Hi there,
i am currently implementing a simple ray tracer in c++. I have a class named OrthonormalBasis, which generates three orthogonal unit vectors from one or two specified vectors, for example:
void
OrthonormalBasis::init_from_u ( const Vector& u )
{
Vector n(1,0,0);
Vector m(0,1,0);
u_ = unify(u);
v_ = cross(u_,n);
if ( v_.length() < ONB_EPSILON )
v_ = cross(u_,m);
w_ = cross(u_,v_);
}
I am testing all my methods with the Unittest++ framework. The Problem is, that there is more than one possible solution for a valid orthonormal basis. For example this test:
TEST ( orthonormalbasis__should_init_from_u )
{
Vector u(1,0,0);
OrthonormalBasis onb;
onb.init_from_u(u);
CHECK_EQUAL( Vector( 1, 0, 0 ), onb.u() );
CHECK_EQUAL( Vector( 0, 0, 1 ), onb.v() );
CHECK_EQUAL( Vector( 0, 1, 0 ), onb.w() );
}
sometimes it succeeds, sometimes it fails, because the vectors v and w could also have a negative 1, and still represent a valid orthonormal basis. Is there a way to specify multiple expected values? Or do you know another way to do that?
It is important, that i get the actual and expected values printed to the stdout, in order to debug the methods so this solution won't do the job:
TEST ( orthonormalbasis__should_init_from_u )
{
Vector u(1,0,0);
OrthonormalBasis onb;
onb.init_from_u(u);
CHECK_EQUAL( Vector( 1, 0, 0 ), onb.u() );
CHECK(
Vector( 0, 0, 1 ) == onb.v() ||
Vector( 0, 0,-1 ) == onb.v() );
CHECK(
Vector( 0, 1, 0 ) == onb.w() ||
Vector( 0,-1, 0 ) == onb.w() );
}