#include "XMathLib.h"
#include "XGeomLib.h"
#include "XGVolume.h"
using namespace XMathLib;


namespace XGeomLib
{
    __inline bool isSameDir(XVector3D& v1,XVector3D& v2)
    {
        float t = v1.x * v2.x;
        if( t == 0)
        {
            if(v1.x !=0 || v2.x !=0)
                return false;
        }
        if( t < 0)
            return false;

        t = v1.y * v2.y;
        if( t == 0)
        {
            if(v1.y !=0 || v2.y !=0)
                return false;
        }
        if( t < 0)
            return false;

        t = v1.z * v2.z;
        if( t == 0)
        {
            if(v1.z !=0 || v2.z !=0)
                return false;
        }
        if( t < 0)
            return false;

        return true;
    }
    //線和面的交
    ///2004 - 6 - 24 基本測試
    bool InterSection(XRay& ray,XPlan& plan,XPoint& point,float & t)
    {
        t = 0;

        /***

        -D - P0 * N(A,B,C)
        t = --------------------
        d * N(A,B,C)

        其中D 為平面方程中的D,
        P0為射線的起點。而 d 為射線的方向

        **/
        t= -(plan.D  + ray.m_Point.x * plan.A + ray.m_Point.y * plan.B + ray.m_Point.z * plan.C);
        float t2 = (ray.m_Dir.x * plan.A + ray.m_Dir.y * plan.B + ray.m_Dir.z * plan.C) ;

        if(t2 == 0.00)
            return false;

        t /= t2;


        //求出交點
        point  = ray.m_Point + ray.m_Dir * t;

        if( t < 0)
            return false;

        return true;
    }

    /**************************************************************************
    求三角形和射線的交點。

    2004-  6 -27 日建立
    2004 - 6 -27 日初步測試。
    ***************************************************************************/
    bool    InterSection(XRay& ray,XTriangle& tri,XPoint& point,float & t)
    {

        XVector3D v1 = tri.m_points[1] - tri.m_points[0];
        XVector3D v2 = tri.m_points[2] - tri.m_points[0];

        XVector3D n = v1.cp(v2);
        /**********************************************************************
        ray = p0 + D * t
        Tri : p1 - p3

        (P2-P1) X (P3-P1) = N 

        N * (P - P1) = 0  ===>
        N * (P0 + D * t - P1)  = 0

        ==>

        N * (P0 - P1) + N * D * t = 0;
        (P1-P0) * N
        t = ----------------------
        D * N
        ******************************************************************/
        t = n.dp(tri.m_points[0] - ray.m_Point);
        t /= (ray.m_Dir.dp(n));
        if( t < 0)
            return false;

        //求出交點
        point  = ray.m_Point + ray.m_Dir * t;

        //判斷點是不是在三角內部
        v1 =  tri.m_points[0] - point ;
        v2 =  tri.m_points[1] - point ;

        XVector3D v3 = tri.m_points[2] - point ;

        v1.cp(v2,n);
        XVector3D n1,n2;
        v2.cp(v3,n1);
        v3.cp(v1,n2);

        if(n.isZero())
            return true;
        if(n1.isZero())
            return true;
        if(n2.isZero())
            return true;

        if(false == isSameDir(n2,n))
            return false;

        return isSameDir(n1,n2);
    }

    /**************************************************************************
    求三角形和射線的交點。能求出三個參數。

    2004-  6 -27 日建立
    2004 - 6 -27 日初步測試。
    ***************************************************************************/
    bool InterSection(XRay& ray,XTriangle& tri,XPoint& point,float& t, float& u, float& v )
    {
        // Find vectors for two edges sharing vert0
        /***

        三角形為 v1,v2,v3
        兩條邊為  e1 = v2-v1   e2 = v3 - v1
        射線為    ray = p0 + d * t
        三角形內部的一點 p = v1 + u * e1 + v * e2  (  u+v<1)

        所以： 
        v1 + u * e1 + v * e2 = p0 + d * t              ===>
        u * e1 + v * e2 - t * d = p0 - v1              ===>
        - t * d  + v * e2 +  u * e1  = p0 - v1         ===>

        |  d.x   d.y    d.z  |
        [-t,v,u]  |  e2.x  e2.y   e2.z |   = p0 - p1  ===>
        |  e1.x  e1.y   e1.z |


        [-t,v,u] * M  = p0 - p1 ;


        [-t,v,u] = (p0 - p1) * Inv(M);


        t  = (p0 - p1) * e1 X e2 / Det(M) =  (p0 - p1) X e1 * e2 / Det(M)

        v  = (p0 - p1) * e1 X d  / Det(M) =  (p0 - p1) X e1 * d  / Det(M)

        u  = (p0 - p1) * d X e2  / Det(M)

        **/
        XVector3D e1  = tri.m_points[1] - tri.m_points[0];
        XVector3D e2  = tri.m_points[2] - tri.m_points[0];


        //求出矩陣 M 的 det(M)。并記錄 d x e2;
        XVector3D vCP_dir_e2;
        ray.m_Dir.cp(e2,vCP_dir_e2);

        //得到矩陣的行列式的值
        float det = e1.dp(vCP_dir_e2);

        //保存 (p0 - p1) 
        XVector3D v_p0_p1;

        //為了判斷方便。det = abs(det) 
        if( det > 0 )
        {
            v_p0_p1 = ray.m_Point - tri.m_points[0];
        }
        else
        {
            v_p0_p1 = tri.m_points[0] - ray.m_Point  ;
            det = -det;
        }

        if( det < 0.0000001f )
            return false;

        // u  = (p0 - p1) * d X e2  / Det(M)  Det(M)以后再除
        u  = v_p0_p1.dp(vCP_dir_e2);
        if( u < 0.0f || u > det )
            return false;


        // 保存 (p0 - p1) X e1
        XVector3D vCP_p0p1_e1;
        v_p0_p1.cp(e1,vCP_p0p1_e1);

        // v  = (p0 - p1) * e1 X d  / Det(M) =  (p0 - p1) X e1 * d  / Det(M)
        // Det(M)以后再除
        v = ray.m_Dir.dp(vCP_p0p1_e1);
        if( v < 0.0f || u + v > det )
            return false;

        // Calculate t, scale parameters, ray intersects triangle
        t =  e2.dp(vCP_p0p1_e1);
        float fInvDet = 1.0f / det;
        t *= fInvDet;
        u *= fInvDet;
        v *= fInvDet;
        point = ray.m_Point + ray.m_Dir*t;
        return true;
    }

    //線段和面的相交
    bool  InterSection(XLineSegment& lineSeg,XPlan& plan,XPoint& point,float & t)
    {
        return 1;;
    }
    bool  InterSection(XLineSegment& lineSeg,XTriangle& tri,XPoint& point,float & t)
    {
        return 1;;
    }

    //線和線的相交
    float InterSection(XRay& ray1,XRay& ray2,XPoint& point)
    {


        return 1;;
    }
    float InterSection(XRay& ray,XLineSegment& lineSeg,XPoint& point)
    {

        return 1;;
    }
    float InterSection(XLineSegment& lineSeg1,XLineSegment& lineSeg2,XPoint& point)
    {

        return 1;;
    }

    //點是不是在三角形和面上
    float InterSection(XPoint& point ,XTriangle& tri)
    {

        return 1;;
    }
    float InterSection(XPoint& point ,XPolygon& polygon)
    {

        return 1;;
    }

};