线与线相交、线与矩形相交判断

///
/// 只要线与矩形有一条线有相交，则线与矩形相交
///
public class LineWithRect : MonoBehaviour
{
public Rect rect = new Rect(0, 0, 100, 100);
public Transform LineStart;
public Transform lineEnd;

Vector3 VecLineStart;
Vector3 vecLineEnd;
Vector3 leftDown
{
get
{
return new Vector2(rect.xMin, rect.yMin);
}
}
Vector3 leftUp
{
get
{
return new Vector2(rect.xMin, rect.yMax);
}
}
Vector3 RigtDown
{
get
{
return new Vector2(rect.xMax, rect.yMin);
}
}
Vector3 RightUp
{
get
{
return new Vector2(rect.xMax, rect.yMax);
}
}
private void OnDrawGizmos()
{
if (LineStart == null || lineEnd == null)
return;
VecLineStart = new Vector2(LineStart.position.x, LineStart.position.y);
vecLineEnd = new Vector2(lineEnd.position.x, lineEnd.position.y);
Gizmos.DrawLine(VecLineStart, vecLineEnd);
Gizmos.DrawLine(leftDown, leftUp);
Gizmos.DrawLine(leftUp, RightUp);
Gizmos.DrawLine(RightUp, RigtDown);
Gizmos.DrawLine(RigtDown, leftDown);
}
private void OnGUI()
{
string content = "不在矩形内";
if (LineInRect(VecLineStart, vecLineEnd, rect))
content = "在矩形内";
GUILayout.Label(content);
content = "不相交";
if (LineIntersectRect(VecLineStart, vecLineEnd, rect))
content = "相交";
GUILayout.Label(content);
GUILayout.Label("RightUp:[" + RightUp + "]
RigtDown:[" + RigtDown);
}
// 线是否在矩形内
bool LineInRect(Vector2 lineStart, Vector2 lineEnd, Rect rect)
{
return rect.Contains(lineStart) || rect.Contains(lineEnd);
}
// 线与矩形是否相交
bool LineIntersectRect(Vector2 lineStart, Vector2 lineEnd, Rect rect)
{
if (LineIntersectLine(lineStart, lineEnd, leftDown, leftUp))
return true;
if (LineIntersectLine(lineStart, lineEnd, leftUp, RightUp))
return true;
if (LineIntersectLine(lineStart, lineEnd, RightUp, RigtDown))
return true;
if (LineIntersectLine(lineStart, lineEnd, RigtDown, leftDown))
return true;
return false;
}
// 线与线是否相交
bool LineIntersectLine(Vector2 l1Start, Vector2 l1End, Vector2 l2Start, Vector2 l2End)
{
return QuickReject(l1Start, l1End, l2Start, l2End) && Straddle(l1Start, l1End, l2Start, l2End);
}
// 快速排序。
true=通过， false=不通过
bool QuickReject(Vector2 l1Start, Vector2 l1End, Vector2 l2Start, Vector2 l2End)
{
float l1xMax = Mathf.Max(l1Start.x, l1End.x);
float l1yMax = Mathf.Max(l1Start.y, l1End.y);
float l1xMin = Mathf.Min(l1Start.x, l1End.x);
float l1yMin = Mathf.Min(l1Start.y, l1End.y);
float l2xMax = Mathf.Max(l2Start.x, l2End.x);
float l2yMax = Mathf.Max(l2Start.y, l2End.y);
float l2xMin = Mathf.Min(l2Start.x, l2End.x);
float l2yMin = Mathf.Min(l2Start.y, l2End.y);
if (l1xMax < l2xMin || l1yMax < l2yMin || l2xMax < l1xMin || l2yMax < l1yMin)
return false;
return true;
}
// 跨立实验
bool Straddle(Vector3 l1Start, Vector3 l1End, Vector3 l2Start, Vector3 l2End)
{
float l1x1 = l1Start.x;
float l1x2 = l1End.x;
float l1y1 = l1Start.y;
float l1y2 = l1End.y;
float l2x1 = l2Start.x;
float l2x2 = l2End.x;
float l2y1 = l2Start.y;
float l2y2 = l2End.y;
if ((((l1x1 - l2x1) * (l2y2 - l2y1) - (l1y1 - l2y1) * (l2x2 - l2x1)) *
((l1x2 - l2x1) * (l2y2 - l2y1) - (l1y2 - l2y1) * (l2x2 - l2x1))) > 0 ||
(((l2x1 - l1x1) * (l1y2 - l1y1) - (l2y1 - l1y1) * (l1x2 - l1x1)) *
((l2x2 - l1x1) * (l1y2 - l1y1) - (l2y2 - l1y1) * (l1x2 - l1x1))) > 0)
{
return false;
}
return true;
}

}

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