a simple 2d question

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  • Dominik Kaspar
    #1

    a simple 2d question

    Hello

    I want to catch mouse clicks on drawn lines and was dumbfound by the
    Line2D.intersec ts method.

    My code looks like this:
    Line2D.Double l = new Line2D.Double(0 , 0, 100, 100);
    if(l.intersects (49, 49, 51, 51)) System.out.prin tln("1");
    if(l.intersects (35, 35, 37, 37)) System.out.prin tln("2");

    The line (0,0)-(100,100) definitely doesn't intersect with the
    rectangle (35,35)-(37,37). But why the hell does the above code give
    the output "1" and "2"?!

    I hope somebody can eliminate my confusion.
    Dominik
    Tags: None
    • Dominik Kaspar
      #2
      Re: a simple 2d question

      Well, the last example were quite bad...
      How about the following one:

      Line2D.Double l = new Line2D.Double(1 20, 120, 240, 240);
      if(l.intersects (140, 190, 150, 200)) System.out.prin tln("1");

      Why does this result in the output "1"? The line l definitely doesn't
      intersects the square.

        Comment

        • Raymond DeCampo
          #3
          Re: a simple 2d question

          Dominik Kaspar wrote:[color=blue]
          > Well, the last example were quite bad...
          > How about the following one:
          >
          > Line2D.Double l = new Line2D.Double(1 20, 120, 240, 240);
          > if(l.intersects (140, 190, 150, 200)) System.out.prin tln("1");
          >
          > Why does this result in the output "1"? The line l definitely doesn't
          > intersects the square.[/color]

          Dominik,

          Are you reading the javadoc correctly? Note that Line2D.intersec t()
          expects the x-coord, y-coord, the width and the height of the rectangle
          (contrast with the Line2D.Double constructor). So the point (240,240)
          is inside your rectangle as:

          140 <= 240 <= 290 = 140+150 and
          190 <= 240 <= 390 = 190+200

          Ray

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