/// <summary>
/// ///计算pos到直线(lineSt, lineEnd)的最短距离
/// </summary>
/// <param name="pos"></param>
/// <param name="lineSt"></param>
/// <param name="lineEnd"></param>
/// <param name="lineIsSegment">是否为线段</param>
/// <returns></returns>
public static double LinePointDistance(Vector2_DW lineSt, Vector2_DW lineEnd, Vector2_DW pos, bool lineIsSegment)
{
double disRet = 0;
if (lineIsSegment == false)
{
disRet = Vector2_DW.Cross(lineSt, lineEnd, pos) / Vector2_DW.Distance(lineSt, lineEnd);
}
else
{
Vector2_DW ab = lineEnd - lineSt;
Vector2_DW bc = pos - lineEnd;
Vector2_DW ac = pos - lineSt;
if (Vector2_DW.Dot(ab, bc) > 0)//pos在lineEnd外侧
{
disRet = Vector2_DW.Distance(pos, lineEnd);
}
else if (Vector2_DW.Dot(ab, ac) > 0)//pos在lineEnd外侧
{
disRet = Vector2_DW.Distance(pos, lineSt);
}
else//pos在lineSt与lineEnd之间
{
disRet = Vector2_DW.Cross(lineSt, lineEnd, pos) / Vector2_DW.Distance(lineSt, lineEnd);
}
}
return(Math.Abs(disRet));
}
/// <summary>
/// 判断点pt是否在直线上
/// </summary>
/// <param name="pt"></param>
/// <param name="lnSt"></param>
/// <param name="lnEnd"></param>
/// <param name="isSegment">是否为直线段</param>
/// <returns></returns>
public static bool IsPointOnLine(Vector2_DW pt, Vector2_DW lnSt, Vector2_DW lnEnd, bool isSegment)
{
//设点为Q，线段为P1P2 ，判断点Q在该线段上的依据是：( Q - P1 ) × ( P2 - P1 ) = 0 且 Q 在以 P1，P2为对角顶点的矩形内。前者保证Q点在直线P1P2上，后者是保证Q点不在线段P1P2的延长线或反向延长线上
//My Method:设点为Q，线段为P1P2 ，判断点Q在该线段上的依据是：( Q - P1 ) × ( P2 - P1 ) = 0 且 Q 到p1p2的距离==0。前者保证Q点在直线P1P2上，后者是保证Q点不在线段P1P2的延长线或反向延长线上
Vector2_DW vec1 = pt - lnSt;
Vector2_DW vec2 = pt - lnEnd;
if (IsZero(Vector2_DW.Cross(vec1, vec2)) == true)
{
if (IsZero(LinePointDistance(lnSt, lnEnd, pt, isSegment)))
{
return(true);
}
}
return(false);
}
/// <summary>
/// 判断直线段与矩形是否相交(注:当线段全部在矩形内,也认为相交)
/// 1,线段端点是否在矩形内,在,true
/// 2,线段包围框是否和矩形相交,否,false
/// 3,矩形四个顶点是否在线段两侧,在true,不在,false
/// </summary>
/// <param name="lStScreen"></param>
/// <param name="lEndScreen"></param>
/// <param name="bx"></param>
/// <returns></returns>
public static bool LineSegmenXBox(Vector2_DW lStScreen, Vector2_DW lEndScreen, Box2D bx)
{
if (ToolsMath_DW.PtInBox(bx, lStScreen) &&
ToolsMath_DW.PtInBox(bx, lEndScreen))
{
return(true);
}
Box2D bxLine = ToolsMath_DW.GetLineMinBox(lStScreen, lEndScreen);
if (!ToolsMath_DW.BoxXBox(bx, bxLine))
{
return(false);
}
Vector2_DW vecLn = lStScreen - lEndScreen;
Vector2_DW vBxLeftUpper = bx._min - lEndScreen;
Vector2_DW vBxRightTop = (new Vector2_DW(bx._max.X, bx._min.Y)) - lEndScreen;
Vector2_DW vBxRightBtm = bx._max - lEndScreen;
Vector2_DW vBxLeftBtm = (new Vector2_DW(bx._min.X, bx._max.Y)) - lEndScreen;
double f1 = Vector2_DW.Cross(vecLn, vBxLeftUpper);
double f2 = Vector2_DW.Cross(vecLn, vBxRightTop);
double f3 = Vector2_DW.Cross(vecLn, vBxRightBtm);
double f4 = Vector2_DW.Cross(vecLn, vBxLeftBtm);
if ((f1 >= 0 && f2 >= 0 && f3 >= 0 && f4 >= 0)
||
(f1 <= 0 && f2 <= 0 && f3 <= 0 && f4 <= 0))
{
return(false);
}
else
{
return(true);
}
}
