/// <summary>
/// 判断两条线段是否相交
/// 现在有线段AB和线段CB
//用线段AB的方向和C，D两点分别做差乘比较。如果C,D在同侧则return跳出
//用线段CD的方向和A，B两点分别做差乘比较。如果A,B在同侧则return跳出
//最终返回相交
/// </summary>
/// <param name="a"></param>
/// <param name="b"></param>
/// <param name="c"></param>
/// <param name="d"></param>
/// <returns></returns>
static bool IsTwoSegmentIntersection(Vector2L a2d, Vector2L b2d, Vector2L c2d, Vector2L d2d)
{
Vector3L a = new Vector3L(a2d.x, 0, a2d.y);
Vector3L b = new Vector3L(b2d.x, 0, b2d.y);
Vector3L c = new Vector3L(c2d.x, 0, c2d.y);
Vector3L d = new Vector3L(d2d.x, 0, d2d.y);
var crossA = FixPointMath.Sign(Vector3L.Cross(d - c, a - c).y);
var crossB = FixPointMath.Sign(Vector3L.Cross(d - c, b - c).y);
if (FixPointMath.Approximately(crossA, crossB))
{
return(false);
}
var crossC = FixPointMath.Sign(Vector3L.Cross(b - a, c - a).y);
var crossD = FixPointMath.Sign(Vector3L.Cross(b - a, d - a).y);
if (FixPointMath.Approximately(crossC, crossD))
{
return(false);
}
return(true);
}
public static bool Point2dWithLine2d(Vector2L point, Line2d line2d)
{
// Find the slope
FloatL dy = (line2d.m_point2.y - line2d.m_point1.y);
FloatL dx = (line2d.m_point2.x - line2d.m_point1.x);
FloatL M = dy / dx;
// Find the Y-Intercept
FloatL B = line2d.m_point1.y - M * line2d.m_point1.x;
// Check line equation
return(FixPointMath.Approximately(point.y, M * point.x + B));
}
