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Merge pull request RayTracing#774 from RayTracing/sphere-hit-refactor
Refactor sphere hit method to use common code
2 parents 9a2acc5 + 0a0c519 commit dbb27f2

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‎CHANGELOG.md‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -9,6 +9,7 @@ Change Log -- Ray Tracing in One Weekend
99
- Fix: `random_unit_vector()` was incorrect (#697)
1010
- Fix: Synchronize text and copies of `hittable.h`
1111
- Fix: Synchronize copies of `hittable_list.h`, `material.h`, `sphere.h`
12+
- Change: refactor `sphere::hit()` method to reuse common blocks of code.
1213

1314
### In One Weekend
1415
- Change: Wrote brief explanation waving away negative t values in initial normal sphere

‎books/RayTracingInOneWeekend.html‎

Lines changed: 30 additions & 77 deletions
Original file line numberDiff line numberDiff line change
@@ -902,31 +902,25 @@
902902
auto a = r.direction().length_squared();
903903
auto half_b = dot(oc, r.direction());
904904
auto c = oc.length_squared() - radius*radius;
905-
auto discriminant = half_b*half_b - a*c;
906-
907-
if (discriminant > 0) {
908-
auto root = sqrt(discriminant);
909-
910-
auto temp = (-half_b - root) / a;
911-
if (temp < t_max && temp > t_min) {
912-
rec.t = temp;
913-
rec.p = r.at(rec.t);
914-
rec.normal = (rec.p - center) / radius;
915-
return true;
916-
}
917905

918-
temp = (-half_b + root) / a;
919-
if (temp < t_max && temp > t_min) {
920-
rec.t = temp;
921-
rec.p = r.at(rec.t);
922-
rec.normal = (rec.p - center) / radius;
923-
return true;
924-
}
906+
auto discriminant = half_b*half_b - a*c;
907+
if (discriminant < 0) return false;
908+
auto sqrtd = sqrt(discriminant);
909+
910+
// Find the nearest root that lies in the acceptable range.
911+
auto root = (-half_b - sqrtd) / a;
912+
if (root < t_min || t_max < root) {
913+
root = (-half_b + sqrtd) / a;
914+
if (root < t_min || t_max < root)
915+
return false;
925916
}
926917

927-
return false;
928-
}
918+
rec.t = root;
919+
rec.p = r.at(rec.t);
920+
rec.normal = (rec.p - center) / radius;
929921

922+
return true;
923+
}
930924

931925
#endif
932926
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -1026,36 +1020,16 @@
10261020

10271021
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
10281022
bool sphere::hit(const ray& r, double t_min, double t_max, hit_record& rec) const {
1029-
vec3 oc = r.origin() - center;
1030-
auto a = r.direction().length_squared();
1031-
auto half_b = dot(oc, r.direction());
1032-
auto c = oc.length_squared() - radius*radius;
1033-
auto discriminant = half_b*half_b - a*c;
1023+
...
10341024

1035-
if (discriminant > 0) {
1036-
auto root = sqrt(discriminant);
1037-
auto temp = (-half_b - root) / a;
1038-
if (temp < t_max && temp > t_min) {
1039-
rec.t = temp;
1040-
rec.p = r.at(rec.t);
1041-
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
1042-
vec3 outward_normal = (rec.p - center) / radius;
1043-
rec.set_face_normal(r, outward_normal);
1044-
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
1045-
return true;
1046-
}
1047-
temp = (-half_b + root) / a;
1048-
if (temp < t_max && temp > t_min) {
1049-
rec.t = temp;
1050-
rec.p = r.at(rec.t);
1025+
rec.t = root;
1026+
rec.p = r.at(rec.t);
10511027
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
1052-
vec3 outward_normal = (rec.p - center) / radius;
1053-
rec.set_face_normal(r, outward_normal);
1028+
vec3 outward_normal = (rec.p - center) / radius;
1029+
rec.set_face_normal(r, outward_normal);
10541030
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
1055-
return true;
1056-
}
1057-
}
1058-
return false;
1031+
1032+
return true;
10591033
}
10601034
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
10611035
[Listing [sphere-final]: <kbd>[sphere.h]</kbd> The sphere class with normal determination]
@@ -2013,38 +1987,17 @@
20131987
};
20141988

20151989
bool sphere::hit(const ray& r, double t_min, double t_max, hit_record& rec) const {
2016-
vec3 oc = r.origin() - center;
2017-
auto a = r.direction().length_squared();
2018-
auto half_b = dot(oc, r.direction());
2019-
auto c = oc.length_squared() - radius*radius;
2020-
auto discriminant = half_b*half_b - a*c;
1990+
...
20211991

