Chapter 8 done

main.go

@@ -3,7 +3,14 @@ package main
 import "fmt" // for IO and standard library
 import "os" // for handling the progress bar
 import "math" // for maths
-import "unsafe"
+import "unsafe" // for fast inverse square pointers
+import "math/rand" // for random
+import "time" // for random
+
+
+func init() {
+    rand.Seed(time.Now().UnixNano())
+}
 
 // ================ VEC3 CLASS =====================
 
@@ -117,10 +124,28 @@ func Degrees_to_radians(degrees float32) float32 {
 	return (degrees * pi) / 180.0
 }
 
+func RandomDouble() float32 {
+    // Returns a random real in [0,1).
+    return rand.Float32()
+}
+
+func RandomDoubleInRange(min, max float32) float32 {
+    // Returns a random real in [min,max).
+    return min + (max-min)*RandomDouble()
+}
+
 // ============== COLOUR CLASS ==============
 
-func Write_color(v Vec3) {
-	fmt.Println(int(255.999*v.E[0]), int(255.999*v.E[1]), int(255.999*v.E[2]))
+func Write_color(v Vec3, samples_per_pixel int) {
+	// Averaging
+
+	r := v.X() / float32(samples_per_pixel)
+	g := v.Y() / float32(samples_per_pixel)
+	b := v.Z() / float32(samples_per_pixel)
+
+	// Write the translate [0, 255] value of each color component
+	intensity := NewInterval(0.000, 0.999)
+	fmt.Println(int(intensity.Clamp(r)* 256.0), int(intensity.Clamp(g)* 256.0), int(intensity.Clamp(b)* 256.0))
 }
 
 func NewColor(e0, e1, e2 float32) Vec3 {
@@ -187,6 +212,15 @@ func (i *Interval) Surrounds(x float32) bool {
 	return i.min < x && x < i.max
 }
 
+func (i *Interval) Clamp(x float32) float32 {
+	if (x < i.min) {
+		return i.min
+	} else if (x > i.max) {
+		return i.max
+	}
+	return x
+}
+
 var Empty *Interval = NewInterval()
 var Universe *Interval = NewInterval(float32(math.Inf(-1)), float32(math.Inf(1)))
 
@@ -287,13 +321,14 @@ type Camera struct {
 	pixel00_loc Vec3
 	pixel_delta_u Vec3
 	pixel_delta_v Vec3
+	samples_per_pixel int
 } 
 
 func NewCamera() *Camera {
 	return &Camera{}
 }
 
-func  Ray_color(r Ray, world *Hittable) Vec3 {
+func Ray_color(r Ray, world *Hittable) Vec3 {
 	var rec Hit_record
 	if (world.Hit(&r, *NewInterval(0, float32(math.Inf(1))), &rec)) {
 		return rec.normal.Add(NewColor(1,1,1)).Mult(0.5)
@@ -337,16 +372,32 @@ func (cam *Camera) Render(world *Hittable) {
     for j := 0; j < cam.image_height; j++ {
         fmt.Fprintf(os.Stderr, "\rScanlines remaining: %d ", cam.image_height-j)
         for i := 0; i < cam.image_width; i++ {
-            pixel_center := cam.pixel00_loc.Add(cam.pixel_delta_u.Mult(float32(i))).Add(cam.pixel_delta_v.Mult(float32(j)))
-            ray_direction := pixel_center.Sub(cam.center)
-            r := NewRay(cam.center, ray_direction)
-
-            pixel_color := Ray_color(*r, world)
-            Write_color(pixel_color)
+			pixel_color := NewColor(0,0,0)
+			for sample := 0; sample < cam.samples_per_pixel; sample++ {
+				r := cam.GetRay(i, j)
+				pixel_color = pixel_color.Add(Ray_color(*r, world))
+			}
+			Write_color(pixel_color, cam.samples_per_pixel)
         }
     }
 }
 
+func (cam *Camera) GetRay(i, j int) *Ray {
+	// Get a randomly sampled camera ray for the pixel at location i,j
+	pixel_center := cam.pixel00_loc.Add(cam.pixel_delta_u.Mult(float32(i))).Add(cam.pixel_delta_v.Mult(float32(j)))
+	pixel_sample := pixel_center.Add(cam.Pixel_sample_square())
+
+	ray_direction := pixel_sample.Sub(cam.center)
+	return NewRay(cam.center, ray_direction)
+}
+
+func (cam *Camera) Pixel_sample_square() Vec3 {
+	// Returns a random point in the square surrounding a pixel at the origin
+	px := -0.5 + RandomDouble()
+	py := -0.5 + RandomDouble()
+	return (cam.pixel_delta_u.Mult(px).Add(cam.pixel_delta_v.Mult(py)))
+}
+
 
 
 // =============== MAIN =====================
@@ -367,7 +418,7 @@ func main() {
 	cam := NewCamera()
 	cam.aspect_ratio = 16.0 / 9.0
     cam.image_width = 400
-	 
+	cam.samples_per_pixel = 100
 	cam.Render(world)
 	// INFO: The pixels are written out in rows.
 	// Image file can be created with