CODEWITHSUNDEEP
computer-visioncamera-calibrationstereo-3drotational-matricesprojection-matrix
volperossa
volperossa

Reputation: 1431

Camera projection matrix: why transpose rotation matrix?

In the following:

http://cvlab.epfl.ch/files/content/sites/cvlab2/files/data/strechamvs/rathaus.tar.gz

there's a README file that says:

a 3D point X will be projected into the images in the usual way:
x = K[R^T|-R^T t]X

I remember that 3D to 2D Camera Projection Matrix requires the R rotation, not the transpose R matrix, i.e. I expect:

 x = K[R|-R t]X

Why does it say R^T and not simply R ?

Upvotes: 2

Views: 1714

Answers (2)

DrPepperJo
DrPepperJo

Reputation: 722

Since R^T == R^{-1}, it seems like the upper formula just expects the rotation to be available in the reverse direction of the below one. Just make sure to use the direction they expect as input.

Upvotes: 2

Unapiedra
Unapiedra

Reputation: 16197

It depends in which direction R was determined. I.e. is it a transformation of the camera in the global reference frame, or is it a transformation of the points in the local camera's reference frame.

The true answer is: Don't worry just check that what you've got is right.

Upvotes: 3

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