Add material support

material.hpp

@@ -0,0 +1,52 @@
+#ifndef MATERIAL_H
+#define MATERIAL_H
+
+#include "rtweekend.hpp"
+
+struct material {
+    virtual bool scatter(const ray& r_in, const hit_record& rec, color& attenuation, ray& scattered) const = 0;
+};
+
+struct lambertian : material {
+    /* Attributes */
+    color albedo;
+    // Constructor
+    lambertian(const color& c) { albedo = c; }
+
+    #pragma GCC diagnostic push
+    #pragma GCC diagnostic ignored "-Wunused-parameter"
+    virtual bool scatter(const ray& r_in, const hit_record& rec, color& attenuation, ray& scattered) const override
+    {
+        vec3 scatter_direction = rec.normal + random_unit_vector();
+
+        /* NOTE: it is possible that the random vector we generate is exactly opposite to the normal vector,
+           in which case it will sum to a near-zero scatter vector and generate degenerate results.
+           We check for near-zero vectors here.
+         */
+
+        if (scatter_direction.near_zero())
+            scatter_direction = rec.normal;         
+        
+        scattered = ray(rec.p, scatter_direction);
+        attenuation = albedo;
+        return true;
+    }
+    #pragma GCC diagnostic pop
+};
+
+struct metal : material {
+    /* Attributes */
+    color albedo;
+    // Constructor
+    metal(const color& c) { albedo = c; };
+
+    virtual bool scatter(const ray& r_in, const hit_record& rec, color& attenuation, ray& scattered) const override
+    {
+        vec3 reflected = reflect(normalize(r_in.direction), rec.normal);
+        scattered = ray(rec.p, reflected);
+        attenuation = albedo;
+        return (dot(scattered.direction, rec.normal) > 0);
+    }
+};
+
+#endif