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Update image generation code
Generally, define aspect ratio up front, then derive image height from that and the image width. This change also fixes an issue where the sampling was slightly off due to an off-by-one error when computing the image basis vectors. Finally, some naming and commenting tweaks to `aspect_ratio` and `vfov`.
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6 files changed

+43
-41
lines changed

6 files changed

+43
-41
lines changed

‎books/RayTracingInOneWeekend.html

Lines changed: 24 additions & 24 deletions
Original file line numberDiff line numberDiff line change
@@ -466,9 +466,9 @@
466466
}
467467

468468
int main() {
469-
const int image_width = 768;
470-
const auto aspect_ratio = 9.0 / 16.0;
471-
const int image_height = static_cast<int>(aspect_ratio * image_width);
469+
const auto aspect_ratio = 16.0 / 9.0;
470+
const int image_width = 384;
471+
const int image_height = static_cast<int>(image_width / aspect_ratio);
472472

473473
std::cout << "P3\n" << image_width << " " << image_height << "\n255\n";
474474

@@ -1180,8 +1180,9 @@
11801180
}
11811181

11821182
int main() {
1183-
const int image_width = 200;
1184-
const int image_height = 100;
1183+
const auto aspect_ratio = 16.0 / 9.0;
1184+
const int image_width = 384;
1185+
const int image_height = static_cast<int>(image_width / aspect_ratio);
11851186

11861187
std::cout << "P3\n" << image_width << ' ' << image_height << "\n255\n";
11871188

@@ -1373,8 +1374,9 @@
13731374

13741375
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
13751376
int main() {
1376-
const int image_width = 200;
1377-
const int image_height = 100;
1377+
const auto aspect_ratio = 16.0 / 9.0;
1378+
const int image_width = 384;
1379+
const int image_height = static_cast<int>(image_width / aspect_ratio);
13781380
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
13791381
const int samples_per_pixel = 100;
13801382
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
@@ -1553,8 +1555,9 @@
15531555
...
15541556

15551557
int main() {
1556-
const int image_width = 200;
1557-
const int image_height = 100;
1558+
const auto aspect_ratio = 16.0 / 9.0;
1559+
const int image_width = 384;
1560+
const int image_height = static_cast<int>(image_width / aspect_ratio);
15581561
const int samples_per_pixel = 100;
15591562
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
15601563
const int max_depth = 50;
@@ -2076,8 +2079,9 @@
20762079

20772080
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
20782081
int main() {
2079-
const int image_width = 200;
2080-
const int image_height = 100;
2082+
const auto aspect_ratio = 16.0 / 9.0;
2083+
const int image_width = 384;
2084+
const int image_height = static_cast<int>(image_width / aspect_ratio);
20812085
const int samples_per_pixel = 100;
20822086
const int max_depth = 50;
20832087

@@ -2563,14 +2567,14 @@
25632567
public:
25642568
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
25652569
camera(
2566-
double vfov, // top to bottom, in degrees
2567-
double aspect
2570+
double vfov, // vertical field-of-view in degrees
2571+
double aspect_ratio
25682572
) {
25692573
origin = point3(0.0, 0.0, 0.0);
25702574

25712575
auto theta = degrees_to_radians(vfov);
25722576
auto half_height = tan(theta/2);
2573-
auto half_width = aspect * half_height;
2577+
auto half_width = aspect_ratio * half_height;
25742578

25752579
lower_left_corner = point3(-half_width, -half_height, -1.0);
25762580

@@ -2646,8 +2650,8 @@
26462650
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
26472651
point3 lookfrom, point3 lookat, vec3 vup,
26482652
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
2649-
double vfov, // top to bottom, in degrees
2650-
double aspect
2653+
double vfov, // vertical field-of-view in degrees
2654+
double aspect_ratio
26512655
) {
26522656
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
26532657
origin = lookfrom;
@@ -2656,7 +2660,7 @@
26562660

26572661
auto theta = degrees_to_radians(vfov);
26582662
auto half_height = tan(theta/2);
2659-
auto half_width = aspect * half_height;
2663+
auto half_width = aspect_ratio * half_height;
26602664

26612665
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
26622666
w = unit_vector(lookfrom - lookat);
@@ -2687,8 +2691,6 @@
26872691
This allows us to change the viewpoint:
26882692

26892693
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
2690-
const auto aspect_ratio = double(image_width) / image_height;
2691-
...
26922694
camera cam(point3(-2,2,1), point3(0,0,-1), vup, 90, aspect_ratio);
26932695
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
26942696
[Listing [scene-free-view]: <kbd>[main.cc]</kbd> Scene with alternate viewpoint]
@@ -2781,17 +2783,17 @@
27812783
public:
27822784
camera(
27832785
point3 lookfrom, point3 lookat, vec3 vup,
2784-
double vfov, // top to bottom, in degrees
2786+
double vfov, // vertical field-of-view in degrees
27852787
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
2786-
double aspect, double aperture, double focus_dist
2788+
double aspect_ratio, double aperture, double focus_dist
27872789
) {
27882790
origin = lookfrom;
27892791
lens_radius = aperture / 2;
27902792
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
27912793

27922794
auto theta = degrees_to_radians(vfov);
27932795
auto half_height = tan(theta/2);
2794-
auto half_width = aspect * half_height;
2796+
auto half_width = aspect_ratio * half_height;
27952797

