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Thread: How does this animation work?

  1. #1
    Super Member maxpancho's Avatar
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    How does this animation work?

    I'm guessing there's some kind of system of equations (matrix?) that calculates coordinates for all the points such that they simultaneously represent the figure spinning both ways? Not looking for technical details, though, just an outline/intuition. I know computer animation/graphics use linear algebra, right? So is it the main prerequisite for understanding/creating stuff like this?

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  2. #2
    MHF Contributor
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    Re: How does this animation work?

    given a point in space it's simple enough to rotate that point along some chosen axis.

    There are mathematical objects called rotation matrices that when applied by multiplication to a vector of position coordinates will perform this rotation.

    So, in this case, take the set of points that represent your 3D object, and every time step rotate each one by some amount. Erase the old point and draw the new one.

    repeat forever.

    If your 3D object consists of points connected by lines you would rotate each point, erase the old line, and just draw a new line between the rotated points using the standard algorithm to do that.

    You wouldn't bother trying to rotate every point on the line, just the endoints.
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  3. #3
    Super Member maxpancho's Avatar
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    Re: How does this animation work?

    Quote Originally Posted by romsek View Post
    given a point in space it's simple enough to rotate that point along some chosen axis.

    There are mathematical objects called rotation matrices that when applied by multiplication to a vector of position coordinates will perform this rotation.

    So, in this case, take the set of points that represent your 3D object, and every time step rotate each one by some amount. Erase the old point and draw the new one.

    repeat forever.

    If your 3D object consists of points connected by lines you would rotate each point, erase the old line, and just draw a new line between the rotated points using the standard algorithm to do that.

    You wouldn't bother trying to rotate every point on the line, just the endoints.
    Thanks. However, I'm not sure if you noticed or not, but you can view the object as both rotating clockwise and counterclockwise .
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    Re: How does this animation work?

    Quote Originally Posted by maxpancho View Post
    Thanks. However, I'm not sure if you noticed or not, but you can view the object as both rotating clockwise and counterclockwise .
    Without taking the time to study this I'm going to go with that being an optical illusion.

    Our eyes sample at a finite rate and aliasing can occur. This would result in objects appearing to rotate backwards.

    I'm sure you can find more info on this with a few googles.
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    Re: How does this animation work?

    Quote Originally Posted by maxpancho View Post
    Thanks. However, I'm not sure if you noticed or not, but you can view the object as both rotating clockwise and counterclockwise .
    Yes, but as romsek suggested. that is an optical illusion and has nothing to do with how it is actually rotating nor with how the picture was created.
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    Super Member maxpancho's Avatar
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    Re: How does this animation work?

    Quote Originally Posted by HallsofIvy View Post
    Yes, but as romsek suggested. that is an optical illusion and has nothing to do with how it is actually rotating nor with how the picture was created.
    Okay. I wasn't sure if any 3D object (say, figure) plotted like that would appear to rotate both ways, so I thought maybe it was some kind of optimization problem.
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