Sending Rays Into the Scene

1 files changed, 36 insertions, 4 deletions

diff --git a/apps/main.cc b/apps/main.cc
index b0b3aa4..d5702cd 100644
--- a/apps/main.cc
+++ b/apps/main.cc
@@ -15,16 +15,45 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 #include "color.h"
+#include "ray.h"
 #include "vec3.h"
 
 #include <iostream>
 
+color ray_color( const ray& r )
+{
+  vec3 unit_direction = unit_vector( r.direction() );
+  auto a = 0.5 * ( unit_direction.y() + 1.0 );
+  return ( 1.0 - a ) * color( 1.0, 1.0, 1.0 ) + a * color( 0.5, 0.7, 1.0 );
+}
+
 int main()
 {
   // Image
 
-  const int image_width = 256;
-  const int image_height = 256;
+  auto aspect_ratio = 16.0 / 9.0;
+  const int image_width = 400;
+  // Calculate the image height, and ensure that it's at least 1.
+  int image_height = static_cast<int>( image_width / aspect_ratio );
+  image_height = ( image_height < 1 ) ? 1 : image_height;
+
+  // Camera
+  auto focal_length = 1.0;
+  auto viewport_height = 2.0;
+  auto viewport_width = viewport_height * ( double( image_width ) / image_height );
+  auto camera_center = point3( 0, 0, 0 );
+
+  // Calculate the vectors across the horizontal and down the vertical viewport edges.
+  auto viewport_u = vec3( viewport_width, 0, 0 );
+  auto viewport_v = vec3( 0, -viewport_height, 0 );
+
+  // Calculate the horizontal and vertical delta vectors from pixel to pixel.
+  auto pixel_delta_u = viewport_u / image_width;
+  auto pixel_delta_v = viewport_v / image_height;
+
+  // Calculate the location of the upper left pixel.
+  auto viewport_upper_left = camera_center - vec3( 0, 0, focal_length ) - viewport_u / 2 - viewport_v / 2;
+  auto pixel00_loc = viewport_upper_left + 0.5 * ( pixel_delta_u + pixel_delta_v );
 
   // Render
 
@@ -32,8 +61,11 @@ int main()
   for ( int j = 0; j < image_height; j++ ) {
     std::clog << "\rScanlines remaining: " << ( image_height - j ) << ' ' << std::flush;
     for ( int i = 0; i < image_width; i++ ) {
-      auto pixel_color = color(
-        static_cast<double>( i ) / ( image_width - 1 ), static_cast<double>( j ) / ( image_height - 1 ), 0 );
+      auto pixel_center = pixel00_loc + ( i * pixel_delta_u ) + ( j * pixel_delta_v );
+      auto ray_direction = pixel_center - camera_center;
+      ray r( camera_center, ray_direction );
+
+      const color pixel_color = ray_color( r );
       write_color( std::cout, pixel_color );
     }
   }