bool Ray::IntersectBox( Box3 a_box, matrix a_mat_transform )
{
// translate by position
a_mat_transform = a_mat_transform * matrix::Translation( a_box.GetCenter() );
v3 halfsize = a_box.Size()*0.5f;
float tmin = -FLT_MAX;
float tmax = FLT_MAX;
v4 nmin;
v4 nmax;
const v4 p = a_mat_transform.w - v4(m_pos,1.0f);
for ( size_t i=0; i!=3; ++i )
{
v4 box_basis_vector = a_mat_transform[i];
const float e = dot( box_basis_vector, p );
float f = dot( box_basis_vector, v4(m_dir,0.0f) );
if ( fabs(f) > EPSILON )
{
f = 1.0f/f;
float t1 = ( e + halfsize[i] ) * f;
float t2 = ( e - halfsize[i] ) * f;
float flip = 1.f;
if ( t1 > t2 )
{
// swap
float tmp = t1;
t1 = t2;
t2 = tmp;
flip = -flip;
}
if ( t1 > tmin ) { tmin = t1; nmin = a_mat_transform[i] * flip; }
if ( t2 < tmax ) { tmax = t2; nmax =-a_mat_transform[i] * flip; }
if ( tmin > tmax ) return false;
if ( tmax < 0.f ) return false;
}
else if ( ( ( -e - halfsize[i] ) > 0.f ) ||
( ( -e + halfsize[i] ) < 0.f ) )
{
// ray parallel to the stab
return false;
}
}
if ( tmin > 0.f )
return NewHit( tmin, nmin.xyz() );
return NewHit( tmax, nmax.xyz() );
}