2022-
if (discriminant > 0) {
2023-
auto root = sqrt(discriminant);
2024-
auto temp = (-half_b - root) / a;
2025-
if (temp < t_max && temp > t_min) {
2026-
rec.t = temp;
2027-
rec.p = r.at(rec.t);
2028-
vec3 outward_normal = (rec.p - center) / radius;
2029-
rec.set_face_normal(r, outward_normal);
2030-
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
2031-
rec.mat_ptr = mat_ptr;
2032-
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
2033-
return true;
2034-
}
2035-
temp = (-half_b + root) / a;
2036-
if (temp < t_max && temp > t_min) {
2037-
rec.t = temp;
2038-
rec.p = r.at(rec.t);
2039-
vec3 outward_normal = (rec.p - center) / radius;
2040-
rec.set_face_normal(r, outward_normal);
1992+
rec.t = root;
1993+
rec.p = r.at(rec.t);
1994+
vec3 outward_normal = (rec.p - center) / radius;
1995+
rec.set_face_normal(r, outward_normal);
20411996
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
2042-
rec.mat_ptr = mat_ptr;
1997+
rec.mat_ptr = mat_ptr;
20431998
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
2044-
return true;
2045-
}
2046-
}
2047-
return false;
1999+
2000+
return true;
20482001
}
20492002
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
20502003
[Listing [sphere-material]: <kbd>[sphere.h]</kbd> Ray-sphere intersection with added material information]

‎books/RayTracingTheNextWeek.html‎

Lines changed: 25 additions & 54 deletions
Original file line numberDiff line numberDiff line change
@@ -222,9 +222,7 @@
222222
just needs to become a function `center(time)`:
223223

224224
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
225-
bool moving_sphere::hit(
226-
const ray& r, double t_min, double t_max, hit_record& rec) const {
227-
225+
bool moving_sphere::hit(const ray& r, double t_min, double t_max, hit_record& rec) const {
228226
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
229227
vec3 oc = r.origin() - center(r.time());
230228
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
@@ -233,35 +231,26 @@
233231
auto c = oc.length_squared() - radius*radius;
234232

235233
auto discriminant = half_b*half_b - a*c;
234+
if (discriminant < 0) return false;
235+
auto sqrtd = sqrt(discriminant);
236+
237+
// Find the nearest root that lies in the acceptable range.
238+
auto root = (-half_b - sqrtd) / a;
239+
if (root < t_min || t_max < root) {
240+
root = (-half_b + sqrtd) / a;
241+
if (root < t_min || t_max < root)
242+
return false;
243+
}
236244

237-
if (discriminant > 0) {
238-
auto root = sqrt(discriminant);
239-
240-
auto temp = (-half_b - root) / a;
241-
if (temp < t_max && temp > t_min) {
242-
rec.t = temp;
243-
rec.p = r.at(rec.t);
245+
rec.t = root;
246+
rec.p = r.at(rec.t);
244247
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
245-
auto outward_normal = (rec.p - center(r.time())) / radius;
248+
auto outward_normal = (rec.p - center(r.time())) / radius;
246249
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
247-
rec.set_face_normal(r, outward_normal);
248-
rec.mat_ptr = mat_ptr;
249-
return true;
250-
}
250+
rec.set_face_normal(r, outward_normal);
251+
rec.mat_ptr = mat_ptr;
251252

252-
temp = (-half_b + root) / a;
253-
if (temp < t_max && temp > t_min) {
254-
rec.t = temp;
255-
rec.p = r.at(rec.t);
256-
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
257-
auto outward_normal = (rec.p - center(r.time())) / radius;
258-
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
259-
rec.set_face_normal(r, outward_normal);
260-
rec.mat_ptr = mat_ptr;
261-
return true;
262-
}
263-
}
264-
return false;
253+
return true;
265254
}
266255
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
267256
[Listing [moving-sphere-hit]: <kbd>[moving_sphere.h]</kbd> Moving sphere hit function]
@@ -1202,38 +1191,20 @@
12021191
Update the `sphere::hit()` function to use this function to update the hit record UV coordinates.
12031192

12041193
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
1205-
...
12061194
bool sphere::hit(...) {
12071195
...
1208-
if (discriminant > 0) {
1209-
...
1210-
temp = (-half_b - root) / a;
1211-
if (temp < t_max && temp > t_min) {
1212-
rec.t = temp;
1213-
rec.p = r.at(rec.t);
1214-
vec3 outward_normal = (rec.p - center) / radius;
1215-
rec.set_face_normal(r, outward_normal);
1216-
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
1217-
get_sphere_uv((rec.p-center)/radius, rec.u, rec.v);
1218-
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
1219-
rec.mat_ptr = mat_ptr;
1220-
return true;
1221-
}
12221196

