From e5e5863c1d48cc335e4514476356d922c3fad29f Mon Sep 17 00:00:00 2001
From: Jean-Michel Gorius <jean-michel.gorius@protonmail.com>
Date: Fri, 11 Nov 2022 22:46:52 +0100
Subject: [PATCH] Parametrize the camera

---
 camera.c | 29 ++++++++++++++++++++---------
 camera.h |  5 +++--
 main.c   |  5 +++--
 3 files changed, 26 insertions(+), 13 deletions(-)

diff --git a/camera.c b/camera.c
index daa1c2b..504a466 100644
--- a/camera.c
+++ b/camera.c
@@ -1,23 +1,34 @@
 #include "camera.h"
+#include "point3.h"
+#include "utils.h"
+#include "vec3.h"
 
-void camera_init(Camera *camera, double aspect_ratio) {
-  double viewport_height = 2;
+#include <math.h>
+
+void camera_init(Camera *camera, Point3 look_from, Point3 look_at, Vec3 up,
+                 double vertical_fov, double aspect_ratio) {
+  double theta = degrees_to_radians(vertical_fov);
+  double h = tan(theta / 2.0);
+  double viewport_height = 2.0 * h;
   double viewport_width = aspect_ratio * viewport_height;
-  double focal_length = 1.0;
 
-  camera->origin = (Point3){0, 0, 0};
-  camera->horizontal = (Vec3){viewport_width, 0, 0};
-  camera->vertical = (Vec3){0, viewport_height, 0};
+  Vec3 w = vec3_normalize(point3_sub(look_from, look_at));
+  Vec3 u = vec3_normalize(vec3_cross(up, w));
+  Vec3 v = vec3_cross(w, u);
+
+  camera->origin = look_from;
+  camera->horizontal = vec3_mul(viewport_width, u);
+  camera->vertical = vec3_mul(viewport_height, v);
   Vec3 offset =
       vec3_add(vec3_div(camera->horizontal, 2), vec3_div(camera->vertical, 2));
-  offset = vec3_add(offset, (Vec3){0, 0, focal_length});
+  offset = vec3_add(offset, w);
   camera->lower_left_corner = point3_add(camera->origin, vec3_neg(offset));
 }
 
-Ray camera_get_ray(const Camera *camera, double u, double v) {
+Ray camera_get_ray(const Camera *camera, double s, double t) {
   Point3 screen_point = point3_add(
       camera->lower_left_corner,
-      vec3_add(vec3_mul(u, camera->horizontal), vec3_mul(v, camera->vertical)));
+      vec3_add(vec3_mul(s, camera->horizontal), vec3_mul(t, camera->vertical)));
   Vec3 direction = point3_sub(screen_point, camera->origin);
   return (Ray){camera->origin, direction};
 }
diff --git a/camera.h b/camera.h
index b9d1fb1..b839bc5 100644
--- a/camera.h
+++ b/camera.h
@@ -12,8 +12,9 @@ typedef struct Camera {
   Vec3 vertical;
 } Camera;
 
-void camera_init(Camera *camera, double aspect_ratio);
+void camera_init(Camera *camera, Point3 look_from, Point3 look_at, Vec3 up,
+                 double vertical_fov, double aspect_ratio);
 
-Ray camera_get_ray(const Camera *camera, double u, double v);
+Ray camera_get_ray(const Camera *camera, double s, double t);
 
 #endif /* INCLUDED_CAMERA_H */
diff --git a/main.c b/main.c
index b6f1577..7b2db58 100644
--- a/main.c
+++ b/main.c
@@ -74,7 +74,7 @@ int main(void) {
   Sphere sphere_inside_left = {
       .type = HITTABLE_SPHERE,
       .center = (Point3){-1.0, 0.0, -1.0},
-      .radius = -0.4,
+      .radius = -0.45,
       .material = (const Material *)&material_left,
   };
   Sphere sphere_right = {
@@ -91,7 +91,8 @@ int main(void) {
 
   /* Camera */
   Camera camera;
-  camera_init(&camera, aspect_ratio);
+  camera_init(&camera, (Point3){-2.0, 2.0, 1.0}, (Point3){0.0, 0.0, -1.0},
+              (Vec3){0.0, 1.0, 0.0}, 20, aspect_ratio);
 
   printf("P3\n%u %u\n255\n", image_width, image_height);