text: //==================================================================================================
  // Written in 2016 by Peter Shirley <ptrshrl@gmail.com>
  //
  // To the extent possible under law, the author(s) have dedicated all copyright and related and
  // neighboring rights to this software to the public domain worldwide. This software is distributed
  // without any warranty.
  //
  // You should have received a copy (see file COPYING.txt) of the CC0 Public Domain Dedication along
  // with this software. If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
  //==================================================================================================
  // Portado para GPU por Luciano Soares <lpsoares@gmail.com>
  
  #ifndef VEC3H
  #define VEC3H
  
  #include <math.h>
  #include <stdlib.h>
  #include <iostream>
  
  class vec3  {
  
      
  public:
      __device__ __host__ vec3() {}
      __device__ __host__ vec3(float e0, float e1, float e2) { e[0] = e0; e[1] = e1; e[2] = e2; }
      __device__ __host__ inline float x() const { return e[0]; }
      __device__ __host__ inline float y() const { return e[1]; }
      __device__ __host__ inline float z() const { return e[2]; }
      __device__ __host__ inline float r() const { return e[0]; }
      __device__ __host__ inline float g() const { return e[1]; }
      __device__ __host__ inline float b() const { return e[2]; }
      
      __device__ __host__ inline const vec3& operator+() const { return *this; }
      __device__ __host__ inline vec3 operator-() const { return vec3(-e[0], -e[1], -e[2]); }
      __device__ __host__ inline float operator[](int i) const { return e[i]; }
      __device__ __host__ inline float& operator[](int i) { return e[i]; };
      
      __device__ __host__ inline vec3& operator+=(const vec3 &v2);
      __device__ __host__ inline vec3& operator-=(const vec3 &v2);
      __device__ __host__ inline vec3& operator*=(const vec3 &v2);
      __device__ __host__ inline vec3& operator/=(const vec3 &v2);
      __device__ __host__ inline vec3& operator*=(const float t);
      __device__ __host__ inline vec3& operator/=(const float t);
      
      __device__ __host__ inline float length() const { return sqrt(e[0]*e[0] + e[1]*e[1] + e[2]*e[2]); }
  
      __device__ inline float length_gpu() const { return sqrt(e[0]*e[0] + e[1]*e[1] + e[2]*e[2]); }
  
  
      __device__ __host__ inline float squared_length() const { return e[0]*e[0] + e[1]*e[1] + e[2]*e[2]; }
      __device__ __host__ inline void make_unit_vector();
      
      float e[3];
  };
  
  
  
  __host__ inline std::istream& operator>>(std::istream &is, vec3 &t) {
      is >> t.e[0] >> t.e[1] >> t.e[2];
      return is;
  }
  
  __host__ inline std::ostream& operator<<(std::ostream &os, const vec3 &t) {
      os << t.e[0] << " " << t.e[1] << " " << t.e[2];
      return os;
  }
  
  __device__ __host__ inline void vec3::make_unit_vector() {
      float k = ((float)1.0) / sqrt(e[0]*e[0] + e[1]*e[1] + e[2]*e[2]);
      e[0] *= k; e[1] *= k; e[2] *= k;
  }
  
  __device__ __host__ inline vec3 operator+(const vec3 &v1, const vec3 &v2) {
      return vec3(v1.e[0] + v2.e[0], v1.e[1] + v2.e[1], v1.e[2] + v2.e[2]);
  }
  
  __device__ __host__ inline vec3 operator-(const vec3 &v1, const vec3 &v2) {
      return vec3(v1.e[0] - v2.e[0], v1.e[1] - v2.e[1], v1.e[2] - v2.e[2]);
  }
  
  __device__ __host__ inline vec3 operator*(const vec3 &v1, const vec3 &v2) {
      return vec3(v1.e[0] * v2.e[0], v1.e[1] * v2.e[1], v1.e[2] * v2.e[2]);
  }
  
  __device__ __host__ inline vec3 operator/(const vec3 &v1, const vec3 &v2) {
      return vec3(v1.e[0] / v2.e[0], v1.e[1] / v2.e[1], v1.e[2] / v2.e[2]);
  }
  
  __device__ __host__ inline vec3 operator*(float t, const vec3 &v) {
      return vec3(t*v.e[0], t*v.e[1], t*v.e[2]);
  }
  
  __device__ __host__ inline vec3 operator/(vec3 v, float t) {
      return vec3(v.e[0]/t, v.e[1]/t, v.e[2]/t);
  }
  
  __device__ __host__ inline vec3 operator*(const vec3 &v, float t) {
      return vec3(t*v.e[0], t*v.e[1], t*v.e[2]);
  }
  
  __device__ __host__ inline float dot(const vec3 &v1, const vec3 &v2) {
      return v1.e[0] *v2.e[0] + v1.e[1] *v2.e[1]  + v1.e[2] *v2.e[2];
  }
  
  __device__ __host__ inline vec3 cross(const vec3 &v1, const vec3 &v2) {
      return vec3( (v1.e[1]*v2.e[2] - v1.e[2]*v2.e[1]),
                  (-(v1.e[0]*v2.e[2] - v1.e[2]*v2.e[0])),
                  (v1.e[0]*v2.e[1] - v1.e[1]*v2.e[0]));
  }
  
  
  __device__ __host__ inline vec3& vec3::operator+=(const vec3 &v){
      e[0]  += v.e[0];
      e[1]  += v.e[1];
      e[2]  += v.e[2];
      return *this;
  }
  
  __device__ __host__ inline vec3& vec3::operator*=(const vec3 &v){
      e[0]  *= v.e[0];
      e[1]  *= v.e[1];
      e[2]  *= v.e[2];
      return *this;
  }
  
  __device__ __host__ inline vec3& vec3::operator/=(const vec3 &v){
      e[0]  /= v.e[0];
      e[1]  /= v.e[1];
      e[2]  /= v.e[2];
      return *this;
  }
  
  __device__ __host__ inline vec3& vec3::operator-=(const vec3& v) {
      e[0]  -= v.e[0];
      e[1]  -= v.e[1];
      e[2]  -= v.e[2];
      return *this;
  }
  
  __device__ __host__ inline vec3& vec3::operator*=(const float t) {
      e[0]  *= t;
      e[1]  *= t;
      e[2]  *= t;
      return *this;
  }
  
  __device__ __host__ inline vec3& vec3::operator/=(const float t) {
      float k = ((float)1.0)/t;
      
      e[0]  *= k;
      e[1]  *= k;
      e[2]  *= k;
      return *this;
  }
  
  __device__ __host__ inline vec3 unit_vector(vec3 v) {
      return v / v.length();
  }
  
  #endif
  