Add ability to change FOV

compile_commands.json

@@ -71,11 +71,11 @@
       "-x",
       "c",
       "-o",
-      "/tmp/main-b05c2f.o",
+      "/tmp/main-f47303.o",
       "main.c"
     ],
     "directory": "/home/abdelrahman/Sources/programming/starfield",
     "file": "/home/abdelrahman/Sources/programming/starfield/main.c",
-    "output": "/tmp/main-b05c2f.o"
+    "output": "/tmp/main-f47303.o"
   }
 ]

main.c

@@ -1,5 +1,6 @@
 #include "aliases.h"
 #include <SDL2/SDL.h>
+#include <SDL2/SDL_keycode.h>
 #include <SDL2/SDL_pixels.h>
 #include <SDL2/SDL_rect.h>
 #include <SDL2/SDL_render.h>
@@ -8,6 +9,7 @@
 #include <SDL2/SDL_video.h>
 #include <math.h>
 #include <stdbool.h>
+#include <stdio.h>
 #include <stdlib.h>
 #include <time.h>
 
@@ -26,6 +28,13 @@
 
 #define PROJECTION_PLANE 1.0
 
+#define RAD(DEG) ((DEG * M_PI) / 180.0)
+#define DEG(RAD) ((RAD * 180.0) / M_PI)
+
+#define FOV_MIN 1.0
+#define FOV_MAX 170.0
+#define FOV_INC 3.0
+
 typedef struct {
   u32 x;
   u32 y;
@@ -58,7 +67,7 @@ void init_starfield(vec3f_t *stars, u32 count, i32 spread);
 void update_startfield(vec3f_t *stars, u32 count, i32 spread, u32 speed,
                        f64 delta);
 void render_starfield(SDL_Surface *surface, vec3f_t *stars, u32 count,
-                      i32 spread);
+                      i32 spread, f64 fov);
 
 int main(void) {
   srand(time(NULL));
@@ -83,6 +92,7 @@ int main(void) {
   init_starfield(stars, STAR_COUNT, STAR_SPREAD);
 
   f64 delta = 1.0 / 60.0; // constant delta
+  f64 fov = 60.0;
 
   while (running) {
     while (SDL_PollEvent(&event)) {
@@ -90,6 +100,26 @@ int main(void) {
       case SDL_QUIT:
         running = false;
         break;
+      case SDL_KEYDOWN:
+        switch (event.key.keysym.sym) {
+        case SDLK_UP:
+          fov -= FOV_INC;
+
+          if (fov < FOV_MIN) {
+            fov = FOV_MIN;
+          }
+
+          break;
+        case SDLK_DOWN:
+          fov += FOV_INC;
+
+          if (fov > FOV_MAX) {
+            fov = FOV_MAX;
+          }
+
+          break;
+        }
+        break;
       }
     }
 
@@ -97,7 +127,7 @@ int main(void) {
 
     render_clear(canvas, BG_COLOR);
 
-    render_starfield(canvas, stars, STAR_COUNT, STAR_SPREAD);
+    render_starfield(canvas, stars, STAR_COUNT, STAR_SPREAD, fov);
 
     SDL_BlitSurface(canvas, NULL, surface, NULL);
 
@@ -215,17 +245,19 @@ void update_startfield(vec3f_t *stars, u32 count, i32 spread, u32 speed,
 }
 
 void render_starfield(SDL_Surface *surface, vec3f_t *stars, u32 count,
-                      i32 spread) {
+                      i32 spread, f64 fov) {
   vec2f_t projected[count];
   vec2i_t coords;
 
+  f64 tangent = tan(RAD(fov * 0.5));
+
   for (u32 i = 0; i < count; ++i) {
     if (stars[i].z == 0.0) {
       continue;
     }
 
-    projected[i] =
+    projected[i] = (vec2f_t){.x = stars[i].x / stars[i].z / tangent,
-        (vec2f_t){.x = stars[i].x / stars[i].z, .y = stars[i].y / stars[i].z};
+                             .y = stars[i].y / stars[i].z / tangent};
 
     if (projected[i].x < NORMALISED_MIN || projected[i].x > NORMALISED_MAX ||
         projected[i].y < NORMALISED_MIN || projected[i].y > NORMALISED_MAX ||