void AddPoint(float cX, float cY) {
        cX = 2.0f * cX / windowWidth - 1;    // flip y axis
        cY = 1.0f - 2.0f * cY / windowHeight;
        glBindBuffer(GL_ARRAY_BUFFER, vbo);
        if (nVertices >= 10000) return;

        vec4 wVertex = vec4(cX, cY, 0, 1) * camera.Pinv() * camera.Vinv();
        // fill interleaved data
        vertexData[5 * nVertices] = wVertex.v[0];
        vertexData[5 * nVertices + 1] = wVertex.v[1];
        vertexData[5 * nVertices + 2] = 1; // red
        vertexData[5 * nVertices + 3] = 1; // green
        vertexData[5 * nVertices + 4] = 0; // blue
        nVertices++;
        // copy data to the GPU
        glBufferData(GL_ARRAY_BUFFER, nVertices * 5 * sizeof(float), vertexData, GL_DYNAMIC_DRAW);
    }

    void Draw() {
        if (nVertices > 0) {
            mat4 VPTransform = camera.V() * camera.P();

            int location = glGetUniformLocation(shaderProgram, "MVP");
            if (location >= 0) glUniformMatrix4fv(location, 1, GL_TRUE, VPTransform);
            else printf("uniform MVP cannot be set\n");

            glBindVertexArray(vao);
            glDrawArrays(GL_LINE_STRIP, 0, nVertices);
        }
    }
};
LineStrip lineStrip;

class Lagrange {
    std::vector<vec2> MainPontok;

    int nPoints = 10;

public:

    void AddPoint(float x, float y) {
        MainPontok.push_back(vec2(x,y));


    }

    void Addteszt() {

        MainPontok.push_back(vec2(-9, 5));
        MainPontok.push_back(vec2(-4, 2));
        MainPontok.push_back(vec2(-1, -2));
        MainPontok.push_back(vec2(7, 9));
        calculatePontteszt();

    }

    void calculatePontteszt()
    {

        for (float i = -9; i < 7; i+=0.1)
        {
            lineStrip.AddPoint(i,L(i));
        }



    }

    void PointMagic() {
        float cX; float cY;
        for (size_t i = 1; i < MainPontok.size(); i++)
        {
            float egyseg=MainPontok[i].x - MainPontok[i - 1].x / nPoints;
            for (int j = 0; j < nPoints; j++)
            {


                lineStrip.AddPoint(MainPontok[i].x + (j*egyseg), L(MainPontok[i].x + (j*egyseg)));

            }
        }

    }




    float   L(float x) {
        float ret = 0;
        for (size_t i = 0; i < MainPontok.size(); i++)
        {
            ret += kisL(x, i)*MainPontok[i].y;

        }
        printf("%f\t%f\n", x, ret);
        return ret;
    }

    float kisL(float x, int j) {
        float ret = 1;
        for (size_t i = 0; i < MainPontok.size(); i++)
        {
            if (i != j)
            {
                ret *= (x - MainPontok[i].x) / (MainPontok[j].x - MainPontok[i].x);
            }

        }
        return ret;

    }


    /*void WritePoints() {
        for (size_t i = 0; i < AllPoint.size(); i++)
        {
            printf("%f\t%f\n", AllPoint[i].x, AllPoint[i].y);

        }


    }*/
};