27962798
w = unit_vector(lookfrom - lookat);
27972799
u = unit_vector(cross(vup, w));
@@ -2837,8 +2839,6 @@
28372839
Using a big aperture:
28382840

28392841
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
2840-
const auto aspect_ratio = double(image_width) / image_height;
2841-
...
28422842
point3 lookfrom(3,3,2);
28432843
point3 lookat(0,0,-1);
28442844
vec3 vup(0,1,0);

‎books/RayTracingTheNextWeek.html

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -109,9 +109,10 @@
109109
public:
110110
camera(
111111
point3 lookfrom, point3 lookat, vec3 vup,
112-
double vfov, // top to bottom, in degrees
112+
double vfov, // vertical field-of-view in degrees
113+
double aspect_ratio, double aperture, double focus_dist,
113114
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
114-
double aspect, double aperture, double focus_dist, double t0 = 0, double t1 = 0
115+
double t0 = 0, double t1 = 0
115116
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
116117
) {
117118
origin = lookfrom;

‎src/InOneWeekend/main.cc

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -90,11 +90,11 @@ hittable_list random_scene() {
9090

9191

9292
int main() {
93+
const auto aspect_ratio = 16.0 / 9.0;
9394
const int image_width = 1200;
94-
const int image_height = 800;
95+
const int image_height = static_cast<int>(image_width / aspect_ratio);
9596
const int samples_per_pixel = 10;
9697
const int max_depth = 50;
97-
const auto aspect_ratio = double(image_width) / image_height;
9898

9999
std::cout << "P3\n" << image_width << ' ' << image_height << "\n255\n";
100100

@@ -113,8 +113,8 @@ int main() {
113113
for (int i = 0; i < image_width; ++i) {
114114
color pixel_color;
115115
for (int s = 0; s < samples_per_pixel; ++s) {
116-
auto u = (i + random_double()) / image_width;
117-
auto v = (j + random_double()) / image_height;
116+
auto u = (i + random_double()) / (image_width-1);
117+
auto v = (j + random_double()) / (image_height-1);
118118
ray r = cam.get_ray(u, v);
119119
pixel_color += ray_color(r, world, max_depth);
120120
}

‎src/TheNextWeek/main.cc

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -339,9 +339,9 @@ hittable_list final_scene() {
339339

340340

341341
int main() {
342+
const auto aspect_ratio = 1.0 / 1.0;
342343
const int image_width = 600;
343-
const int image_height = 600;
344-
const auto aspect_ratio = double(image_width) / image_height;
344+
const int image_height = static_cast<int>(image_width / aspect_ratio);
345345

346346
hittable_list world;
347347

@@ -442,8 +442,8 @@ int main() {
442442
for (int i = 0; i < image_width; ++i) {
443443
color pixel_color;
444444
for (int s = 0; s < samples_per_pixel; ++s) {
445-
auto u = (i + random_double()) / image_width;
446-
auto v = (j + random_double()) / image_height;
445+
auto u = (i + random_double()) / (image_width-1);
446+
auto v = (j + random_double()) / (image_height-1);
447447
ray r = cam.get_ray(u, v);
448448
pixel_color += ray_color(r, background, world, max_depth);
449449
}

‎src/TheRestOfYourLife/main.cc

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -100,11 +100,11 @@ hittable_list cornell_box(camera& cam, double aspect) {
100100

101101

102102
int main() {
103+
const auto aspect_ratio = 1.0 / 1.0;
103104
const int image_width = 600;
104-
const int image_height = 600;
105+
const int image_height = static_cast<int>(image_width / aspect_ratio);
105106
const int samples_per_pixel = 100;
106107
const int max_depth = 50;
107-
const auto aspect_ratio = double(image_width) / image_height;
108108

109109
std::cout << "P3\n" << image_width << ' ' << image_height << "\n255\n";
110110

@@ -122,8 +122,8 @@ int main() {
122122
for (int i = 0; i < image_width; ++i) {
123123
color pixel_color;
124124
for (int s = 0; s < samples_per_pixel; ++s) {
125-
auto u = (i + random_double()) / image_width;
126-
auto v = (j + random_double()) / image_height;
125+
auto u = (i + random_double()) / (image_width-1);
126+
auto v = (j + random_double()) / (image_height-1);
127127
ray r = cam.get_ray(u, v);
128128
pixel_color += ray_color(r, background, world, lights, max_depth);
129129
}

‎src/common/camera.h

Lines changed: 4 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -20,8 +20,9 @@ class camera {
2020

2121
camera(
2222
point3 lookfrom, point3 lookat, vec3 vup,
23-
double vfov, // top to bottom, in degrees
24-
double aspect, double aperture, double focus_dist, double t0 = 0, double t1 = 0
23+
double vfov, // vertical field-of-view in degrees
24+
double aspect_ratio, double aperture, double focus_dist,
25+
double t0 = 0, double t1 = 0
2526
) {
2627
origin = lookfrom;
2728
lens_radius = aperture / 2;
@@ -30,7 +31,7 @@ class camera {
3031

3132
auto theta = degrees_to_radians(vfov);
3233
auto half_height = tan(theta/2);
33-
auto half_width = aspect * half_height;
34+
auto half_width = aspect_ratio * half_height;
3435

3536
w = unit_vector(lookfrom - lookat);
3637
u = unit_vector(cross(vup, w));

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