Jarvis algorithm (gift-wrapping) or graham-scan - C#
I have a list of Shapes and I have to make a convex hull around them. I tried to do a gift-wrapping algorithm (Jarvis). So far I have foud a plenty of pseudocodes and I understand the logic, but I can't program it. Could only do the 1st step - finding the lowest & "leftest" shape.
List<Point> Ob = new List<Point>();
Point p = new Point();
for (int i = 0; i < L.Count - 1; i++)
{
if (L[i].CoordinateX < L[i + 1].CoordinateX) p.X = (int)L[i].CoordinateX;
if (L[i].CoordinateY < L[i + 1].CoordinateY) p.Y = (int)L[i].CoordinateY;
}
Ob.Add(p);
So then I tried to find the smallest angle. My logic was that the smaller angle the smaller the cos of this angle
double angle = 0, angle1 = 0;
int num = 0;
for (int k = 0; k < L.Count - 1; k++)
{
angle = Math.Cos((Math.Sqrt(Math.Pow((L[k].CoordinateX - p.X), 2) + Math.Pow((p.Y - L[k].CoordinateY), 2))) / (Math.Sqrt(Math.Pow((L[k].CoordinateX - p.X), 2) + Math.Pow((L[k].CoordinateY - p.Y), 2))));
angle1 = Math.Cos((Math.Sqrt(Math.Pow((L[k + 1].CoordinateX - p.X), 2) + Math.Pow((p.Y - L[k + 1].CoordinateY), 2))) / (Math.Sqrt(Math.Pow((L[k + 1].CoordinateX - p.X), 2) + Math.Pow((L[k + 1].CoordinateY - p.Y), 2))));
if (angle < angle1) num = k;
}
Point p1 = new Point((int)L[num].CoordinateX, (int)L[num].CoordinateY);
e.Graphics.DrawLine(new Pen(Color.Black), p, p1);
But this code ended in this added 3 circles first, then added 1 more and so on. Obviously this doesn't make any sense.
And this
Do you know any realizations of Graham or Jarvis to look at?
c# algorithm graphics grahams-scan
asked Nov 12 '18 at 16:47
Moth Lamp
112
add a comment |
I have a list of Shapes and I have to make a convex hull around them. I tried to do a gift-wrapping algorithm (Jarvis). So far I have foud a plenty of pseudocodes and I understand the logic, but I can't program it. Could only do the 1st step - finding the lowest & "leftest" shape.
List<Point> Ob = new List<Point>();
Point p = new Point();
for (int i = 0; i < L.Count - 1; i++)
{
if (L[i].CoordinateX < L[i + 1].CoordinateX) p.X = (int)L[i].CoordinateX;
if (L[i].CoordinateY < L[i + 1].CoordinateY) p.Y = (int)L[i].CoordinateY;
}
Ob.Add(p);
So then I tried to find the smallest angle. My logic was that the smaller angle the smaller the cos of this angle
double angle = 0, angle1 = 0;
int num = 0;
for (int k = 0; k < L.Count - 1; k++)
{
angle = Math.Cos((Math.Sqrt(Math.Pow((L[k].CoordinateX - p.X), 2) + Math.Pow((p.Y - L[k].CoordinateY), 2))) / (Math.Sqrt(Math.Pow((L[k].CoordinateX - p.X), 2) + Math.Pow((L[k].CoordinateY - p.Y), 2))));
angle1 = Math.Cos((Math.Sqrt(Math.Pow((L[k + 1].CoordinateX - p.X), 2) + Math.Pow((p.Y - L[k + 1].CoordinateY), 2))) / (Math.Sqrt(Math.Pow((L[k + 1].CoordinateX - p.X), 2) + Math.Pow((L[k + 1].CoordinateY - p.Y), 2))));
if (angle < angle1) num = k;
}
Point p1 = new Point((int)L[num].CoordinateX, (int)L[num].CoordinateY);
e.Graphics.DrawLine(new Pen(Color.Black), p, p1);
But this code ended in this added 3 circles first, then added 1 more and so on. Obviously this doesn't make any sense.
And this
Do you know any realizations of Graham or Jarvis to look at?
c# algorithm graphics grahams-scan
asked Nov 12 '18 at 16:47
Moth Lamp
112
You can check this example of Graham scan: github.com/MathBunny/convex-hull-visualizer/blob/master/app/src/…
– MathBunny
Nov 12 '18 at 23:34
add a comment |
I have a list of Shapes and I have to make a convex hull around them. I tried to do a gift-wrapping algorithm (Jarvis). So far I have foud a plenty of pseudocodes and I understand the logic, but I can't program it. Could only do the 1st step - finding the lowest & "leftest" shape.
