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Thread: is there a way to revolve an object around something in an elliptical pattern

  1. #1
    Junior Member Newbie
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    is there a way to revolve an object around something in an elliptical pattern

    is there a way to revolve an object around something in an elliptical pattern other than a circular pattern. If so, how

  2. #2
    Senior Member Regular Contributor
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    Re: is there a way to revolve an object around something in an elliptical pattern

    How are you revolving an object in circular pattern?
    It may help us to understand what u are trying to do.

  3. #3
    Junior Member Newbie
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    Re: is there a way to revolve an object around something in an elliptical pattern

    i am translating the object out and then rotating it. This is inside of a push,pop matrix

  4. #4
    Senior Member OpenGL Pro
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    Re: is there a way to revolve an object around something in an elliptical pattern

    Yes, you can. But only if you calculate a new translation. This is fairly easy if the ellipse's directrix is parallel to one of the coordinate axes, as then you just need to use the appropriate polar equation of a conic section (with the eccentricity set to produce an ellipse).

  5. #5
    Senior Member Regular Contributor
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    Re: is there a way to revolve an object around something in an elliptical pattern

    you could rotate it 't' radians and then translate it out 'r' units of length according to
    'r = sqrt[1 / (((cos(t)^2)/a^2) + ((sin(t)^2)/b^2)) ]'
    . Where 'a' is the x-axis axis and 'b' is the y-axis axis of the ellipse.

    This is the polar coordinate thing DFrey mentioned earlier. Be warned though that this method will cause the object to sweep out equal areas of the ellipse in equal time intervals. That means that the object seems to speed up when you go turn around the narrow curve of the ellipse.

    [This message has been edited by grady (edited 07-11-2001).]

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