// Cohen-Sutherland algorithm
public static Line2D ClipToRectangle(Line2D line, RectangleF rect, out bool intersects)
{
int flags1 = MapSet.GetCSFieldBits(line.v1, rect);
int flags2 = MapSet.GetCSFieldBits(line.v2, rect);
intersects = false;
Line2D result = line;
while (true)
{
if (flags1 == 0 && flags2 == 0)
{
// Line is fully inside the box
intersects = true;
return(result);
}
if ((flags1 & flags2) != 0)
{
// Both points are in the same outer area
intersects = false;
return(new Line2D());
}
float x, y;
int outFlags = flags1 != 0 ? flags1 : flags2;
if ((outFlags & 0x1) > 0) // Top
{
x = result.v1.x + (result.v2.x - result.v1.x) * (rect.Top - result.v1.y) / (result.v2.y - result.v1.y);
y = rect.Top;
}
else if ((outFlags & 0x2) > 0) // Bottom
{
x = result.v1.x + (result.v2.x - result.v1.x) * (rect.Bottom - result.v1.y) / (result.v2.y - result.v1.y);
y = rect.Bottom;
}
else if ((outFlags & 0x4) > 0) // Left
{
y = result.v1.y + (result.v2.y - result.v1.y) * (rect.Left - result.v1.x) / (result.v2.x - result.v1.x);
x = rect.Left;
}
else if ((outFlags & 0x8) > 0) // Right
{
y = result.v1.y + (result.v2.y - result.v1.y) * (rect.Right - result.v1.x) / (result.v2.x - result.v1.x);
x = rect.Right;
}
else
{
intersects = true;
return(result);
}
if (outFlags == flags1)
{
result.v1 = new Vector2D(x, y);
flags1 = MapSet.GetCSFieldBits(result.v1, rect);
}
else
{
result.v2 = new Vector2D(x, y);
flags2 = MapSet.GetCSFieldBits(result.v2, rect);
}
}
}
