public static ExpVector NormalAtInPlane(this IEntity self, Exp t, IPlane plane)
{
if (self.plane != null)
{
var tang = self.TangentAt(t);
if (tang == null)
{
return(null);
}
var n = ExpVector.Cross(tang, Vector3.forward);
if (plane == self.plane)
{
return(n);
}
return(plane.DirToFrom(n, self.plane));
}
Param p = new Param("pOn");
var pt = self.PointOn(p);
var result = new ExpVector(pt.x.Deriv(p).Deriv(p), pt.y.Deriv(p).Deriv(p), pt.z.Deriv(p).Deriv(p));
result.x.Substitute(p, t);
result.y.Substitute(p, t);
result.z.Substitute(p, t);
if (plane == null)
{
return(result);
}
return(plane.DirToPlane(result));
}
public static ExpVector TangentAtInPlane(this IEntity entity, Exp t, IPlane plane)
{
if (plane == entity.plane)
{
return(entity.TangentAt(t));
}
return(plane.DirToFrom(entity.TangentAt(t), entity.plane));
}