java - 线相交方法无法正常工作

Question

我正在研究一些 vector 数学，我需要计算多边形的法 vector 。我的代码:

    //p is a parameter, is a Vec2, second point on first line
    double[][] vert = getVerticies(); //[any length, # of verticies][2]
    for(int i = 0; i < vert.length; i++) {
        Vec2 cm = Vec2.ZERO_VEC;//first point on first line, always is <0, 0> as it is the origin
        Vec2 rcm = getCM(); // just used to get relative positions.
        Vec2 v1 = cm.sub(new Vec2(vert[i])); //the first point in one of all edges of the shape, second line
        Vec2 v2 = cm.sub(new Vec2(i == vert.length - 1 ? vert[0] : vert[i + 1])); // the second point on the second  line.
        double den = (v2.getY() - v1.getY()) * (p.getX() - cm.getX()) - (v2.getX() - v1.getX()) * (p.getY() - cm.getY());
        if(den == 0D) {
            continue;
        }
        double a = ((v2.getX() - v1.getX()) * (cm.getY() - v1.getY()) - (v2.getY() - v1.getY()) * (cm.getX() - v1.getX())) / den;
        double b = ((p.getX() - cm.getX()) * (cm.getY() - v1.getY()) - (p.getY() - cm.getY()) * (cm.getX() - v1.getX())) / den;
        if(a >= 0D && a <= 1D && b >= 0D && b <= 1D) {
            Vec2 mid = v2.add(v2.sub(v1).scale(0.5D)); //this is just normal vector calculation stuff, I know the error isn't here, as if it was, it would return a non-unit-scale vector.
            return mid.uscale(); //hats the vector, returns
        }
    }
    return p; // return the parameter, second point on first line, used as a contingency, should never actually run, as the first line is fully contained in the lines were testing against

我已经进行了一些调试，但我只是没有看到发生了什么。谁能告诉我我的数学有什么问题吗？它似乎运行得很好，但数学似乎不太正确。我使用此代码的目标是确定我的线相交的两个顶点的索引。

Answer 1

哎呀，通过尝试解释它弄清楚了。我需要进行光线追踪，或者使用光线相交测试。