From 0a30234b2681c8209c64a14c1d25aa6f769026d7 Mon Sep 17 00:00:00 2001
From: K Tyl <me@ktyl.dev>
Date: Wed, 3 Jun 2020 01:56:59 +0100
Subject: [PATCH] add ray

---
 src/main.cpp | 32 ++++++++++++++++++++++++++------
 src/ray.h    | 25 +++++++++++++++++++++++++
 2 files changed, 51 insertions(+), 6 deletions(-)
 create mode 100644 src/ray.h

diff --git a/src/main.cpp b/src/main.cpp
index 88385a1..bcdf74c 100755
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,23 +1,43 @@
 #include "colour.h"
 #include "vec3.h"
+#include "ray.h"
 
 #include <iostream>
 
-const int WIDTH = 256;
-const int HEIGHT = 256;
+const double ASPECT_RATIO = 16.0 / 9.0;
+const int WIDTH = 384;
+const int HEIGHT = static_cast<int>(WIDTH / ASPECT_RATIO);
+
+colour rayColour(const ray& r)
+{
+    vec3 unitDirection = unitVector(r.direction());
+    double t = 0.5 * (unitDirection.y() + 1.0);
+    return (1.0-t) * colour(1.0,1.0,1.0) + t*colour(0.5, 0.7, 1.0);
+}
 
 int main()
 {
-    std::cout << "P3" << std::endl;
-    std::cout << WIDTH << ' ' << HEIGHT << "\n255\n";
+    auto viewportHeight = 2.0;
+    auto viewportWidth = ASPECT_RATIO * viewportHeight;
+    auto focalLength = 1.0;
+
+    auto origin = point3(0, 0, 0);
+    auto horizontal = vec3(viewportWidth, 0, 0);
+    auto vertical = vec3(0, viewportHeight, 0);
+    auto lowerLeftCorner = origin - horizontal/2 - vertical/2 - vec3(0,0,focalLength);
+
+    std::cout << "P3\n" << WIDTH << ' ' << HEIGHT << "\n255\n";
 
     for (int y = HEIGHT - 1; y >= 0; --y)
     {
         std::cerr << "\rScanlines remaining: " << y << ' ' << std::flush;
-
         for (int x = 0; x < WIDTH; ++x)
         {
-            colour pixelColour(double(x)/(WIDTH-1), double(y)/(HEIGHT-1), 0.25);
+            auto u = double(x) / (WIDTH-1);
+            auto v = double(y) / (HEIGHT-1);
+            ray r(origin, lowerLeftCorner + u*horizontal + v*vertical - origin);
+            
+            colour pixelColour = rayColour(r);
             writeColour(std::cout, pixelColour);
         }
     }
diff --git a/src/ray.h b/src/ray.h
new file mode 100644
index 0000000..83690b5
--- /dev/null
+++ b/src/ray.h
@@ -0,0 +1,25 @@
+#pragma once
+
+#include "vec3.h"
+
+class ray
+{
+public:
+    ray() {}
+    ray(const point3& origin, const vec3& direction) : 
+        origin_(origin), 
+        direction_(direction) 
+    {}
+
+    point3  origin()    const { return origin_; }
+    vec3    direction() const { return direction_; }
+
+    point3 at(double t) const
+    {
+        return origin_ + t * direction_;
+    }
+
+private:
+    point3  origin_;
+    vec3    direction_;
+};