From 8730659596dbfdb9625c0fc413625b261f7d6d70 Mon Sep 17 00:00:00 2001
From: Martin Lehoux <martin@lehoux.net>
Date: Sat, 4 Apr 2020 19:55:48 -0700
Subject: feat - Add Metal material

---
 main.go     | 13 +++++++++----
 material.go | 11 +++++++++++
 vec3d.go    |  4 ++++
 3 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/main.go b/main.go
index b8f6335..316ebff 100644
--- a/main.go
+++ b/main.go
@@ -1,3 +1,4 @@
+// TODO Use pointers when needed to reduce memory
 package main
 
 import (
@@ -22,11 +23,15 @@ func main() {
 
 	MAT_RED := Lambertian{Color{0.7, 0.3, 0.3}}
 	MAT_GREEN := Lambertian{Color{0.8, 0.8, 0.0}}
+	METAL_GREY := Metal{Color{0.8, 0.8, 0.8}, 0.3}
+	METAL_BROWN := Metal{Color{0.8, 0.6, 0.2}, 1.0}
 
-	SPHERE := Sphere{Vec3D{0.0, 0.0, -1.0}, 0.5, MAT_RED}
-	EARTH := Sphere{Vec3D{0.0, -100.5, -1.0}, 100.0, MAT_GREEN}
-
-	WORLD := HitableList{EARTH, SPHERE}
+	WORLD := HitableList{
+		Sphere{Vec3D{0.0, 0.0, -1.0}, 0.5, MAT_RED},
+		Sphere{Vec3D{-1.0, 0.0, -1.0}, 0.5, METAL_GREY},
+		Sphere{Vec3D{1.0, 0.0, -1.0}, 0.5, METAL_BROWN},
+		Sphere{Vec3D{0.0, -100.5, -1.0}, 100.0, MAT_GREEN},
+	}
 	frame := Frame{}
 	bar := progressbar.New(HEIGHT)
 	for x := 0; x < HEIGHT; x++ {
diff --git a/material.go b/material.go
index db1e4d6..a36fb52 100644
--- a/material.go
+++ b/material.go
@@ -14,3 +14,14 @@ func (lambertian Lambertian) Scatter(ray Ray, hit HitRecord) (Ray, Color) {
 	scattered := Ray{hit.point, direction}
 	return scattered, lambertian.albedo
 }
+
+type Metal struct {
+	albedo Color
+	fuzz   float64
+}
+
+func (metal Metal) Scatter(ray Ray, hit HitRecord) (Ray, Color) {
+	reflected := AddVec3D(ray.direction.Unit().Reflect(hit.normal), ScalarProduct(metal.fuzz, RandomInUnitSphere()))
+	scattered := Ray{hit.point, reflected}
+	return scattered, metal.albedo
+}
diff --git a/vec3d.go b/vec3d.go
index fcf5b1c..9e4ced0 100644
--- a/vec3d.go
+++ b/vec3d.go
@@ -25,6 +25,10 @@ func (vec Vec3D) Unit() Vec3D {
 	return ScalarProduct(1.0/length, vec)
 }
 
+func (vec Vec3D) Reflect(normal Vec3D) Vec3D {
+	return SubVec3D(vec, ScalarProduct(2*DotProduct(vec, normal), normal))
+}
+
 func AddVec3D(vec1 Vec3D, vec2 Vec3D) Vec3D {
 	return Vec3D{vec1.x + vec2.x, vec1.y + vec2.y, vec1.z + vec2.z}
 }
-- 
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