SuperStrict

Graphics 640, 480


Local points:Double[3,2]
Local state:Int
Local circle:Double[] = [0:Double, 0:Double, 0:Double]

While Not KeyHit(KEY_ESCAPE)

   Cls

   If MouseHit(1) Then
      points[state,0] = MouseX()
      points[state,1] = MouseY()
      state :+ 1
      If state = 3 Then state = 0

      circle = CalcCircle(points[0,0], points[0,1], points[1,0], points[1,1], points[2,0], points[2,1])
   End If

   SetColor 255, 255, 255
   DrawOval circle[0]-circle[2], circle[1]-circle[2], circle[2]*2, circle[2]*2
   SetColor 0, 0, 255
   DrawText "x: " + circle[0] + " y: " + circle[1] + " r: " + circle[2], 0, 0
   For Local i:Int = 0 Until 3
      DrawOval points[i,0]-5, points[i,1]-5, 10, 10
   Next

   Flip

Wend


Flip
WaitKey()



Function CalcCircle:Double[](a:Double, b:Double, c:Double, d:Double, e:Double, f:Double)

   Local x:Double, y:Double, r:Double

   ' (a - x)^2 + (b - y)^2 = r^2
   ' (c - x)^2 + (d - y)^2 = r^2
   ' (e - x)^2 + (f - y)^2 = r^2

   ' gleichsetzen:
   '  => (a - x)^2 + (b - y)^2 = (c - x)^2 + (d - y)^2
   ' <=> y' = (a^2 - 2*a*x + b^2 - c^2 + 2*c*x - d^2) / (2*b - 2*d)
   '
   '  => (c - x)^2 + (d - y)^2 = (e - x)^2 + (f - y)^2
   ' <=> y'' = (c^2 - 2*c*x + d^2 - f^2 + 2*e*x - e^2) / (2*d - 2*f)
   '
   ' y' = y''
   ' <=> (a^2 - 2*a*x + b^2 - c^2 + 2*c*x - d^2) / (2*b - 2*d) = (c^2 - 2*c*x + d^2 - f^2 + 2*e*x - e^2) / (2*d - 2*f)
   ' <=> x = ((-a^2 - b^2 + c^2 + d^2) / (2*b - 2*d) + (c^2 + d^2 - e^2 - f^2) / (2*d - 2*f)) / ((-2*a + 2*c) / (2*b - 2*d) + (2*c - 2*e) / (2*d - 2*f))

   x = ((-(a^2) - b^2 + c^2 + d^2) / (2*b - 2*d) + (c^2 + d^2 - e^2 - f^2) / (2*d - 2*f)) / ((-2*a + 2*c) / (2*b - 2*d) + (2*c - 2*e) / (2*d - 2*f))

   y = (a^2 - 2*a*x + b^2 - c^2 + 2*c*x - d^2) / (2*b - 2*d)

   r = Sqr((a - x)*(a - x) + (b - y)*(b - y))

   Return [x, y, r]

End Function