removed extinction coefficient

src/dielectric.hpp

@@ -5,7 +5,7 @@
 
 class dielectric: public material{
 public:
-  dielectric(double index_of_refraction_inside, double index_of_refraction_outside, double extinction_inside = 0.);
+  dielectric(double index_of_refraction_inside, double index_of_refraction_outside);
 
   virtual bool scatter(
     const ray& r_in, const hit_record& rec,
@@ -19,7 +19,6 @@ private:
 
   double ir_inside; //index of refraction inside material
   double ir_outside; //index of refraction outside material
-  double extinction_inside; //exponential extinction coefficient inside material
 };
 
 #endif