add camera controls

src/camera.h

@@ -26,8 +26,10 @@ public:
 
   void move_to(Point3 loc) { center = loc; }
 
+  Point3 position() { return center; }
+
 private:
-  int image_height;   // Rendered image height
+  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

src/main.cpp

@@ -1,3 +1,4 @@
+#include "camera.h"
 #include "canvas.h"
 #include "simulation.h"
 #include <SDL2/SDL.h>
@@ -14,9 +15,14 @@ int main() {
 
   Canvas canvas(image_width, image_height);
   RingBuffer<SimulationState> buffer(64);
+  Camera cam;
+  cam.aspect_ratio = 16.0 / 9.0;
+  cam.image_width = 400;
+  cam.move_to(Point3(0, 10, 100));
 
   std::thread sim(simulation_thread, std::ref(buffer));
-  std::thread render(render_thread, std::ref(buffer), std::ref(canvas));
+  std::thread render(render_thread, std::ref(buffer), std::ref(canvas),
+                     std::ref(cam));
 
   SDL_Init(SDL_INIT_VIDEO);
   int scale = 3;
@@ -32,6 +38,8 @@ int main() {
                                            SDL_TEXTUREACCESS_STREAMING,
                                            canvas.width, canvas.height);
 
+  float camera_speed = 10.0f; // tweak as needed
+
   while (running) {
     void *pixels;
     int pitch;
@@ -44,10 +52,36 @@ int main() {
     SDL_RenderCopy(renderer, texture, nullptr, &dest);
     SDL_RenderPresent(renderer);
 
+    Point3 move(0, 0, 0);
+
     SDL_Event e;
     while (SDL_PollEvent(&e)) {
-      if (e.type == SDL_QUIT)
+      if (e.type == SDL_QUIT) {
         running = false;
+      } else if (e.type == SDL_KEYDOWN) {
+        switch (e.key.keysym.sym) {
+        case SDLK_w:
+          move.z() -= camera_speed;
+          break; // forward
+        case SDLK_s:
+          move.z() += camera_speed;
+          break; // backward
+        case SDLK_a:
+          move.x() -= camera_speed;
+          break; // left
+        case SDLK_d:
+          move.x() += camera_speed;
+          break; // right
+        case SDLK_q:
+          move.y() += camera_speed;
+          break; // up
+        case SDLK_e:
+          move.y() -= camera_speed;
+          break; // down
+        }
+
+        cam.move_to(cam.position() + move); // assuming cam.position exists
+      }
     }
 
     std::this_thread::sleep_for(std::chrono::milliseconds(16)); // ~60fps

src/simulation.cpp

@@ -64,47 +64,29 @@ void simulation_thread(RingBuffer<SimulationState> &buffer) {
 
       size_t n_bodies = state.bodies.size();
       for (size_t m1_idx = 0; m1_idx < n_bodies; m1_idx++) {
-        Vec3 a_g = {0, 0, 0};
+        Vec3 a_g;
 
         for (size_t m2_idx = 0; m2_idx < n_bodies; m2_idx++) {
           if (m2_idx != m1_idx) {
-            Vec3 r_vector;
+            Vec3 r_vector =
+                state.bodies[m1_idx].position - state.bodies[m2_idx].position;
+            double r_mag = r_vector.length();
 
-            r_vector.x() = state.bodies[m1_idx].position.x() -
-                           state.bodies[m2_idx].position.x();
-            r_vector.y() = state.bodies[m1_idx].position.y() -
-                           state.bodies[m2_idx].position.y();
-            r_vector.z() = state.bodies[m1_idx].position.z() -
-                           state.bodies[m2_idx].position.z();
+            double acceleration =
+                -BIG_G * state.bodies[m2_idx].mass / (r_mag * r_mag);
 
-            float r_mag =
-                sqrt(r_vector.x() * r_vector.x() + r_vector.y() * r_vector.y() +
-                     r_vector.z() * r_vector.z());
+            Vec3 r_unit_vector = r_vector / r_mag;
 
-            float acceleration =
-                -1.0 * BIG_G * (state.bodies[m2_idx].mass) / pow(r_mag, 2.0);
-
-            Vec3 r_unit_vector = {r_vector.x() / r_mag, r_vector.y() / r_mag,
-                                  r_vector.z() / r_mag};
-
-            a_g.x() += acceleration * r_unit_vector.x();
-            a_g.y() += acceleration * r_unit_vector.y();
-            a_g.z() += acceleration * r_unit_vector.z();
+            a_g += r_unit_vector * acceleration;
           }
         }
 
-        state.bodies[m1_idx].velocity.x() += a_g.x() * bdt;
-        state.bodies[m1_idx].velocity.y() += a_g.y() * bdt;
-        state.bodies[m1_idx].velocity.z() += a_g.z() * bdt;
+        state.bodies[m1_idx].velocity += a_g * bdt;
       }
 
       for (size_t entity_idx = 0; entity_idx < n_bodies; entity_idx++) {
-        state.bodies[entity_idx].position.x() +=
-            state.bodies[entity_idx].velocity.x() * bdt;
-        state.bodies[entity_idx].position.y() +=
-            state.bodies[entity_idx].velocity.y() * bdt;
-        state.bodies[entity_idx].position.z() +=
-            state.bodies[entity_idx].velocity.z() * bdt;
+        state.bodies[entity_idx].position +=
+            state.bodies[entity_idx].velocity * bdt;
       }
 
       // Try to push it into the buffer
@@ -124,12 +106,7 @@ void simulation_thread(RingBuffer<SimulationState> &buffer) {
 /**
  * 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, 10, 100));
-
+void render_thread(RingBuffer<SimulationState> &buffer, Canvas &canvas, Camera &cam) {
   while (running) {
     auto maybe_state = buffer.pop();
     if (maybe_state.has_value()) {

src/simulation.h

@@ -2,8 +2,8 @@
 #define SIMULATION_H
 
 #include "canvas.h"
+#include "camera.h"
 #include "ring_buffer.h"
-#include "vec3.h"
 #include <atomic>
 #include <memory>
 #include <mutex>
@@ -25,6 +25,6 @@ struct SimulationState {
 extern std::atomic<bool> running;
 
 void simulation_thread(RingBuffer<SimulationState> &buffer);
-void render_thread(RingBuffer<SimulationState> &buffer, Canvas &canvas);
+void render_thread(RingBuffer<SimulationState> &buffer, Canvas &canvas, Camera &cam);
 
 #endif