include/crbn/basic/bsphere.hpp

#ifndef __bounding_sphere_hpp__
#define __bounding_sphere_hpp__

#include <crbn/basic/vec3.hpp>
#include <crbn/basic/mat4.hpp>

// Bounding sphere
struct bsphere{
  vec3  center;
  float radius;

  bsphere() : center(0.0, 0.0 , 0.0), radius(0.0) {}
  bsphere(const vec3& c, const float& r) : center(c), radius(r) {}
  bsphere(const bsphere& b) : center(b.center), radius(b.radius) {}
};

// v in b ?
inline bool inside( bsphere& b, vec3& v ) {
  return (vdistance(v, b.center) <= b.radius);
}

// a = b U c
inline void merge( bsphere& a, bsphere& b, bsphere& c ) {
  float bc = vdistance(b.center, c.center);
  a.radius = 0.5 * (b.radius + c.radius + bc);

  vsub(a.center, c.center, b.center);
  vmul(a.center, (c.radius - b.radius) / bc);
  vadd(a.center, c.center);
  vadd(a.center, c.center);
  vmul(a.center, 0.5);
}

// a = a U b
inline void merge( bsphere& a, bsphere& b ) {
  bsphere c(a);
  merge(a, b, c);
}

// a = b * m
inline void transform( bsphere& a, bsphere& b, mat4& m ) {
  // Create a north pole point  
  vec3 v;
  vec3 pole(b.center);
  pole.z += b.radius;

  // Tranform pole and center
  // mmulp(pole, m, vec3(b.center.x, b.center.y, b.center.z + b.radius);
  mmulp( v, m, pole); 
  mmulp( a.center, m, b.center);
  
  // Compute new radius
  a.radius = vdistance(v, a.center);
}

// Are the two sphere overlapping?
inline bool overlap( bsphere& a, bsphere& b ) {
  return (vdistance(a.center, b.center) <= (a.radius + b.radius));
}

#endif // __bounding_sphere_hpp__

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