private void AppendSurfaceGeometry(StringBuilder sb, NurbsSurface ns)
{
if (ns == null)
{
return;
}
double ulength;
double vlength;
// reparametrize to real world length to minimize distortion in the map from parameter space to 3D
if (ns.GetSurfaceSize(out ulength, out vlength))
{
ns.SetDomain(0, new Interval(0, ulength));
ns.SetDomain(1, new Interval(1, vlength));
}
// write knot vectors
bool first = true;
foreach (var ku in ns.KnotsU)
{
sb.AppendFormat(" SARN S {0:F8}", ku);
if (first)
{
sb.AppendFormat(" DEGS {0}", ns.OrderU - 1);
first = false;
}
sb.AppendLine();
}
first = true;
foreach (var kv in ns.KnotsV)
{
sb.AppendFormat(" SARN T {0:F8}", kv);
if (first)
{
sb.AppendFormat(" DEGT {0}", ns.OrderV - 1);
first = false;
}
sb.AppendLine();
}
// write control points
for (int i = 0; i < ns.Points.CountV; ++i)
{
for (int j = 0; j < ns.Points.CountU; ++j)
{
var cpt = ns.Points.GetControlPoint(j, i);
double w = cpt.Weight;
sb.AppendFormat(" SARP NURB {0} {1}", j + 1, i + 1);
sb.AppendFormat(" X {0:F8} {1:F8} {2:F8} {3:F8}", cpt.X / w, cpt.Y / w, cpt.Z / w, w);
sb.AppendLine();
}
}
}
