add camera

src/camera.h

@@ -0,0 +1,73 @@
+#ifndef CAMERA_H
+#define CAMERA_H
+
+#include "common.h"
+#include "hittable.h"
+
+class Camera {
+public:
+  double aspect_ratio = 1.0; // Ratio of image width over height
+  int image_width = 100;     // Rendered image width in pixel count
+
+  void render(const hittable &world, Canvas &canvas) {
+    initialize();
+
+    for (int j = 0; j < canvas.height; j++) {
+      for (int i = 0; i < canvas.width; i++) {
+        auto pixel_center =
+            pixel00_loc + (i * pixel_delta_u) + (j * pixel_delta_v);
+        auto ray_direction = pixel_center - center;
+        Ray r(center, ray_direction);
+
+        canvas.set_pixel(i, j, ray_color(r, world));
+      }
+    }
+  }
+
+  void move_to(Point3 loc) { center = loc; }
+
+private:
+  int image_height;   // Rendered image height
+  Point3 center = Point3(0, 0, 0);
+  Point3 pixel00_loc; // Location of pixel 0, 0
+  Vec3 pixel_delta_u; // Offset to pixel to the right
+  Vec3 pixel_delta_v; // Offset to pixel below
+
+  void initialize() {
+    image_height = int(image_width / aspect_ratio);
+    image_height = (image_height < 1) ? 1 : image_height;
+
+    // Determine viewport dimensions.
+    auto focal_length = 1.0;
+    auto viewport_height = 2.0;
+    auto viewport_width =
+        viewport_height * (double(image_width) / image_height);
+
+    // 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.
+    pixel_delta_u = viewport_u / image_width;
+    pixel_delta_v = viewport_v / image_height;
+
+    // Calculate the location of the upper left pixel.
+    auto viewport_upper_left =
+        center - Vec3(0, 0, focal_length) - viewport_u / 2 - viewport_v / 2;
+    pixel00_loc = viewport_upper_left + 0.5 * (pixel_delta_u + pixel_delta_v);
+  }
+
+  Color ray_color(const Ray &r, const hittable &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);
+    return (1.0 - a) * Color(1.0, 1.0, 1.0) + a * Color(0.5, 0.7, 1.0);
+  }
+};
+
+#endif

src/simulation.cpp

@@ -1,6 +1,6 @@
 #include "simulation.h"
+#include "camera.h"
 #include "common.h"
-#include "hittable.h"
 #include "hittable_list.h"
 #include "sphere.h"
 
@@ -124,73 +124,32 @@ void simulation_thread(RingBuffer<SimulationState> &buffer) {
   }
 }
 
-Color ray_color(const Ray &r, const hittable &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);
-  return (1.0 - a) * Color(1.0, 1.0, 1.0) + a * Color(0.5, 0.7, 1.0);
-}
-
-/**
- * Render raytracing.
- */
-void render(SimulationState state, Canvas &canvas) {
-  hittable_list world;
-
-  const double SCALE = 1e9;
-
-  for (auto b : state.bodies) {
-    // we need to swap y and z because the raytracter uses opengl style coordinates
-    auto bb = b.position / SCALE;
-    world.add(make_shared<sphere>(Vec3(bb.x(), bb.z(), bb.y()), b.radius));
-  }
-
-  // Camera
-  auto focal_length = 1.0;
-  auto viewport_height = 2.0;
-  auto viewport_width = viewport_height * (float(canvas.width) / canvas.height);
-  auto camera_center = Point3(0, 0, 100);
-
-  // 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 / canvas.width;
-  auto pixel_delta_v = viewport_v / canvas.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);
-
-  for (int j = 0; j < canvas.height; j++) {
-    for (int i = 0; i < canvas.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);
-
-      canvas.set_pixel(i, j, ray_color(r, world));
-    }
-  }
-}
-
 /**
  * Render thread.
  */
 void render_thread(RingBuffer<SimulationState> &buffer, Canvas &canvas) {
+  Camera cam;
+  cam.aspect_ratio = 16.0 / 9.0;
+  cam.image_width = 400;
+  cam.move_to(Point3(0, 0, 100));
+
   while (running) {
     auto maybe_state = buffer.pop();
     if (maybe_state.has_value()) {
       const SimulationState &state = maybe_state.value();
-      render(state, canvas); // Pure function: write pixel colors into canvas
+
+      hittable_list world;
+
+      const double SCALE = 1e9;
+
+      for (auto b : state.bodies) {
+        // we need to swap y and z because the raytracter uses opengl style
+        // coordinates
+        auto bb = b.position / SCALE;
+        world.add(make_shared<sphere>(Vec3(bb.x(), bb.z(), bb.y()), b.radius));
+      }
+
+      cam.render(world, canvas);
     } else {
       std::this_thread::sleep_for(std::chrono::milliseconds(1));
     }