the camera positions(in mm) with the "stereoParams" object without using "ShowExtrinsics" and they should correspond with the "ShowExtrinsics" graph.

[Walter Roberson]

Mi C asks Sharan Paramasivam Murugesan :

which coordinate system is translationOfCamera2 defined?I think it should be defined in the camera1-based world coordinate system.