1 files changed, 32 insertions, 0 deletions
diff --git a/src/dielectric.cpp b/src/dielectric.cpp
new file mode 100644
index 0000000..80ca069
--- /dev/null
+++ b/src/dielectric.cpp
@@ -0,0 +1,32 @@
+#include "dielectric.hpp"
+#include "rt.hpp"
+#include "hittable.hpp"
+
+dielectric::dielectric(double index_of_refraction)
+    : ior(index_of_refraction) {}
+
+bool dielectric::scatter(const ray& r, const struct hit_info& info, color& attenuation, ray& scattered) const {
+    auto unit_direction = r.direction.unit();
+    auto refraction_ratio = info.front_face ? (1.0 / ior) : ior;
+    double cos_theta = fmin(info.normal.dot(-unit_direction), 1.0);
+    double sin_theta = sqrt(1.0 - cos_theta * cos_theta);
+
+    vec3 direction;
+    if (refraction_ratio * sin_theta > 1.0 || reflectance(cos_theta, refraction_ratio) > randd()) {
+        direction = reflect(unit_direction, info.normal);
+    } else {
+        direction = refract(unit_direction, info.normal, refraction_ratio);
+    }
+
+    scattered = ray { info.point, direction };
+    attenuation = { 1.0, 1.0, 1.0 };
+
+    return true;
+}
+
+double dielectric::reflectance(double cosine, double ref_idx) {
+    // Use Schlick's approximation for reflectance.
+    auto r0 = (1 - ref_idx) / (1 + ref_idx);
+    r0 = r0 * r0;
+    return r0 + (1 - r0) * pow ((1 - cosine), 5);
+}