2013年11月25日星期一（DEMO5-3计算参数化直线和平面交点）

今天，以3D为主，

仍然一步步地进行。

首先加了个3D参数化直线，类似于参数化2D直线。

 

//参数化D直线

typedef struct PARMLINE3D_TYP

{

 

    POINT3D           p0;      //起点

    POINT3D           p1;      //终点

    VECTOR3D         v;       //方向向量p0->p1

}PARMLINE3D, * PARMLINE3D_PTR;

 

3D点积

float ddraw_math::VECTOR3D_DOT( VECTOR3D_PTR va, VECTOR3D_PTR vb )

{

    return ( ( va->x * vb->x ) + ( va->y * vb->y ) + ( va->z + vb->z ) );

}

增加一个可能：线在平面上

#define  PARM_LINE_INTERSECT_EVERYWHERE     3

 

int ddraw_math::Intersect_Parm_Lines3D_Plane3D(PARMLINE3D_PTR pline, PLANE3D_PTR plane, float * t, POINT3D_PTR pt )

{

    float plane_dot_line               = VECTOR3D_DOT( &pline->v, &plane->n );

    if ( fabs(plane_dot_line) <= EPSILON_E5 )

    {

         if( fabs( Compute_Point_In_Plane3D( & pline->p0, plane ) ) <= EPSILON_E5 )

             return PARM_LINE_INTERSECT_EVERYWHERE;

         else

             return PARM_LINE_NO_INTERSECT;

    }

 

    *t                             = - ( plane->n.x * pline->p0.x +plane->n.y * pline->p0.y +plane->n.z * pline->p0.z - plane->n.x * plane->n.x - plane->n.y * plane->n.y - plane->n.z * plane->n.z ) / plane_dot_line;

 

    pt->x                          = pline->p0.x + pline->v.x * ( *t );

    pt->y                          = pline->p0.y + pline->v.y * ( *t );

    pt->z                          = pline->p0.z + pline->v.z * ( *t );

 

 

 

 

    if ( ( * t >= 0 ) && ( * t <= 1 ) )

    {

         return ( PARM_LINE_INTERSECT_IN_SEGMENT );

    }

    else

    {

         return (PARM_LINE_INTERSECT_OUT_SEGMENT );

    }

}

计算参数形式3D直线

 

void ddraw_math::Compute_Parm_Line3D( PARMLINE3D_PTR p, float t, POINT3D_PTR pt )

{

    pt->x                          = p->p0.x+ p->v.x * t;

    pt->y                          = p->p0.y+ p->v.y * t;

    pt->z                          = p->p0.z+ p->v.z * t;

   

 

 

}

void ddraw_math   ::Init_Parm_Line3D( POINT3D_PTR p_init, POINT3D_PTR p_term, PARMLINE3D_PTR p )

{

    VECTOR3D_INIT( & ( p->p0 ), p_init );

    VECTOR3D_INIT( & ( p->p1), p_term );

    VECTOR3D_Build( p_init, p_term, & ( p->v));

 

}

void ddraw_math::VECTOR3D_Build( VECTOR3D_PTR init, VECTOR3D_PTR term, VECTOR3D_PTR result )

{

    result->x                      = term->x -init->x;

    result->y                      = term->y - init->y;

    result->z                      = term->z - init->z;

}