Camera Projection Matrix

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  • Yingliang
    Blossoming 3Dflower
    • Dec 2015
    • 2

    Camera Projection Matrix

    Hello, I have three questions.
    1. I'm trying to export camera locations but I don't know how.
    2. And I try to export camera projection matrix, I get a .ppm file in which there is a 4 * 4 matrix, I support the projection matrix is 3*4, why is 4 * 4 in the ppm file?
    3. I also export the external paras, and I get six numbers for each image, does these six numbers represent for 3 * 1 rotation vector
    and 3 * 1 translation vector?

    Thank you very much!
  • Andrea Alessi
    3Dflow Staff
    • Oct 2013
    • 1304

    #2
    Hello,

    1. what do you mean by locations? If you're referring to the X,Y,Z position (the same one you see when right clicking a camera and selecting properties) you can do so by exporting their external parameters (or if you meant when exporting a mesh, you can do so by using the fbx file format)

    2. The ppm file is composed by two parts:
    the first part is a 3x4 matrix (ppm)
    the second part (the last line) file is the camera calibration radial distortion (5 values, it's not a 4x4 matrix)

    ppm is composed as A * rt , where rt is composed as [R T] and R is 3x3 rotation matrix and T is a 3x1 displacement vector

    (also remember that you can export matrices for opengl in the same export dialog)

    3. externals are exported as ImageName x y z a1 a2 a3 , so: image name, x y z position and first axis of rotation X, second axis of Rotation y, third axis of rotation Z

    Andrea

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    • Yingliang
      Blossoming 3Dflower
      • Dec 2015
      • 2

      #3
      Thank you very much, Andrea! You really help me a lot.

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