Finished chapter 4.

build.sh

@@ -1,7 +1,7 @@
 #!/bin/sh
 mkdir -p build
 pushd build
-rm -rf *
+rm -rf sdl_platform.dSYM
 
 # Plugin library
 c++ -Wall -std=c++11 -c -fpic -g ../code/rt_weekend.cpp -o librt_weekend.o

code/ray.h

@@ -1,5 +1,5 @@
-#ifndef RAYH
-#define RAYH
+#ifndef RAY_H
+#define RAY_H
 
 #include "vec3.h"
 

code/rt_weekend.cpp

@@ -1,17 +1,18 @@
 #include "rt_weekend.h"
 #include "ray.h"
 
-bool hit_sphere(const vec3& center, float radius, const ray& r)
+bool hit_sphere(const vec3 &center, float radius, const ray &r)
 {
     vec3 oc = r.origin() - center;
     float a = dot(r.direction(), r.direction());
     float b = 2.0 * dot(oc, r.direction());
     float c = dot(oc, oc) - radius * radius;
     float discriminant = b * b - 4 * a * c;
+
     return (discriminant > 0);
 }
 
-vec3 color(const ray& r)
+vec3 color (const ray &r)
 {
     if (hit_sphere(vec3(0, 0, -1), 0.5, r))
         return vec3(1, 0, 0);
@@ -26,21 +27,25 @@ PluginUpdateAndRender(plugin_offscreen_buffer *Buffer)
 {
     int Pitch = Buffer->Pitch;
     uint8_t *Row = (uint8_t *)Buffer->Memory;
-    for(int Y = 0;
-        Y < Buffer->Height;
-        ++Y)
+
+    vec3 lower_left_corner(-2.0, -1.0, -1.0);
+    vec3 horizontal(4.0, 0.0, 0.0);
+    vec3 vertical(0.0, 2.0, 0.0);
+    vec3 origin(0.0, 0.0, 0.0);
+
+
+    for(int j = Buffer->Height - 1; j >= 0; j--)
     {
         uint32_t *Pixel = (uint32_t *)Row;
-        for(int X = 0;
-            X < Buffer->Width;
-            ++X)
+        for(int i = 0; i < Buffer->Width; i++)
         {
-            float r = float(X) / float(Buffer->Width);
-            float g = float(Y) / float(Buffer->Height);
-            float b = 0.2;
-            int ir = int(255.99 * r);
-            int ig = int(255.99 * g);
-            int ib = int(255.99 * b);
+            float u = float(i) / float(Buffer->Width);
+            float v = float(j) / float(Buffer->Height);
+            ray r(origin, lower_left_corner + u * horizontal + v * vertical);
+            vec3 col = color(r);
+            int ir = int(255.99 * col[0]);
+            int ig = int(255.99 * col[1]);
+            int ib = int(255.99 * col[2]);
 
             *Pixel++ = (ir << 24) + (ig << 16) + (ib << 8) + 0xFF;
         }

code/sdl_platform.cpp

@@ -12,7 +12,7 @@
 
 const char *WindowTitle = "Ray Tracing in a Weekend";
 
-const uint32_t TARGET_FRAME_RATE = 30;
+const uint32_t TARGET_FRAME_RATE = 15;
 const uint32_t TICKS_PER_FRAME = 1000 / TARGET_FRAME_RATE;
 const uint32_t WINDOW_WIDTH = 500;
 const uint32_t WINDOW_HEIGHT = 250;