Remove focal_len parameter from camera (hard-code as 1.0)

src/camera.c

@@ -16,6 +16,7 @@
 #define MAX_ITER 10
 #define MIN_T 1e-6
 #define SAMPLE_STDDEV 0.333
+#define FOCAL_LEN 1.0
 
 #define GAMMA 2.2
 
@@ -117,15 +118,15 @@ static int render_thread(void *arg)
 }
 
 camera_t camera_init(
-    vec3_t pos, double focal_len, double fov, uint32_t img_width,
-    uint32_t img_height, unsigned samples_per_pixel)
+    vec3_t pos, double fov, uint32_t img_width, uint32_t img_height,
+    unsigned samples_per_pixel)
 {
 	const double aspect = (double)img_width / (double)img_height;
 
 	const double fov_rad = M_PI * fov / 180.0;
-	const double viewport_height = focal_len * tan(fov_rad / 2);
+	const double viewport_height = FOCAL_LEN * tan(fov_rad / 2);
 	const double viewport_width = viewport_height * aspect;
-	const vec3_t viewport_disp = { 0, 0, focal_len };
+	const vec3_t viewport_disp = { 0, 0, FOCAL_LEN };
 
 	const vec3_t u = { viewport_width, 0, 0 };
 	const vec3_t v = { 0, -viewport_height, 0 };