Materials and metals

main.go

@@ -74,6 +74,11 @@ func (v Vec3) Length_squared() float32 {
 	return v.E[0]*v.E[0] + v.E[1]*v.E[1] + v.E[2]*v.E[2]
 }
 
+func (v Vec3) Near_zero() bool {
+	var s float64 = 1e-8
+	return (math.Abs(float64(v.E[0])) < s && math.Abs(float64(v.E[1])) < s && math.Abs(float64(v.E[2])) < s)
+}
+
 // Vector utility functions
 
 func (v Vec3) String() string {
@@ -141,6 +146,10 @@ func RandomOnHemisphere(normal Vec3) Vec3 {
 	}
 }
 
+func Reflect(v Vec3, n Vec3) Vec3 {
+	return v.Sub(n.Mult(2*Dot(v,n)))
+}
+
 const pi float32 = 3.1415926535897932385
 
 func Degrees_to_radians(degrees float32) float32 {
@@ -270,6 +279,7 @@ type Hit_record struct {
 	normal Vec3
 	t float32
 	front_face bool
+	mat Material
 }
 
 func (rec *Hit_record) Set_face_normal(r *Ray, outward_normal Vec3) {
@@ -288,6 +298,7 @@ func (rec *Hit_record) Set_face_normal(r *Ray, outward_normal Vec3) {
 type Sphere struct {
 	center Vec3
 	radius float32
+	mat Material
 }
 
 func (s Sphere) Hit_sphere(r *Ray, ray_t *Interval, rec *Hit_record) bool {
@@ -314,6 +325,7 @@ func (s Sphere) Hit_sphere(r *Ray, ray_t *Interval, rec *Hit_record) bool {
 	rec.p = r.At(rec.t)
 	outward_normal := rec.p.Sub(s.center).Div(s.radius)
 	rec.Set_face_normal(r, outward_normal)
+	rec.mat = s.mat
 	return true
 }
 
@@ -349,6 +361,55 @@ func (hl Hittable) Hit(r *Ray, ray_t Interval, rec *Hit_record) bool {
 	return hit_anything
 }
 
+// =============== MATERIAL =================
+type Material struct {
+	lambertian bool
+	metal bool
+	albedo Vec3
+	fuzz float32
+}
+
+func NewMaterial(l bool, m bool, a Vec3, f float32) Material {
+	if f >= 1.0 {
+		return Material{
+			lambertian: l,
+			metal: m,
+			albedo : a,
+			fuzz: 1.0,
+		}
+	} else {
+		return Material{
+			lambertian: l,
+			metal: m,
+			albedo : a,
+			fuzz: f,
+		}
+	}
+
+}
+
+func (mat Material) Scatter(r_in *Ray, rec *Hit_record, attenuation *Vec3, scattered *Ray) bool {
+	if (mat.lambertian) {	
+		scatter_direction := rec.normal.Add(RandomUnitVector())
+		// Catch degenerate scatter direction
+		if scatter_direction.Near_zero() {
+			scatter_direction = rec.normal
+		}
+
+		*scattered = *NewRay(rec.p, scatter_direction)
+		*attenuation = mat.albedo
+	} else if (mat.metal) {
+		var reflected Vec3 = Reflect(Unit_vector(r_in.Direction()), rec.normal)
+		*scattered = *NewRay(rec.p, reflected.Add(RandomUnitVector().Mult(mat.fuzz)))
+		*attenuation = mat.albedo
+		if !(Dot(scattered.Direction(), rec.normal) > 0) {
+			return false
+		}
+	}
+	return true
+}
+
+
 // =============== CAMERA ===================
 
 type Camera struct {
@@ -374,9 +435,12 @@ func Ray_color(r Ray, depth int, world *Hittable) Vec3 {
 		return NewColor(0,0,0)
 	}
 	if (world.Hit(&r, *NewInterval(0.001, float32(math.Inf(1))), &rec)) {
-		//direction := RandomOnHemisphere(rec.normal)
-		direction := rec.normal.Add(RandomUnitVector())
-		return Ray_color(*((NewRay(rec.p, direction))), depth-1, world).Mult(0.5)
+		var scattered Ray
+		var attenuation Vec3
+		if ((rec.mat).Scatter(&r, &rec, &attenuation, &scattered)) {
+			return attenuation.MultVec(Ray_color(scattered, depth-1, world))
+		}
+		return NewColor(0.0,0.0,0.0)
 	}
 	unit_direction := Unit_vector(r.Direction())
 	a := (unit_direction.Y() + 1.0)*0.5
@@ -447,16 +511,34 @@ func (cam *Camera) Pixel_sample_square() Vec3 {
 
 // =============== MAIN =====================
 func main() {
+	// Materials
+	material_ground := NewMaterial(true, false, NewColor(0.8, 0.8, 0.0), 0.0)
+	material_center := NewMaterial(true, false, NewColor(0.7, 0.3, 0.3), 0.0)
+	material_left := NewMaterial(false, true, NewColor(0.8, 0.8, 0.8), 0.3)
+	material_right := NewMaterial(false, true, NewColor(0.8, 0.6, 0.2), 1.0)
+
 	// World
 
 	world := NewHittable()
-	world.Add(Sphere{
-		center: NewVec3(0, 0, -1),
-		radius: 0.5,
-	})
 	world.Add(Sphere{
 		center: NewVec3(0, -100.5, -1),
 		radius: 100,
+		mat: material_ground,
+	})
+	world.Add(Sphere{
+		center: NewVec3(0, 0, -1.0),
+		radius: 0.5,
+		mat: material_center,
+	})
+	world.Add(Sphere{
+		center: NewVec3(-1.0, 0, -1.0),
+		radius: 0.5,
+		mat: material_left,
+	})
+	world.Add(Sphere{
+		center: NewVec3(1.0, 0, -1.0),
+		radius: 0.5,
+		mat: material_right,
 	})
 	// Image