bool CBasePoly::InsideDiagonal( uint32 a, uint32 b )
{
uint32 a_plus_1, a_minus_1;
a_plus_1 = m_Indices.NextI( a );
a_minus_1 = m_Indices.PrevI( a );
if( LeftOn(a_minus_1, a, a_plus_1) )
{
return Left(a, b, a_minus_1) && Left(b, a, a_plus_1);
}
else
{
return !( LeftOn(a, b, a_plus_1) && LeftOn(b, a, a_minus_1) );
}
}
/*---------------------------------------------------------------------
Returns TRUE iff the diagonal (a,b) is strictly internal to the
polygon in the neighborhood of the a endpoint.
---------------------------------------------------------------------*/
bool InCone( tVertex a, tVertex b )
{
tVertex a0,a1; /* a0,a,a1 are consecutive vertices. */
a1 = a->next;
a0 = a->prev;
/* If a is a convex vertex ... */
if( LeftOn( a->v, a1->v, a0->v ) )
return Left( a->v, b->v, a0->v )
&& Left( b->v, a->v, a1->v );
/* Else a is reflex: */
return !( LeftOn( a->v, b->v, a1->v )
&& LeftOn( b->v, a->v, a0->v ) );
}
