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Thread: Projecting a 3d point onto a plane

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    Default Projecting a 3d point onto a plane

    Hi
    i am working on information visualization, which use triangle projection to do it, that get n points from a higher dimensional space to a 2 dimensional space. i need to project points from an object and plot the n points in 2D. and i am going to use JAVA to write it.
    First, need to select a point to project and put it on the origin, and then put the 2nd point the right distance away from the 1st point.

    Second, calculate the 3rd point using the 1st and 2nd points, which form a triangle. For the remaining points, i need to pick 2 projected points and form a triangle with the remaining points.


    can anyone please help? i really don't know how to start it.
    Thank you


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    Super Moderator Norm's Avatar
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    Default Re: Java Programming

    It looks like you are looking for help with some math concepts and design vs for java programming help.
    If you are having problems coding your application in java, please ask your questions here.

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    Default Re: Java Programming

    yea, i dont know how to start doing this program....

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    Default Re: Java Programming

    Do you have the algorithm for the program?
    Given that, we can help you write the java program to implement that algorithm.

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    Default Re: Java Programming

    The algorithm is
    Pick a point and put it at the origin (0,0)
    Put the second point to the right distance away from the 1st point (0, distance(Point 1, Point 2))
    The 3rd point is the intersect of Point 1 and Point 2's circle which form a triangle with point 1 and point 2
    After projected 3 points
    For each remaining points
    we pick 2 projected points and form a triangle with remaining point

    i need a module that project 2 points and work out where is the 3rd point will go.

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    Super Moderator Norm's Avatar
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    Default Re: Java Programming

    Put the second point to the right distance away from the 1st point (0, distance(Point 1, Point 2))
    How is a point defined? x,y or ???
    How do you compute the "right distance"? How is this point defined?

    The 3rd point is the intersect of Point 1 and Point 2's circle which form a triangle with point 1 and point 2
    How do the circles (that implies 2 dimensions) intersect? Wouldn't there be two points where the circles intersect? What is the diameter of the circles?

    Where does the java programming come in for writing this program?

    Can you give an example: Two points and the third point.

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    Default Re: Java Programming

    Quote Originally Posted by mingming8888 View Post
    The 3rd point is the intersect of Point 1 and Point 2's circle which form a triangle with point 1 and point 2
    Unless you force some constraint on the triangle/Point3, in floating point space there are an infinite number of points which satisfy this criteria. If however point 3 is equidistant from 1 and 2, you are still left with 2 solutions.

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    Default Re: Java Programming

    Quote Originally Posted by copeg View Post
    Unless you force some constraint on the triangle/Point3, in floating point space there are an infinite number of points which satisfy this criteria. If however point 3 is equidistant from 1 and 2, you are still left with 2 solutions.
    Yea, the 3rd point is equidistant from 1 and 2, so the 2 solutions are a positive and negative y, is it? then i will take the positive one. But how can i do this?

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    Default Re: Java Programming

    Quote Originally Posted by Norm View Post
    How is a point defined? x,y or ???
    yes, x and y

    Quote Originally Posted by Norm View Post
    How do you compute the "right distance"? How is this point defined?
    after point 1 is projected, the right distance is the distance between point 1 and point 2 is the distance in the original space.

    Quote Originally Posted by Norm View Post
    Can you give an example: Two points and the third point.
    For example
    Point 1 is (0,0)
    Point 2 is (6,0)
    Point 3 is (3, 6)

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