ON_BOOL32 ON_PlaneSurface::GetSpanVector( int dir, double* s ) const
{
ON_Interval d = Domain(dir);
s[0] = d.Min();
s[1] = d.Max();
return d.IsIncreasing();
}
ON_BOOL32 ON_Surface::GetParameterTolerance( // returns tminus < tplus: parameters tminus <= s <= tplus
int dir,
double t, // t = parameter in domain
double* tminus, // tminus
double* tplus // tplus
) const
{
ON_BOOL32 rc = false;
ON_Interval d = Domain( dir );
if ( d.IsIncreasing() )
rc = ON_GetParameterTolerance( d.Min(), d.Max(), t, tminus, tplus );
return rc;
}
ON_Surface::ISO
ON_Surface::IsIsoparametric( const ON_BoundingBox& bbox ) const
{
ISO iso = not_iso;
if ( bbox.m_min.z == bbox.m_max.z ) {
const double ds = bbox.m_max.x - bbox.m_min.x;
const double dt = bbox.m_max.y - bbox.m_min.y;
double a, b, s0, s1, t0, t1;
ON_Interval d = Domain(0);
s0 = d.Min();
s1 = d.Max();
d = Domain(1);
t0 = d.Min();
t1 = d.Max();
double stol = (s1-s0)/32.0;
double ttol = (t1-t0)/32.0;
if ( s0 < s1 && t0 < t1 && ( ds <= stol || dt <= ttol) )
{
if ( ds*(t1-t0) <= dt*(s1-s0) )
{
// check for s = constant iso
if ( bbox.m_max.x <= s0+stol )
{
// check for west side iso
GetParameterTolerance( 0, s0, &a, &b);
if ( a <= bbox.m_min.x && bbox.m_max.x <= b )
iso = W_iso;
}
else if ( bbox.m_min.x >= s1-stol )
{
// check for east side iso
GetParameterTolerance( 0, s1, &a, &b);
if ( a <= bbox.m_min.x && bbox.m_max.x <= b )
iso = E_iso;
}
if ( iso == not_iso && (s0 < bbox.m_max.x || bbox.m_min.x < s1) )
{
// check for interior "u = constant" iso
GetParameterTolerance( 0, 0.5*(bbox.m_min.x+bbox.m_max.x), &a, &b);
if ( a <= bbox.m_min.x && bbox.m_max.x <= b )
iso = x_iso;
}
}
else
{
// check for t = constant iso
if ( bbox.m_max.y <= t0+ttol )
{
// check for south side iso
GetParameterTolerance( 1, t0, &a, &b);
if ( a < bbox.m_min.y && bbox.m_max.y <= b )
iso = S_iso;
}
else if ( bbox.m_min.y >= t1-ttol )
{
// check for north side iso
GetParameterTolerance( 1, t1, &a, &b);
if ( a < bbox.m_min.y && bbox.m_max.y <= b )
iso = N_iso;
}
if ( iso == not_iso && (t0 < bbox.m_max.x || bbox.m_min.x < t1) )
{
// check for interior "t = constant" iso
GetParameterTolerance( 1, 0.5*(bbox.m_min.y+bbox.m_max.y), &a, &b);
if ( a < bbox.m_min.y && bbox.m_max.y <= b )
iso = y_iso;
}
}
}
}
return iso;
}
ON_BOOL32
ON_Surface::EvNormal( // returns false if unable to evaluate
double s, double t, // evaluation parameters (s,t)
ON_3dPoint& point, // returns value of surface
ON_3dVector& ds, // first partial derivatives (Ds)
ON_3dVector& dt, // (Dt)
ON_3dVector& normal, // unit normal
int side, // optional - determines which side to evaluate from
// 0 = default
// 1 from NE quadrant
// 2 from NW quadrant
// 3 from SW quadrant
// 4 from SE quadrant
int* hint // optional - evaluation hint (int[2]) used to speed
// repeated evaluations
) const
{
// simple cross product normal - override to support singular surfaces
ON_BOOL32 rc = Ev1Der( s, t, point, ds, dt, side, hint );
if ( rc ) {
const double len_ds = ds.Length();
const double len_dt = dt.Length();
// do not reduce the tolerance used here - there is a retry in the code
// below.
if ( len_ds > ON_SQRT_EPSILON*len_dt && len_dt > ON_SQRT_EPSILON*len_ds )
{
ON_3dVector a = ds/len_ds;
ON_3dVector b = dt/len_dt;
normal = ON_CrossProduct( a, b );
rc = normal.Unitize();
}
else
{
// see if we have a singular point
double v[6][3];
int normal_side = side;
ON_BOOL32 bOnSide = false;
ON_Interval sdom = Domain(0);
ON_Interval tdom = Domain(1);
if (s == sdom.Min()) {
normal_side = (normal_side >= 3) ? 4 : 1;
bOnSide = true;
}
else if (s == sdom.Max()) {
normal_side = (normal_side >= 3) ? 3 : 2;
bOnSide = true;
}
if (t == tdom.Min()) {
normal_side = (normal_side == 2 || normal_side == 3) ? 2 : 1;
bOnSide = true;
}
else if (t == tdom.Max()) {
normal_side = (normal_side == 2 || normal_side == 3) ? 3 : 4;
bOnSide = true;
}
if ( !bOnSide )
{
// 2004 November 11 Dale Lear
// Added a retry again with a more generous tolerance
if ( len_ds > ON_EPSILON*len_dt && len_dt > ON_EPSILON*len_ds )
{
ON_3dVector a = ds/len_ds;
ON_3dVector b = dt/len_dt;
normal = ON_CrossProduct( a, b );
rc = normal.Unitize();
}
else
{
rc = false;
}
}
else {
rc = Evaluate( s, t, 2, 3, &v[0][0], normal_side, hint );
if ( rc ) {
rc = ON_EvNormal( normal_side, v[1], v[2], v[3], v[4], v[5], normal);
}
}
}
}
if ( !rc ) {
normal.Zero();
}
return rc;
}
