From e24fe740799a45097439834eeab8d73a9e311882 Mon Sep 17 00:00:00 2001
From: Rokas Puzonas <rokas.puz@gmail.com>
Date: Wed, 29 Nov 2023 23:35:01 +0200
Subject: [PATCH] add defocus blur

---
 src/camera.cpp | 31 ++++++++++++++++++++++---------
 src/main.cu    | 14 ++++++++++----
 2 files changed, 32 insertions(+), 13 deletions(-)

diff --git a/src/camera.cpp b/src/camera.cpp
index a7416ce..ffc456e 100644
--- a/src/camera.cpp
+++ b/src/camera.cpp
@@ -2,26 +2,39 @@
 
 #include "ray.cpp"
 
+__device__ vec3 random_in_unit_disk(curandState *local_rand_state) {
+    vec3 p;
+    do {
+        p = 2.0f*vec3(curand_uniform(local_rand_state), curand_uniform(local_rand_state), 0) - vec3(1,1,0);
+    } while(dot(p,p) >= 1.0f);
+    return p;
+}
+
 class camera {
 public:
-    __device__ camera(vec3 lookfrom, vec3 lookat, vec3 vup, float vfov, float aspect) {
+    __device__ camera(vec3 lookfrom, vec3 lookat, vec3 vup, float vfov, float aspect, float aperture, float focus_dist) {
+        lens_radius = aperture / 2.0f;
         float theta = vfov*M_PI/180;
         float half_height = tan(theta/2);
         float half_width  = aspect*half_height;
         origin = lookfrom;
-        vec3 w = unit_vector(lookfrom - lookat);
-        vec3 u = unit_vector(cross(vup, w));
-        vec3 v = cross(w, u);
-        lower_left_corner = origin - half_width*u - half_height*v - w;
-        horizontal = 2*half_width*u;
-        vertical   = 2*half_height*v;
+        w = unit_vector(lookfrom - lookat);
+        u = unit_vector(cross(vup, w));
+        v = cross(w, u);
+        lower_left_corner = origin - focus_dist*(half_width*u + half_height*v + w);
+        horizontal = 2*half_width*focus_dist*u;
+        vertical   = 2*half_height*focus_dist*v;
     }
-    __device__ ray get_ray(float u, float v) {
-        return ray(origin, lower_left_corner + u*horizontal + v*vertical - origin);
+    __device__ ray get_ray(float s, float t, curandState *local_rand_state) {
+        vec3 rd = lens_radius*random_in_unit_disk(local_rand_state);
+        vec3 offset = u * rd.x() + v * rd.y();
+        return ray(origin + offset, lower_left_corner + s*horizontal + t*vertical - origin - offset);
     }
 
     vec3 origin;
     vec3 lower_left_corner;
     vec3 horizontal;
     vec3 vertical;
+    vec3 u, v, w;
+    float lens_radius;
 };
diff --git a/src/main.cu b/src/main.cu
index b77bc51..2fb4f75 100644
--- a/src/main.cu
+++ b/src/main.cu
@@ -81,7 +81,7 @@ __global__ void render(vec3 *fb,
     for (int s = 0; s < ns; s++) {
         float u = float(x + curand_uniform(&local_rand_state)) / max_x;
         float v = float(y + curand_uniform(&local_rand_state)) / max_y;
-        ray r = (*cam)->get_ray(u,v);
+        ray r = (*cam)->get_ray(u,v, &local_rand_state);
         col += color(r, world, &local_rand_state);
     }
     rand_state[pixel_idx] = local_rand_state;
@@ -101,11 +101,17 @@ __global__ void create_world(hitable **d_list, int d_list_size, hitable **d_worl
         d_list[3] = new sphere(vec3(-1,    0  , -1),  0.5, new dielectric(1.5));
         d_list[4] = new sphere(vec3(-1,    0  , -1), -0.45, new dielectric(1.5));
         *d_world  = new hitable_list(d_list, d_list_size);
-        *d_camera = new camera(vec3(-2,2,1),
-                                vec3(0,0,-1),
+
+        vec3 lookfrom(3,3,2);
+        vec3 lookat(0,0,-1);
+        float dist_to_focus = (lookfrom-lookat).length();
+        float aperture = 2.0f;
+        *d_camera = new camera(lookfrom, lookat,
                                 vec3(0,1,0),
                                 20.0,
-                                float(nx)/float(ny));
+                                float(nx)/float(ny),
+                                aperture,
+                                dist_to_focus);
     }
 }