/// <summary>
/// 计算两条二维线段的交点
/// </summary>
/// <param name="other"></param>
/// <param name="intersectPoint">线段交点</param>
/// <returns></returns>
public LineCrossState Intersection(Line2D other, out Vector2 intersectPoint)
{
intersectPoint.x = intersectPoint.y = float.NaN;
if (!UMath.IsLineCross(this, other))
{
return(LineCrossState.NOT_CROSS);
}
double A1, B1, C1, A2, B2, C2;
A1 = point2.y - point1.y;
B1 = point1.x - point2.x;
C1 = point2.x * point1.y - point1.x * point2.y;
A2 = other.point2.y - other.point1.y;
B2 = other.point1.x - other.point2.x;
C2 = other.point2.x * other.point1.y - other.point1.x * other.point2.y;
if (UMath.IsEqualZero(A1 * B2 - B1 * A2))
{
if (UMath.IsEqualZero((A1 + B1) * C2 - (A2 + B2) * C1))
{
return(LineCrossState.COLINE);
}
else
{
return(LineCrossState.PARALLEL);
}
}
intersectPoint.x = (float)((B2 * C1 - B1 * C2) / (A2 * B1 - A1 * B2));
intersectPoint.y = (float)((A1 * C2 - A2 * C1) / (A2 * B1 - A1 * B2));
return(LineCrossState.CROSS);
}
/// <summary>
/// 三角形的外接圆
/// </summary>
/// <param name="p1"></param>
/// <param name="p2"></param>
/// <param name="p3"></param>
/// <returns>Circle</returns>
public static Circle TriangleCircumscribedCircle(Triangle triangle)
{
if (!UMath.IsEqualZero(triangle.point1.y - triangle.point2.y) || !UMath.IsEqualZero(triangle.point2.y - triangle.point3.y))
{
double yc, xc;
float m1 = -(triangle.point2.x - triangle.point1.x) / (triangle.point2.y - triangle.point1.y);
float m2 = -(triangle.point3.x - triangle.point2.x) / (triangle.point3.y - triangle.point2.y);
double mx1 = (triangle.point1.x + triangle.point2.x) / 2.0;
double mx2 = (triangle.point2.x + triangle.point3.x) / 2.0;
double my1 = (triangle.point1.y + triangle.point2.y) / 2.0;
double my2 = (triangle.point2.y + triangle.point3.y) / 2.0;
if (UMath.IsEqualZero(triangle.point1.y - triangle.point2.y))
{
xc = (triangle.point2.x + triangle.point1.x) / 2.0;
yc = m2 * (xc - mx2) + my2;
}
else if (UMath.IsEqualZero(triangle.point3.y - triangle.point2.y))
{
xc = (triangle.point3.x + triangle.point2.x) / 2.0;
yc = m1 * (xc - mx1) + my1;
}
else
{
xc = (m1 * mx1 - m2 * mx2 + my2 - my1) / (m1 - m2);
yc = m1 * (xc - mx1) + my1;
}
double dx = triangle.point2.x - xc;
double dy = triangle.point2.y - yc;
double rsqr = dx * dx + dy * dy;
double r = Math.Sqrt(rsqr);
return(new Circle(new Vector2((float)xc, (float)yc), (float)r));
}
return(new Circle(Vector2.zero, 0));
}
/// <summary>
/// 判断点与直线的关系
/// </summary>
/// <param name="point">判断点</param>
/// <returns></returns>
public PointSideRelation ClassifyPoint(Vector2 point)
{
if (point == m_point1 || point == m_point2)
{
return(PointSideRelation.ON_LINE);
}
Vector2 vectorA = m_point2 - m_point1;
Vector2 vectorB = point - m_point1;
float crossResult = UMath.CrossProduct(vectorA, vectorB);
if (UMath.IsEqualZero(crossResult))
{
return(PointSideRelation.ON_LINE);
}
else if (crossResult < 0)
{
return(PointSideRelation.RIGHT_SIDE);
}
else
{
return(PointSideRelation.LEFT_SIDE);
}
}
