Intrinsic and Extrinsic Camera Properties

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goktug
Posts: 4
Joined: Mon Oct 21, 2019 1:41 pm

Intrinsic and Extrinsic Camera Properties

Post by goktug »

I need to use calibration matrices of pybullet camera (intrinsic and extrinsic camera matrices) in my project. However, I could not find them. As far as I know, pybullet only provides view matrix and projection matrix of the camera. According to my research, pybullet benefits from OpenGL.

I have checked and examined OpenGL documentation to construct intrinsic and extrinsic matrices from projection and view matrix. However, I could not find a clear conversion. What I have found up to now is two of three components in intrinsic matrix in pybullet by making extensive amount of calculation and research:

Intrinsic Components:
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* Focal length values (fx, fy)
* Two principal point values (cx, cy)
* Pixel Skew (s)

What I found:
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* Focal Length: Since there is only one camera eye, there is only one focal length, which is equal to 1 / tan(q/2) in which q refers to the angle "field of view" in computeProjectionMatrixFOV function.

* Principal Values: The principal points are indices of middle pixel in the image, which is 250 for 500x500 image.

However, In spite of my 2 days research, I could not find pixel skew value. Is there anyone who can provide pixel skew and extrinsic matrix of pybullet camera image ? I think that we need these matrices for many computer vision purposes.
zachjiang
Posts: 1
Joined: Thu Jun 17, 2021 3:09 pm

Re: Intrinsic and Extrinsic Camera Properties

Post by zachjiang »

Check out this post in stackoverflow:
https://stackoverflow.com/questions/604 ... 0#60450420

The skew is 0
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