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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));
}
// Cohen-Sutherland algorithm
public static Line2D ClipToRectangle(Line2D line, RectangleF rect, out bool intersects)
private static bool IsEqualFloat(float a, float b)
{
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);
int flags2 = MapSet.GetCSFieldBits(line.v2, rect);
intersects = false;
float rateXY = 0f;
if (line.v2.y != line.v1.y)
{
float dx = line.v2.x - line.v1.x;
float dy = line.v2.y - line.v1.y;
rateXY = dx / dy;
}
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 x1 = line.v1.x, y1 = line.v1.y;
float x2 = line.v2.x, y2 = line.v2.y;
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;
}
for (int i = 0; i < 2; i++)
{
// check x1,y1
if (y1 < rect.Top)
{
x1 += (rect.Top - y1) * rateXY;
y1 = rect.Top;
}
if (x1 < rect.Left)
{
if (rateXY != 0) y1 += (rect.Left - x1) / rateXY;
x1 = rect.Left;
}
// check x2,y2
if (y2 < rect.Top)
{
x2 += (rect.Top - y2) * rateXY;
y2 = rect.Top;
}
if (x2 < rect.Left)
{
if (rateXY != 0) y2 += (rect.Left - x2) / rateXY;
x2 = rect.Left;
}
// check x1,y1
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)
{
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);
}
}
}
if ((IsEqualFloat(x1, x2) && (IsEqualFloat(x1, rect.Left) || IsEqualFloat(x1, rect.Right)) ||
(IsEqualFloat(y1, y2) && (IsEqualFloat(y1, rect.Bottom) || IsEqualFloat(y1, rect.Top)))))
{
intersects = false;
return new Line2D();
}
intersects = true;
return new Line2D(x1, y1, x2, y2);
}
#endregion