From f2ade1eee29f71195f4f921bc50bc6894e8efb57 Mon Sep 17 00:00:00 2001
From: Bill Thiede <git@xinu.tv>
Date: Sat, 13 Aug 2022 20:35:15 -0700
Subject: [PATCH] zigrtiow: partially configurable camera.

---
 zigrtiow/src/camera.zig | 21 ++++++++++++++++++---
 zigrtiow/src/main.zig   | 19 +++++++++----------
 2 files changed, 27 insertions(+), 13 deletions(-)

diff --git a/zigrtiow/src/camera.zig b/zigrtiow/src/camera.zig
index f7d2170..fce465b 100644
--- a/zigrtiow/src/camera.zig
+++ b/zigrtiow/src/camera.zig
@@ -1,9 +1,19 @@
 const vec = @import("./vec.zig");
+const std = @import("std");
 
 const Ray = @import("./ray.zig").Ray;
 
 const Point3 = vec.Point3;
 const Vec3 = vec.Vec3;
+const math = std.math;
+const pi = math.pi;
+const tan = math.tan;
+
+// Utility Functions
+
+fn degrees_to_radians(degrees: f32) f32 {
+    return degrees * pi / 180.0;
+}
 
 pub const Camera = struct {
     origin: Point3,
@@ -11,10 +21,15 @@ pub const Camera = struct {
     horizontal: Vec3,
     vertical: Vec3,
 
-    pub fn init() Camera {
-        const aspect_ratio = 16.0 / 9.0;
-        const viewport_height = 2.0;
+    pub fn init(
+        vfov: f32, // vertical field-of-view in degrees
+        aspect_ratio: f32,
+    ) Camera {
+        const theta = degrees_to_radians(vfov);
+        const h = tan(theta / 2);
+        const viewport_height = 2 * h;
         const viewport_width = aspect_ratio * viewport_height;
+
         const focal_length = 1.0;
         const origin = Point3.init(0, 0, 0);
         const horizontal = Vec3.init(viewport_width, 0.0, 0.0);
diff --git a/zigrtiow/src/main.zig b/zigrtiow/src/main.zig
index d543205..1fdd1cc 100644
--- a/zigrtiow/src/main.zig
+++ b/zigrtiow/src/main.zig
@@ -25,6 +25,9 @@ const Vec3 = vec.Vec3;
 const info = std.log.info;
 const random_in_hemisphere = vec.random_in_hemisphere;
 const write_color = color.write_color;
+const math = std.math;
+const pi = math.pi;
+const cos = math.cos;
 
 fn ray_color(r: Ray, world: Hittable, depth: isize) Color {
     // If we've exceeded the ray bounce limit, no more light is gathered.
@@ -87,22 +90,18 @@ pub fn main() anyerror!void {
     const max_depth = 50;
 
     // World
+    const r = cos(pi / @as(f32, 4.0));
     var tmp_world = HittableList.init();
 
-    const material_ground = Material{ .labertian = Labertian{ .albedo = Color.init(0.8, 0.8, 0.0) } };
-    const material_center = Material{ .labertian = Labertian{ .albedo = Color.init(0.1, 0.2, 0.5) } };
-    const material_left = Material{ .dielectric = Dielectric{ .ir = 1.5 } };
-    const material_right = Material{ .metal = Metal{ .albedo = Color.init(0.8, 0.6, 0.2), .fuzz = 0.0 } };
+    const material_left = Material{ .labertian = Labertian{ .albedo = Color.init(0, 0, 1) } };
+    const material_right = Material{ .labertian = Labertian{ .albedo = Color.init(1, 0, 0) } };
 
-    try tmp_world.add(Hittable{ .sphere = Sphere.init(Point3.init(0, -100.5, -1), 100, material_ground) });
-    try tmp_world.add(Hittable{ .sphere = Sphere.init(Point3.init(0, 0, -1), 0.5, material_center) });
-    try tmp_world.add(Hittable{ .sphere = Sphere.init(Point3.init(-1, 0, -1), 0.5, material_left) });
-    try tmp_world.add(Hittable{ .sphere = Sphere.init(Point3.init(-1, 0, -1), -0.4, material_left) });
-    try tmp_world.add(Hittable{ .sphere = Sphere.init(Point3.init(1, 0, -1), 0.5, material_right) });
+    try tmp_world.add(Hittable{ .sphere = Sphere.init(Point3.init(-r, 0, -1), r, material_left) });
+    try tmp_world.add(Hittable{ .sphere = Sphere.init(Point3.init(r, 0, -1), r, material_right) });
     const world = Hittable{ .hittable_list = tmp_world };
 
     // Camera
-    const cam = Camera.init();
+    const cam = Camera.init(90, aspect_ratio);
 
     // Render
     const Node = Queue(Task).Node;