bool ON_PolyEdgeCurve::EvSrfTangent(
double t,
bool bIsoDir,
ON_3dPoint& srfpoint,
ON_3dVector& srftangent,
ON_3dVector& srfnormal
) const
{
ON_3dPoint srfpt;
ON_3dVector du, dv, duu, duv, dvv;
bool rc = EvSrfDerivatives(t,srfpoint,du,dv,duu,duv,dvv);
if (rc )
rc = ON_EvNormal( 0, du, dv, duu, duv, dvv, srfnormal ) ? true : false;
if (rc)
{
int segment_index = SegmentIndex(t);
ON_PolyEdgeSegment* seg = SegmentCurve(segment_index);
if ( seg )
{
if ( bIsoDir && seg->IsoType() == ON_Surface::not_iso )
bIsoDir = false;
ON_3dVector crvtangent = TangentAt(t);
ON_3dVector binormal = ON_CrossProduct(crvtangent,srfnormal);
binormal.Unitize();
if ( seg->ReversedTrimDir() )
binormal.Reverse();
// at this point, binormal points "out" and is tangent
// to the surface.
if ( bIsoDir )
{
du.Unitize();
dv.Unitize();
double B_dot_du = binormal*du;
double B_dot_dv = binormal*dv;
if ( fabs(B_dot_dv) > fabs(B_dot_du) )
{
if (B_dot_dv < 0.0)
dv.Reverse();
srftangent = dv;
}
else
{
if (B_dot_du < 0.0)
du.Reverse();
srftangent = du;
}
}
else
srftangent = binormal;
if ( seg && seg->m_face && seg->m_face->m_bRev )
srfnormal.Reverse();
}
else
rc = false;
}
return rc;
}
ON_3dVector ON_Light::PerpindicularDirection() const
{
// returns a consistent vector perpendicular to the
// light's direction. This vector is useful for
// user interface display.
ON_3dVector dir = m_direction;
if ( !dir.IsValid() || !dir.Unitize() )
return ON_UNSET_VECTOR;
ON_3dVector xdir;
if ( IsLinearLight() || IsRectangularLight() )
{
xdir = m_length;
if ( xdir.IsValid() && xdir.Unitize() && fabs(xdir*dir) <= ON_SQRT_EPSILON )
return xdir;
}
if( dir.IsParallelTo( ON_zaxis, ON_DEGREES_TO_RADIANS * 3.0))
xdir = ON_CrossProduct( dir, ON_xaxis);
else
xdir = ON_CrossProduct( dir, ON_zaxis);
xdir.Unitize();
ON_3dVector ydir = ON_CrossProduct(dir,xdir);
ydir.Unitize();
ON_3dVector right;
switch(dir.MaximumCoordinateIndex())
{
case 0:
right = (fabs(xdir.y) > fabs(ydir.y)) ? xdir : ydir;
if ( right.y < 0.0 )
right.Reverse();
break;
case 1:
case 2:
right = (fabs(xdir.x) > fabs(ydir.x)) ? xdir : ydir;
if ( right.x < 0.0 )
right.Reverse();
break;
default:
right = xdir;
break;
}
if ( right[right.MaximumCoordinateIndex()] < 0.0 )
right.Reverse();
return right;
}
ON_BOOL32 ON_ArcCurve::SetStartPoint(ON_3dPoint start_point)
{
if (IsCircle())
return false;
ON_BOOL32 rc = false;
if ( m_dim == 3 || start_point.z == 0.0 )
{
ON_3dPoint P;
ON_3dVector T;
double t = Domain()[1];
Ev1Der( t, P, T );
T.Reverse();
ON_Arc a;
rc = a.Create( P, T, start_point );
if ( rc )
{
a.Reverse();
m_arc = a;
}
else {
ON_3dPoint end_point = PointAt(Domain()[1]);
if (end_point.DistanceTo(start_point) < ON_ZERO_TOLERANCE*m_arc.Radius()){
//make arc into circle
m_arc.plane.xaxis = end_point - m_arc.Center();
m_arc.plane.xaxis.Unitize();
m_arc.plane.yaxis = ON_CrossProduct(m_arc.Normal(), m_arc.plane.xaxis);
m_arc.plane.yaxis.Unitize();
m_arc.SetAngleRadians(2.0*ON_PI);
rc = true;
}
}
}
return rc;
}