From 8d92cc861e897329eed0427f2b1e873d133be3d4 Mon Sep 17 00:00:00 2001
From: Bill Thiede <git@xinu.tv>
Date: Sat, 13 Aug 2022 20:57:46 -0700
Subject: [PATCH] zigrtiow: placeable camera and helpers for creating
 materials.

---
 zigrtiow/src/camera.zig   | 21 ++++++++++++++-------
 zigrtiow/src/main.zig     | 19 +++++++++++++------
 zigrtiow/src/material.zig | 12 ++++++++++++
 zigrtiow/src/vec.zig      |  3 +++
 4 files changed, 42 insertions(+), 13 deletions(-)

diff --git a/zigrtiow/src/camera.zig b/zigrtiow/src/camera.zig
index fce465b..8232728 100644
--- a/zigrtiow/src/camera.zig
+++ b/zigrtiow/src/camera.zig
@@ -22,6 +22,9 @@ pub const Camera = struct {
     vertical: Vec3,
 
     pub fn init(
+        lookfrom: Point3,
+        lookat: Point3,
+        vup: Vec3,
         vfov: f32, // vertical field-of-view in degrees
         aspect_ratio: f32,
     ) Camera {
@@ -30,19 +33,23 @@ pub const Camera = struct {
         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);
-        const vertical = Vec3.init(0.0, viewport_height, 0.0);
+        const w = lookfrom.sub(lookat).unit();
+        const u = vup.cross(w).unit();
+        const v = w.cross(u);
+
+        const origin = lookfrom;
+        const horizontal = u.scale(viewport_width);
+        const vertical = v.scale(viewport_height);
+        const lower_left_corner = origin.sub(horizontal.scale(0.5)).sub(vertical.scale(0.5)).sub(w);
 
         return Camera{
             .origin = origin,
             .horizontal = horizontal,
             .vertical = vertical,
-            .lower_left_corner = origin.sub(horizontal.scale(0.5)).sub(vertical.scale(0.5)).sub(Vec3.init(0, 0, focal_length)),
+            .lower_left_corner = lower_left_corner,
         };
     }
-    pub fn get_ray(camera: Camera, u: f32, v: f32) Ray {
-        return Ray.init(camera.origin, camera.lower_left_corner.add(camera.horizontal.scale(u).add(camera.vertical.scale(v).sub(camera.origin))));
+    pub fn get_ray(camera: Camera, s: f32, t: f32) Ray {
+        return Ray.init(camera.origin, camera.lower_left_corner.add(camera.horizontal.scale(s).add(camera.vertical.scale(t).sub(camera.origin))));
     }
 };
diff --git a/zigrtiow/src/main.zig b/zigrtiow/src/main.zig
index 1fdd1cc..6705770 100644
--- a/zigrtiow/src/main.zig
+++ b/zigrtiow/src/main.zig
@@ -28,6 +28,9 @@ const write_color = color.write_color;
 const math = std.math;
 const pi = math.pi;
 const cos = math.cos;
+const create_labertian = material.create_labertian;
+const create_metal = material.create_metal;
+const create_dielectric = material.create_dielectric;
 
 fn ray_color(r: Ray, world: Hittable, depth: isize) Color {
     // If we've exceeded the ray bounce limit, no more light is gathered.
@@ -90,18 +93,22 @@ 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_left = Material{ .labertian = Labertian{ .albedo = Color.init(0, 0, 1) } };
-    const material_right = Material{ .labertian = Labertian{ .albedo = Color.init(1, 0, 0) } };
+    const material_ground = create_labertian(Color.init(0.8, 0.8, 0));
+    const material_center = create_labertian(Color.init(0.1, 0.2, 0.5));
+    const material_left = create_dielectric(1.5);
+    const material_right = create_metal(Color.init(0.8, 0.6, 0.2), 0.0);
 
-    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) });
+    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), -0.45, material_left) });
+    try tmp_world.add(Hittable{ .sphere = Sphere.init(Point3.init(1, 0, -1), 0.5, material_right) });
     const world = Hittable{ .hittable_list = tmp_world };
 
     // Camera
-    const cam = Camera.init(90, aspect_ratio);
+    const cam = Camera.init(Point3.init(-2, 2, 1), Point3.init(0, 0, -1), Vec3.init(0, 1, 0), 20, aspect_ratio);
 
     // Render
     const Node = Queue(Task).Node;
diff --git a/zigrtiow/src/material.zig b/zigrtiow/src/material.zig
index 71c42c5..084f265 100644
--- a/zigrtiow/src/material.zig
+++ b/zigrtiow/src/material.zig
@@ -9,6 +9,18 @@ const random_unit_vector = vec.random_unit_vector;
 const random_in_unit_sphere = vec.random_in_unit_sphere;
 const pow = std.math.pow;
 
+pub fn create_labertian(albedo: Vec3) Material {
+    return Material{ .labertian = Labertian{ .albedo = albedo } };
+}
+
+pub fn create_metal(albedo: Vec3, fuzz: f32) Material {
+    return Material{ .metal = Metal{ .albedo = albedo, .fuzz = fuzz } };
+}
+
+pub fn create_dielectric(ir: f32) Material {
+    return Material{ .dielectric = Dielectric{ .ir = ir } };
+}
+
 pub const Material = union(enum) {
     labertian: Labertian,
     metal: Metal,
diff --git a/zigrtiow/src/vec.zig b/zigrtiow/src/vec.zig
index fc91855..ba13406 100644
--- a/zigrtiow/src/vec.zig
+++ b/zigrtiow/src/vec.zig
@@ -47,6 +47,9 @@ pub const Vec3 = struct {
         const t = u.v * v.v;
         return t[0] + t[1] + t[2];
     }
+    pub fn cross(u: Vec3, v: Vec3) Vec3 {
+        return Vec3.init(u.v[1] * v.v[2] - u.v[2] * v.v[1], u.v[2] * v.v[0] - u.v[0] * v.v[2], u.v[0] * v.v[1] - u.v[1] * v.v[0]);
+    }
     /// Return value in unit cube from -1, 1
     pub fn random() Vec3 {
         return Vec3.init(