public static Line2D ParseLine(string lineText)
{
string[] splitLine = lineText.Split(' ');
Line2D line = new Line2D();
try
{
line.Start = new Vector3<double>(double.Parse(splitLine[0]), double.Parse(splitLine[1]), 1);
line.End = new Vector3<double>(double.Parse(splitLine[2]), double.Parse(splitLine[3]), 1);
}
catch (FormatException ex)
{
Console.WriteLine("ERROR: Line in incorrect format!");
Console.WriteLine(ex.ToString());
}
return line;
}
// Using the cohen sutherland algorithm
private Line2D ClipLine(Line2D line)
{
Line2D newLine = new Line2D();
newLine.Start = new Vector3<double>(line.Start[0], line.Start[1], 1);
newLine.End = new Vector3<double>(line.End[0], line.End[1], 1);
BitCodes code1 = GetCode(newLine.Start);
BitCodes code2 = GetCode(newLine.End);
while (true)
{
if ((code1 | code2) == BitCodes.Middle)
{
//Hooray we don't need to clip!
return newLine;
}
else if ((code1 & code2) != BitCodes.Middle)
{
//Line2D totally outside area
return null;
}
else
{
//More complicated...
//at least one endpoint is outside
//Need to check for flipped bits
//can use xor
byte temp = (byte)(code1 ^ code2);
byte bitNumber = 4;
//If the codes are not either of the trivial cases, at least one bit must be flipped.
//Therefore this loop cannot go infinite
while (temp != 1)
{
temp = (byte)(temp >> 1);
bitNumber--;
}
//Pick which point to work on
double x = 0;
double y = 0;
BitCodes workingCode = code1;
switch (bitNumber)
{
case 1:
if ((code2 & BitCodes.Top) != 0)
workingCode = code2;
// y0 > WT and y1 <= WT
// yc = WT
// xc = ((WT - y0)/(y1 - y0))*(x1 - x0) + x0
x = ((m_yMax - newLine.Start[1]) / (newLine.End[1] - newLine.Start[1])) * (newLine.End[0] - newLine.Start[0]) + newLine.Start[0];
y = m_yMax;
break;
case 2:
if ((code2 & BitCodes.Bottom) != 0)
workingCode = code2;
// y0 < WB and y1 >= WB
// yc = WB
// xc = ((WB - y0)/(y1 - y0))*(x1 - x0) + x0
x = ((m_yMin - newLine.Start[1]) / (newLine.End[1] - newLine.Start[1])) * (newLine.End[0] - newLine.Start[0]) + newLine.Start[0];
y = m_yMin;
break;
case 3:
if ((code2 & BitCodes.Right) != 0)
workingCode = code2;
// x0 > WR and x2 <= WR
// xc = WR
// yc = ((WR - x0)/(x1 - x0))*(y1 - y0) + y0
y = ((m_xMax - newLine.Start[0]) / (newLine.End[0] - newLine.Start[0])) * (newLine.End[1] - newLine.Start[1]) + newLine.Start[1];
x = m_xMax;
break;
case 4:
if ((code2 & BitCodes.Left) != 0)
workingCode = code2;
// x0 < WL and x1 >= WL
// xc = WL
// yc = ((WL - x0)/(x1 - x0))*(y1 - y0) + y0
y = ((m_xMin - newLine.Start[0]) / (newLine.End[0] - newLine.Start[0])) * (newLine.End[1] - newLine.Start[1]) + newLine.Start[1];
x = m_xMin;
break;
}
if (code1 == workingCode)
{
newLine.Start[0] = x;
newLine.Start[1] = y;
code1 = GetCode(newLine.Start);
}
else
{
newLine.End[0] = x;
newLine.End[1] = y;
code2 = GetCode(newLine.End);
}
}
}
}
//Functions that are commented "Based on textbook algorithm" were inspired by ntroduction to Computer Graphics(Foley, Van Dam, et al)
//All these functions rely on the polygon being specified in counterclockwise vertex ordering.
//Based on textbook algorithm
// Calculates the intersection of the line formed by two vertices and a line.
private Vector3<double> Intersect(Vector3<double> begin, Vector3<double> end, Line2D clipEdge)
{
Vector3<double> ret = new Vector3<double>();
if (clipEdge.Start.Y == clipEdge.End.Y)
{
ret.X = begin.X + (clipEdge.Start.Y - begin.Y) * (end.X - begin.X) / (end.Y - begin.Y);
ret.Y = clipEdge.Start.Y;
}
else
{
ret.X = clipEdge.Start.X;
ret.Y = begin.Y + (clipEdge.Start.X - begin.X) * (end.Y - begin.Y) / (end.X - begin.X);
}
return ret;
}
//Based on textbook algorithm
//Implements the sutherlandHodgman polygon clipping algorithm. This function will only
//clip the polygon against one clip edge at a time. Therefore, to clip the entire polygon, we feed the output
//of this command into the input of another call to this with a different clip edge and keep
// doing this until we run out of clip edges
private List<Vector3<double>> SutherlandHodgman(List<Vector3<double>> inVertices, Line2D clipEdge)
{
List<Vector3<double>> output = new List<Vector3<double>>();
Vector3<double> s = inVertices.Last();
Vector3<double> p;
for(int i = 0; i < inVertices.Count; i++)
{
p = inVertices[i];
if (Inside(p, clipEdge))
{
if (Inside(s, clipEdge))
{
output.Add(p);
}
else
{
output.Add(Intersect(s, p, clipEdge));
output.Add(p);
}
}
else if(Inside(s, clipEdge))
{
output.Add(Intersect(s, p, clipEdge));
}
s = p;
}
return output;
}
//Based on textbook algorithm
//Determines if a point is inside a given line (inside defined as being to the left of the clipEdge while oriented in the direction of the clip edge)
private bool Inside(Vector3<double> test, Line2D clipEdge)
{
if (clipEdge.End.X > clipEdge.Start.X)
if (test.Y >= clipEdge.Start.Y)
return true;
if (clipEdge.End.X < clipEdge.Start.X)
if (test.Y <= clipEdge.Start.Y)
return true;
if (clipEdge.End.Y > clipEdge.Start.Y)
if (test.X <= clipEdge.End.X)
return true;
if (clipEdge.End.Y < clipEdge.Start.Y)
if (test.X >= clipEdge.End.X)
return true;
return false;
}