List<Point> Ob = new List<Point>();
Point p = new Point();
for (int i = 0; i < L.Count - 1; i++)
{
if (L[i].CoordinateX < L[i + 1].CoordinateX) p.X = (int)L[i].CoordinateX;
if (L[i].CoordinateY < L[i + 1].CoordinateY) p.Y = (int)L[i].CoordinateY;
}
Ob.Add(p);
So then I tried to find the smallest angle. My logic was that the smaller angle the smaller the cos of this angle
double angle = 0, angle1 = 0;
int num = 0;
for (int k = 0; k < L.Count - 1; k++)
{
angle = Math.Cos((Math.Sqrt(Math.Pow((L[k].CoordinateX - p.X), 2) + Math.Pow((p.Y - L[k].CoordinateY), 2))) / (Math.Sqrt(Math.Pow((L[k].CoordinateX - p.X), 2) + Math.Pow((L[k].CoordinateY - p.Y), 2))));
angle1 = Math.Cos((Math.Sqrt(Math.Pow((L[k + 1].CoordinateX - p.X), 2) + Math.Pow((p.Y - L[k + 1].CoordinateY), 2))) / (Math.Sqrt(Math.Pow((L[k + 1].CoordinateX - p.X), 2) + Math.Pow((L[k + 1].CoordinateY - p.Y), 2))));
if (angle < angle1) num = k;
}
Point p1 = new Point((int)L[num].CoordinateX, (int)L[num].CoordinateY);
e.Graphics.DrawLine(new Pen(Color.Black), p, p1);
But this code ended in this added 3 circles first, then added 1 more and so on. Obviously this doesn't make any sense.
And this
Do you know any realizations of Graham or Jarvis to look at?
c# algorithm graphics grahams-scan
asked Nov 12 '18 at 16:47
Moth Lamp
112
I have a list of Shapes and I have to make a convex hull around them. I tried to do a gift-wrapping algorithm (Jarvis). So far I have foud a plenty of pseudocodes and I understand the logic, but I can't program it. Could only do the 1st step - finding the lowest & "leftest" shape.
List<Point> Ob = new List<Point>();
Point p = new Point();
for (int i = 0; i < L.Count - 1; i++)
{
if (L[i].CoordinateX < L[i + 1].CoordinateX) p.X = (int)L[i].CoordinateX;
if (L[i].CoordinateY < L[i + 1].CoordinateY) p.Y = (int)L[i].CoordinateY;
}
Ob.Add(p);
So then I tried to find the smallest angle. My logic was that the smaller angle the smaller the cos of this angle
double angle = 0, angle1 = 0;
int num = 0;
for (int k = 0; k < L.Count - 1; k++)
{
angle = Math.Cos((Math.Sqrt(Math.Pow((L[k].CoordinateX - p.X), 2) + Math.Pow((p.Y - L[k].CoordinateY), 2))) / (Math.Sqrt(Math.Pow((L[k].CoordinateX - p.X), 2) + Math.Pow((L[k].CoordinateY - p.Y), 2))));
angle1 = Math.Cos((Math.Sqrt(Math.Pow((L[k + 1].CoordinateX - p.X), 2) + Math.Pow((p.Y - L[k + 1].CoordinateY), 2))) / (Math.Sqrt(Math.Pow((L[k + 1].CoordinateX - p.X), 2) + Math.Pow((L[k + 1].CoordinateY - p.Y), 2))));
if (angle < angle1) num = k;
}
Point p1 = new Point((int)L[num].CoordinateX, (int)L[num].CoordinateY);
e.Graphics.DrawLine(new Pen(Color.Black), p, p1);
But this code ended in this added 3 circles first, then added 1 more and so on. Obviously this doesn't make any sense.
And this
Do you know any realizations of Graham or Jarvis to look at?
c# algorithm graphics grahams-scan
c# algorithm graphics grahams-scan
asked Nov 12 '18 at 16:47
Moth Lamp
112
asked Nov 12 '18 at 16:47
Moth Lamp
112
edited Nov 12 '18 at 18:04
asked Nov 12 '18 at 16:47
Moth Lamp
112
asked Nov 12 '18 at 16:47
Moth Lamp
112
asked Nov 12 '18 at 16:47
Moth Lamp
112
112
You can check this example of Graham scan: github.com/MathBunny/convex-hull-visualizer/blob/master/app/src/…
– MathBunny
Nov 12 '18 at 23:34
add a comment |
You can check this example of Graham scan: github.com/MathBunny/convex-hull-visualizer/blob/master/app/src/…
– MathBunny
Nov 12 '18 at 23:34
You can check this example of Graham scan: github.com/MathBunny/convex-hull-visualizer/blob/master/app/src/…
– MathBunny
Nov 12 '18 at 23:34
You can check this example of Graham scan: github.com/MathBunny/convex-hull-visualizer/blob/master/app/src/…
– MathBunny
Nov 12 '18 at 23:34
add a comment |
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You can check this example of Graham scan: github.com/MathBunny/convex-hull-visualizer/blob/master/app/src/…
– MathBunny
Nov 12 '18 at 23:34