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-   -   2D rotations about the center of mass (https://www.askmehelpdesk.com/showthread.php?t=18869)

  • Jan 26, 2006, 03:02 PM
    janguera
    2D rotations about the center of mass
    Hey all,

    I've place this post on the Math site, but I'm hoping that I might get an answer from someone here sooner!


    I'm trying to figure out how to calculate the resultant polar coordinates of a triangle following the triangle's 45 degree rotation about it's own center of mass. I've seen how to rotate the triangle about the center of the screen using:

    In 2D, you make (X,Y) from (x,y) with a rotation by angle t so:
    X = x cos t - y sin t
    Y = x sin t + y cos t

    ... but this only rotates the triangle with regards to the background. I want to figure out a way to find the NEW polar coordinates of the triangle after a 45 degree rotation. Any and all suggestions/comments are welcome!

    Joaquin :)
  • Mar 21, 2006, 07:53 PM
    dmatos
    Why not translate the triangle so the centre of mass is at the origin, then rotate it, then translate it back?

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