From 4c823f57959a5d821a9f00d8e8c7f57c08ac2ded Mon Sep 17 00:00:00 2001
From: Martin Lehoux <martin@lehoux.net>
Date: Sun, 5 Apr 2020 23:34:05 -0700
Subject: feat - Camera VFOV

---
 camera.go | 14 ++++++++++++++
 main.go   | 37 +++++++++++++++++++++----------------
 utils.go  |  6 ++++++
 3 files changed, 41 insertions(+), 16 deletions(-)

diff --git a/camera.go b/camera.go
index 6cc3391..2992b02 100644
--- a/camera.go
+++ b/camera.go
@@ -1,11 +1,25 @@
 package main
 
+import "math"
+
 // Camera handle view position and screen
 type Camera struct {
 	lowerLeftCorner              Vec3D
 	origin, horizontal, vertical Vec3D
 }
 
+// NewCamera creates a new camera
+func NewCamera(vfov float64, aspect float64) Camera {
+	origin := Vec3D{0.0, 0.0, 0.0}
+	theta := DegreesToRadians(vfov)
+	halfHeight := math.Tan(theta / 2.0)
+	halfWidth := aspect * halfHeight
+	lowerLeftCorner := Vec3D{-halfWidth, -halfHeight, -1.0}
+	horizontal := Vec3D{2.0 * halfWidth, 0.0, 0.0}
+	vertical := Vec3D{0.0, 2.0 * halfHeight, 0.0}
+	return Camera{lowerLeftCorner, origin, horizontal, vertical}
+}
+
 // GetRay computes Ray given screen params
 func (camera Camera) GetRay(u float64, v float64) Ray {
 	return Ray{
diff --git a/main.go b/main.go
index 7042d21..957fc92 100644
--- a/main.go
+++ b/main.go
@@ -2,6 +2,7 @@
 package main
 
 import (
+	"math"
 	"math/rand"
 
 	"github.com/schollz/progressbar"
@@ -26,24 +27,28 @@ const (
 
 func main() {
 	// Scene
-	lowerLeftCorner := Vec3D{-2.0, -1.0, -1.0}
-	origin := Vec3D{0.0, 0.0, 0.0}
-	horizontal := Vec3D{4.0, 0.0, 0.0}
-	vertical := Vec3D{0.0, 2.0, 0.0}
-	camera := Camera{lowerLeftCorner, origin, horizontal, vertical}
+	camera := NewCamera(90.0, float64(Width)/float64(Height))
 
-	matRed := Lambertian{Color{0.7, 0.3, 0.3}}
-	matGreen := Lambertian{Color{0.8, 0.8, 0.0}}
-	metalGrey := Metal{Color{0.8, 0.8, 0.8}, 0.3}
+	r := math.Cos(math.Pi / 4)
+	blue := Lambertian{Color{0.0, 0.0, 1.0}}
+	red := Lambertian{Color{1.0, 0.0, 0.0}}
+	World := HitableList{
+		Sphere{Vec3D{-r, 0.0, -1.0}, r, blue},
+		Sphere{Vec3D{r, 0.0, -1.0}, r, red},
+	}
+
+	// matRed := Lambertian{Color{0.7, 0.3, 0.3}}
+	// matGreen := Lambertian{Color{0.8, 0.8, 0.0}}
+	// metalGrey := Metal{Color{0.8, 0.8, 0.8}, 0.3}
 	// metalBrown := Metal{Color{0.8, 0.6, 0.2}, 1.0}
-	glass := Dielectric{1.5}
+	// glass := Dielectric{1.5}
 
-	WORLD := HitableList{
-		Sphere{Vec3D{0.0, 0.0, -1.0}, 0.5, glass},
-		Sphere{Vec3D{-1.0, 0.0, -1.0}, 0.5, metalGrey},
-		Sphere{Vec3D{1.0, 0.0, -1.0}, 0.5, matRed},
-		Sphere{Vec3D{0.0, -100.5, -1.0}, 100.0, matGreen},
-	}
+	// World := HitableList{
+	// 	Sphere{Vec3D{0.0, 0.0, -1.0}, 0.5, glass},
+	// 	Sphere{Vec3D{-1.0, 0.0, -1.0}, 0.5, metalGrey},
+	// 	Sphere{Vec3D{1.0, 0.0, -1.0}, 0.5, matRed},
+	// 	Sphere{Vec3D{0.0, -100.5, -1.0}, 100.0, matGreen},
+	// }
 
 	// Program
 	// start := AddVec3D(Origin, Vec3D{-1.0, 0.0, 0.0})
@@ -61,7 +66,7 @@ func main() {
 				u := (float64(y) + rand.Float64()) / float64(Width)
 				v := (float64(x) + rand.Float64()) / float64(Height)
 				ray := camera.GetRay(u, v)
-				colorList[it] = RayColor(ray, WORLD, 0)
+				colorList[it] = RayColor(ray, World, 0)
 			}
 			color := ColorMeanSquare(colorList)
 			frame[Height-1-x][y] = color.ToPixel()
diff --git a/utils.go b/utils.go
index ca40e87..a0d0e7c 100644
--- a/utils.go
+++ b/utils.go
@@ -1,5 +1,7 @@
 package main
 
+import "math"
+
 // FMin return mins of floats
 func FMin(a float64, b float64) float64 {
 	if a >= b {
@@ -7,3 +9,7 @@ func FMin(a float64, b float64) float64 {
 	}
 	return b
 }
+
+func DegreesToRadians(degrees float64) float64 {
+	return degrees * 2.0 * math.Pi / 360.0
+}
-- 
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