From cc772aa6f9d3dd849a254c6743167cd7e6a3cdf5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bor=20Gro=C5=A1elj=20Simi=C4=87?=
 <bor.groseljsimic@telemach.net>
Date: Tue, 11 Jan 2022 00:16:07 +0100
Subject: [PATCH] dielectric materials

---
 main.ha     |  4 ++--
 material.ha | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 54 insertions(+), 3 deletions(-)

diff --git a/main.ha b/main.ha
index 640d564..0c49125 100644
--- a/main.ha
+++ b/main.ha
@@ -5,8 +5,8 @@ use time;
 
 fn init_scene() *hittable = {
 	let ground = alloc(make_lambertian(&C(0.8, 0.8, 0.0)));
-	let center = alloc(make_lambertian(&C(0.7, 0.3, 0.3)));
-	let left = alloc(make_metal(&C(0.8, 0.8, 0.8), 0.3));
+	let center = alloc(make_dielectric(1.5));
+	let left = alloc(make_dielectric(1.2));
 	let right = alloc(make_metal(&C(0.8, 0.6, 0.2), 1.0));
 	let a = alloc(multi([]));
 	append(a.arr, [
diff --git a/material.ha b/material.ha
index e9cf3c0..78b544d 100644
--- a/material.ha
+++ b/material.ha
@@ -1,4 +1,4 @@
-use math::{absf64};
+use math::{absf64, powf64, sqrtf64};
 
 export type scatterfunc = *fn(
 	mat: *const material,
@@ -73,3 +73,54 @@ fn metal_scatter(
 	*att = m.albedo;
 	return dot(r_out.direction, rec.normal) > 0.0;
 };
+
+fn refract(v: *const vector, n: *const vector, r: f64) vector = {
+	let k = dot(neg(*v), *n);
+	let k = if (k < 1.0) k else 1.0;
+	let c1 = scale(sum(*v, scale(*n, k)), r);
+	let c2 = scale(*n, -sqrtf64(absf64(1.0 - dot(c1, c1))));
+	return sum(c1, c2);
+};
+
+fn schlick_reflectance(cos: f64, r_ind: f64) f64 = {
+	let r0 = (1.0 - r_ind) / (1.0 + r_ind);
+	r0 = r0 * r0;
+	return r0 + (1.0 - r0) * powf64(1.0 - cos, 5.0);
+};
+
+type dielectric = struct {
+	material,
+	r_ind: f64,
+};
+
+fn make_dielectric(r: f64) dielectric = dielectric {
+	scatter = &dielectric_scatter,
+	r_ind = r,
+};
+
+fn dielectric_scatter(
+	m: *const material,
+	r_in: *const ray,
+	rec: *const hit_record,
+	att: *color,
+	r_out: *ray
+) bool = {
+	let d = m: *const dielectric;
+	*att = C(1.0, 1.0, 1.0);
+
+	let r_ind = if (rec.front_face) 1.0 / d.r_ind else d.r_ind;
+	let unit_dir = unit(r_in.direction);
+	let cos = dot(neg(unit_dir), rec.normal);
+	let cos = if (cos < 1.0) cos else 1.0;
+	let sin = sqrtf64(1.0 - cos * cos);
+	*r_out = ray {
+		origin = rec.point,
+		direction =
+			if (r_ind * sin <= 1.0
+			|| schlick_reflectance(cos, r_ind) > random(0.0, 1.0))
+				refract(&unit_dir, &rec.normal, r_ind)
+			else
+				reflect(&unit_dir, &rec.normal),
+	};
+	return true;
+};
-- 
2.45.2