main.cpp

#include "vec3.h"
#include "color.h"
#include "ray.h"
#include "hittable.h"
#include "sphere.h"
#include "hittable_list.h"
#include "rtweekend.h"
#include<iostream>


color ray_color(const ray& r, const hittable& world){ 
  //Check if the ray hits any object in the world
  hit_record rec;
  if(world.hit(r,0,infinity,rec)){
    return 0.5* (rec.normal + color(1,1,1));
  } 

  vec3 unit_direction= unit_vector(r.direction());
  auto a= 0.5*(unit_direction.y()+1.0); // 0 means the ray is pointing down, 1 means the ray is pointing up
  return (1.0-a) * color(1.0,1.5,1.0) + a*color(0.5,0.7,1.0); // smooth gradient background with white and light blue colors
}

int main(){
  
  // Image
  auto ratio= 16.0/9.0;
  int image_width= 800;

  //Calculate height based on aspect ratio
  int image_height= int(image_width/ratio);
  image_height= (image_height<1)? 1 : image_height; // ensure height is at least 1 
  
  //world
  hittable_list world;
  world.add(make_shared<sphere>(point3(0,0,-1),0.5));  //makes sphere at center
  world.add(make_shared<sphere>(point3(0,-100.5,-1),100));   //creates ground sphere
  world.add(make_shared<sphere>(point3(-0.5,0,-1),0.3));  //makes sphere at left
  world.add(make_shared<sphere>(point3(0.5,0,-1),0.3));  //makes sphere at right

  //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 horizonal and down the vertical viewport edges
  auto viewport_u= vec3(viewport_width,0,0);
  auto viewport_v= vec3(0,-viewport_height,0);

  //Calculate the horizonal 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 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 the image 
  std::cout<<"P3\n"<<image_width<<" "<<image_height<<"\n255\n";

  for(int j=0;j<image_height;j++){
    std::clog<<"Scanlines remaining: "<<image_height-j<<"\n"<<std::flush;
    for(int i=0;i<image_width;i++){

      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);

      color pixel_color= ray_color(r,world);
      write_color(std::cout, pixel_color);
    }
  }
  std::clog<<"\rDone. \n";
  return 0;
}