光线与三角的求交代码

eiBool eiTriangle::intersect(eiRay *ray, eiObject *po, eiFloat & oldt,
                             eiPrimitive* & ret_pri, eiFloat *cust_data, HitParam *hparam)
{
    if    ( clip == EI_BSP_PRIMITIVE &&
            ( oldt == 0.0f || ray_box( ray->src, hparam->hitPoint ) )
        )
    {
        //compute intersecting point

        eiFloat vnd = dot(normal , ray->dir);

        if(ray->type == RAY_SHADOW)
            vnd = - vnd;
            
        if( vnd < 0.0f || po->material->doubleSide )
        {
            eiFloat        t,td1,td2,td3;
            eiVector    tmpIntersection;

            if(ray->type == RAY_SHADOW)
                t = ( dot( normal , ray->src) + d ) / vnd;
            else
                t = -( dot( normal , ray->src) + d ) / vnd;

            if(t < 0.0f)
                return false;

            tmpIntersection = add(ray->src, mulvf(ray->dir,t));

            //make sure intersection in bound box 

            if(!is_pos_in_box(tmpIntersection, box))
                return false;

            //near and far clipping

            if(ray->type == RAY_EYE && !near_far_clip(tmpIntersection))
                return false;

            //is in triangular area

            td1 = dot(tmpIntersection , la) + d1;

            if(td1 < 0.0f || td1 > 1.0f)
                return false;

            td2 = dot(tmpIntersection , lb) + d2;

            if(td2 < 0.0f || td2 > 1.0f)
                return false;

            td3 = dot(tmpIntersection , lc) + d3;

            if(td3 < 0.0f || td3 > 1.0f)
                return false;

            //affect shadow factor

            if(ray->type == RAY_SHADOW)
                hparam->shadow_factor *= 1.0f - po->material->opacity;

            //find nearest hit point

            if(oldt == 0.0f || t < oldt)
            {
                hparam->hitPoint = tmpIntersection;
                hparam->hitObj = po;
                ret_pri = this;
                oldt = t;

                //fill custom data

                cust_data[0] = td1;
                cust_data[1] = td2;
                cust_data[2] = td3;

                return true;
            }
        }
    }

    return false;
}