向量叉乘判断两点是否在线段同侧

//两点是否在线段同侧
public static bool IsTwoPointSameSideOfSegment(Vector2 a, Vector2 b, Vector2 p1, Vector2 p2)
{
    var a_p1 = p1 - a;
    var ab = b - a;
    float cross1 = a_p1.x * ab.y - a_p1.y * ab.x;
    if (Mathf.Approximately(cross1, 0)) //p1与线段ab共线
        return true;

    var a_p2 = p2 - a;
    float cross2 = a_p2.x * ab.y - a_p2.y * ab.x;
    if (Mathf.Approximately(cross2, 0)) //p2与线段ab共线
        return true;

    var result = cross1 * cross2;
    return result > 0; //叉乘结果同符号, 则表示同侧
}