// Try to make up a 1st derivative if one is zero length
static void CookDerivativesHelper( ON_3dVector& du, ON_3dVector& dv, ON_3dVector& duu, ON_3dVector& duv, ON_3dVector& dvv)
{
bool du_ok = du.LengthSquared() > ON_SQRT_EPSILON;
bool dv_ok = dv.LengthSquared() > ON_SQRT_EPSILON;
if( !du_ok || !dv_ok)
{
ON_3dVector normal;
bool normal_ok = ON_EvNormal( 0, du, dv, duu, duv, dvv, normal ) ? true : false;
if( normal_ok)
normal_ok = normal.LengthSquared() > ON_SQRT_EPSILON;
if( normal_ok)
{
if(( !du_ok) && ( dv_ok && normal_ok))
{
du = ON_CrossProduct( dv, normal);
du_ok = du.Unitize();
du *= (0.00390625*dv.Length());
}
if( du_ok && ( !dv_ok) && normal_ok)
{
dv = ON_CrossProduct( normal, du);
dv_ok = dv.Unitize();
dv *= (0.00390625*du.Length());
}
}
}
}
bool ON_Line::ClosestPointTo( const ON_3dPoint& point, double *t ) const
{
bool rc = false;
if ( t ) {
const ON_3dVector D = Direction();
const double DoD = D.LengthSquared();
if ( DoD > 0.0 ) {
if ( point.DistanceTo(from) <= point.DistanceTo(to) ) {
*t = ((point - from)*D)/DoD;
}
else {
*t = 1.0 + ((point - to)*D)/DoD;
}
rc = true;
}
else {
*t = 0.0;
}
}
return rc;
}