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Replaced line intersection with something that does not cause infinite loops

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ZZYZX 2019-12-15 02:32:02 +02:00
parent 554ccc442f
commit d843a61d61
1 changed files with 73 additions and 60 deletions
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133
Source/Core/Geometry/Line2D.cs
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@ -226,70 +226,83 @@ namespace CodeImp.DoomBuilder.Geometry
return new Vector2D(v1.x + u * (v2.x - v1.x), v1.y + u * (v2.y - v1.y)); return new Vector2D(v1.x + u * (v2.x - v1.x), v1.y + u * (v2.y - v1.y));
} }
// Cohen-Sutherland algorithm private static bool IsEqualFloat(float a, float b)
public static Line2D ClipToRectangle(Line2D line, RectangleF rect, out bool intersects) {
return Math.Abs(a - b) < 0.0001f;
}
// Some random self-written aglrithm instead of Cohen-Sutherland algorithm which used to hang up randomly
public static Line2D ClipToRectangle(Line2D line, RectangleF rect, out bool intersects)
{ {
int flags1 = MapSet.GetCSFieldBits(line.v1, rect); float rateXY = 0f;
int flags2 = MapSet.GetCSFieldBits(line.v2, rect); if (line.v2.y != line.v1.y)
intersects = false; {
float dx = line.v2.x - line.v1.x;
float dy = line.v2.y - line.v1.y;
rateXY = dx / dy;
}
Line2D result = line; float x1 = line.v1.x, y1 = line.v1.y;
while (true) float x2 = line.v2.x, y2 = line.v2.y;
{
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; for (int i = 0; i < 2; i++)
int outFlags = flags1 != 0 ? flags1 : flags2; {
if ((outFlags & 0x1) > 0) // Top // check x1,y1
{ if (y1 < rect.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; x1 += (rect.Top - y1) * rateXY;
} y1 = rect.Top;
else if ((outFlags & 0x2) > 0) // Bottom }
{ if (x1 < rect.Left)
x = result.v1.x + (result.v2.x - result.v1.x) * (rect.Bottom - result.v1.y) / (result.v2.y - result.v1.y); {
y = rect.Bottom; if (rateXY != 0) y1 += (rect.Left - x1) / rateXY;
} x1 = rect.Left;
else if ((outFlags & 0x4) > 0) // Left }
{ // check x2,y2
y = result.v1.y + (result.v2.y - result.v1.y) * (rect.Left - result.v1.x) / (result.v2.x - result.v1.x); if (y2 < rect.Top)
x = rect.Left; {
} x2 += (rect.Top - y2) * rateXY;
else if ((outFlags & 0x8) > 0) // Right y2 = rect.Top;
{ }
y = result.v1.y + (result.v2.y - result.v1.y) * (rect.Right - result.v1.x) / (result.v2.x - result.v1.x); if (x2 < rect.Left)
x = rect.Right; {
} if (rateXY != 0) y2 += (rect.Left - x2) / rateXY;
else x2 = rect.Left;
{ }
intersects = true; // check x1,y1
return result; if (y1 > rect.Bottom)
} {
x1 -= (y1 - rect.Bottom) * rateXY;
y1 = rect.Bottom;
}
if (x1 > rect.Right)
{
if (rateXY != 0) y1 -= (x1 - rect.Right) / rateXY;
x1 = rect.Right;
}
// check x2,y2
if (y2 > rect.Bottom)
{
x2 -= (y2 - rect.Bottom) * rateXY;
y2 = rect.Bottom;
}
if (x2 > rect.Right)
{
if (rateXY != 0) y2 -= (x2 - rect.Right) / rateXY;
x2 = rect.Right;
}
}
if (outFlags == flags1) if ((IsEqualFloat(x1, x2) && (IsEqualFloat(x1, rect.Left) || IsEqualFloat(x1, rect.Right)) ||
{ (IsEqualFloat(y1, y2) && (IsEqualFloat(y1, rect.Bottom) || IsEqualFloat(y1, rect.Top)))))
result.v1 = new Vector2D(x, y); {
flags1 = MapSet.GetCSFieldBits(result.v1, rect); intersects = false;
} return new Line2D();
else }
{
result.v2 = new Vector2D(x, y); intersects = true;
flags2 = MapSet.GetCSFieldBits(result.v2, rect); return new Line2D(x1, y1, x2, y2);
} }
}
}
#endregion #endregion