Parametric Butterfly Pillow

ButterflyPillow.cpp

class ParametricButterflyPillow
{
  public:
    explicit ParametricButterflyPillow(const double radius) {}

    GVector3 evaluate(const double u, const double v) const
    {
      const double theta = 2.0 * Pi * u;
      const double phi = Pi * v;
      return GVector3(
        cos(theta) * sin(phi),
        sin(theta) * cos(phi),
        cos(phi)
      );
    }

    GVector3 evaluate_normal(const double u, const double v) const		 +    const double m_radius;
    {
      GVector3 normal = evaluate(u, v);		
      return normalize(normal);		
    }
  };