Write a routine to draw a circle ?

Question

Hi guys, What a routine to draw a circle (x ** 2 + y ** 2 = r ** 2) without making use of any floating point computations at all. Thanks

Vulpes · Answer

Oops, forgot to generate the points for negative values of y. Here's the revised code - points generated in clockwise order: using System; struct Point { public int X, Y; public Point(int x, int y) { X = x; Y = y; } public override string ToString() { return String.Format("({0}, {1})", X, Y); } } class Circle { static void Main() { Console.Write ("Enter radius : "); int r; int.TryParse(Console.ReadLine(), out r); if (r { Console.WriteLine("Radius must be > 0"); return; } /* assuming center of circle is at origin (0,0) generate points (x, y) to draw circle */ Point[] points = new Point[4 * r]; int y; for(int x = - r; x { y = Sqrt(r * r - x * x); points[x + r] = new Point(x, y); } // the y values will be symmetric for x == 1 to x == r for(int x = 1; x { y = points[r - x].Y; points[x + r] = new Point(x, y); } // the points for negative values of y will be symmetric with those for postive values for (int x = r - 1; x >= - r + 1; x--) { y = - points[r + x].Y; points[3 * r - x] = new Point(x, y); } // print results Console.Clear(); foreach(Point p in points) Console.WriteLine(p); Console.ReadKey(); } static int Sqrt(int ys) { int t2 = 0; while (t2 * t2 if (ys == t2 * t2) return t2; int t1 = t2 - 1; int d2 = t2 * t2 - ys; int d1 = ys - t1 * t1; if (d2 return t1; } }

Vulpes · Answer

Here's a possible way to generate the points to draw a circle of a given radius, with center at the origin using only integer arithmetic. Of course, for a given x value, we can only express y to the nearer integer unless r^2 - x^2 is an exact square. using System; struct Point { public int X, Y; public Point(int x, int y) { X = x; Y = y; } public override string ToString() { return String.Format("({0},{1})", X, Y); } } class Circle { static void Main() { Console.Write ("Enter radius : "); int r; int.TryParse(Console.ReadLine(), out r); if (r { Console.WriteLine("Radius must be > 0"); return; } /* assuming center of circle is at origin (0,0) generate points (x, y) to draw circle */ Point[] points = new Point[2 * r + 1]; int y; for(int x = - r; x { y = Sqrt(r * r - x * x); points[x + r] = new Point(x, y); } // the y values will be symmetric for x == 1 to x == r for(int x = 1; x { y = points[r - x].Y; points[x + r] = new Point(x, y); } // print results Console.Clear(); foreach(Point p in points) Console.WriteLine(p); Console.ReadKey(); } static int Sqrt(int ys) { int t2 = 0; while (t2 * t2 if (ys == t2 * t2) return t2; int t1 = t2 - 1; int d2 = t2 * t2 - ys; int d1 = ys - t1 * t1; if (d2 return t1; } }

Write a routine to draw a circle ?

Answers (2)