/*
 * CS5600 University of Utah
 * Charles McGarvey
 * mcgarvey@eng.utah.edu
 */

#ifndef _SPHERE_HH_
#define _SPHERE_HH_

#include "element.hh"


namespace rt {


/*
 * A class for a sphere object.
 */
class sphere : public element
{
    vec_t   origin;
    scal_t  radius;

public:

    sphere(vec_t o, scal_t r = S(1.0)) :
        origin(o), radius(r)
    {}

    virtual ~sphere()
    {}

    virtual bool intersect(ray_t ray, contact_t& hit) const
    {
        vec_t   b = vec_sub(origin, ray.o);
		scal_t  z = vec_dot(b, ray.d);

		// check if the sphere is behind the ray
		if (z < S(0.0)) {
            return false;
        }

		scal_t d2 = vec_dot(b, b) - z * z;
		scal_t r2 = radius * radius;

		// check for an intersection
		if (r2 < d2) {
            return false;
        }

		hit.d = z - std::sqrt(r2 - d2);
		if (hit.d < S(0.0)) {
            return false;
        }

        hit.p = ray_solve(ray, hit.d);
        hit.n = vec_sub(hit.p, origin);
		return true;
    }

    virtual vec_t txcoord(vec_t point) const
    {
        vec_t uv = VEC_ZERO;

        scal_t theta = scal_atan2(point.z, point.x);
        scal_t phi = asin(point.y / radius);

        uv.x = theta / (S(2.0) * M_PI) + S(0.5);
        uv.y = phi / M_PI + S(0.5);

        return uv;
    }
};


/*
 * Destroy a new'd sphere, releasing its memory.
 */
INLINE_MAYBE
void sphere_destroy(sphere* s)
{
    delete s;
}


} // namespace rt

#endif // _SPHERE_HH_