Using this:
#include
#include <iostream>
int main()
{
namespace bg = boost::geometry; // bg = 'B'oost 'G'eometry
namespace cs = bg::cs; // cs = 'C'oordinate 'S'ystem
typedef bg::model::point CartesianType;
CartesianType cartesian(-6.89, -1.61, -1.64);
// (theta, phi)
typedef bg::model::pointbg::degree >
SphericalType;
SphericalType spherical;
bg::strategy::transform::from_cartesian_3_to_spherical_equatorial_2 strategy;
bg::transform(cartesian, spherical, strategy);
std::cout
<< "cartesian: " << bg::dsv(cartesian) << std::endl
<< "spherical: " << bg::dsv(spherical) << std::endl;
return 0;
}
I am getting the second coordinate of 'spherical' equal to 'nan'. I
stepped through the Boost code, and got to this in
strategy_transform.hpp:
template
inline bool cartesian_to_spherical_equatorial2(T x, T y, T z, P& p)
{
assert_dimension();
set_from_radian<0>(p, atan2(y, x));
set_from_radian<1>(p, asin(z));
return true;
}
Here you see asin(z) . asin() requires the argument to be [-1,1]
(http://www.cplusplus.com/reference/clibrary/cmath/asin/). However,
this should just be the z component of any Cartesian point right? Is
there some restriction on the input Cartesian point to
cartesian_to_spherical_equatorial2 (and hence the
from_cartesian_3_to_spherical_equatorial_2 strategy)?
I see a restriction on from_cartesian_3_to_spherical_polar_2:
\note If x,y,z point is not lying on unit sphere, transformation will
return false
but I don't see the same restriction on
from_cartesian_3_to_spherical_equatorial_2. Additionally, it doesn't
seem to just be a missing comment because the transform() call
actually returns true even though this point is not on the unit
sphere. If I normalize the point and call the function:
CartesianType cartesian(-0.94862, -0.22167, -0.22580);
The conversion seems to work successfully, and the call still returns true.
Any thoughts? Is this a bug? If not, why is the function not returning
false? And better, shouldn't this condition have at least an assertion
(i.e. if the norm != 1, then return false or throw)?
Thanks,
David