1223-
temp = (-half_b + root) / a;
1224-
if (temp < t_max && temp > t_min) {
1225-
rec.t = temp;
1226-
rec.p = r.at(rec.t);
1227-
vec3 outward_normal = (rec.p - center) / radius;
1228-
rec.set_face_normal(r, outward_normal);
1197+
rec.t = root;
1198+
rec.p = r.at(rec.t);
1199+
vec3 outward_normal = (rec.p - center) / radius;
1200+
rec.set_face_normal(r, outward_normal);
12291201
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++ highlight
1230-
get_sphere_uv((rec.p-center)/radius, rec.u, rec.v);
1202+
get_sphere_uv(outward_normal, rec.u, rec.v);
12311203
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ C++
1232-
rec.mat_ptr = mat_ptr;
1233-
return true;
1234-
}
1235-
...
1204+
rec.mat_ptr = mat_ptr;
12361205

1206+
return true;
1207+
}
12371208
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
12381209
[Listing [get-sphere-uv-call]: <kbd>[sphere.h]</kbd> Sphere UV coordinates from hit]
12391210
</div>

‎src/InOneWeekend/sphere.h‎

Lines changed: 16 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -38,33 +38,26 @@ bool sphere::hit(const ray& r, double t_min, double t_max, hit_record& rec) cons
3838
auto a = r.direction().length_squared();
3939
auto half_b = dot(oc, r.direction());
4040
auto c = oc.length_squared() - radius*radius;
41-
auto discriminant = half_b*half_b - a*c;
42-
43-
if (discriminant > 0) {
44-
auto root = sqrt(discriminant);
4541

46-
auto temp = (-half_b - root) / a;
47-
if (temp < t_max && temp > t_min) {
48-
rec.t = temp;
49-
rec.p = r.at(rec.t);
50-
vec3 outward_normal = (rec.p - center) / radius;
51-
rec.set_face_normal(r, outward_normal);
52-
rec.mat_ptr = mat_ptr;
53-
return true;
54-
}
42+
auto discriminant = half_b*half_b - a*c;
43+
if (discriminant < 0) return false;
44+
auto sqrtd = sqrt(discriminant);
5545

56-
temp = (-half_b + root) / a;
57-
if (temp < t_max && temp > t_min) {
58-
rec.t = temp;
59-
rec.p = r.at(rec.t);
60-
vec3 outward_normal = (rec.p - center) / radius;
61-
rec.set_face_normal(r, outward_normal);
62-
rec.mat_ptr = mat_ptr;
63-
return true;
64-
}
46+
// Find the nearest root that lies in the acceptable range.
47+
auto root = (-half_b - sqrtd) / a;
48+
if (root < t_min || t_max < root) {
49+
root = (-half_b + sqrtd) / a;
50+
if (root < t_min || t_max < root)
51+
return false;
6552
}
6653

67-
return false;
54+
rec.t = root;
55+
rec.p = r.at(rec.t);
56+
vec3 outward_normal = (rec.p - center) / radius;
57+
rec.set_face_normal(r, outward_normal);
58+
rec.mat_ptr = mat_ptr;
59+
60+
return true;
6861
}
6962

7063

‎src/TheNextWeek/moving_sphere.h‎

Lines changed: 16 additions & 25 deletions
Original file line numberDiff line numberDiff line change
@@ -56,40 +56,31 @@ bool moving_sphere::bounding_box(double _time0, double _time1, aabb& output_box)
5656
}
5757

5858

59-
// replace "center" with "center(r.time())"
6059
bool moving_sphere::hit(const ray& r, double t_min, double t_max, hit_record& rec) const {
6160
vec3 oc = r.origin() - center(r.time());
6261
auto a = r.direction().length_squared();
6362
auto half_b = dot(oc, r.direction());
6463
auto c = oc.length_squared() - radius*radius;
6564

6665
auto discriminant = half_b*half_b - a*c;
67-
68-
if (discriminant > 0) {
69-
auto root = sqrt(discriminant);
70-
71-
auto temp = (-half_b - root)/a;
72-
if (temp < t_max && temp > t_min) {
73-
rec.t = temp;
74-
rec.p = r.at(rec.t);
75-
vec3 outward_normal = (rec.p - center(r.time())) / radius;
76-
rec.set_face_normal(r, outward_normal);
77-
rec.mat_ptr = mat_ptr;
78-
return true;
79-
}
80-
81-
temp = (-half_b + root)/a;
82-
if (temp < t_max && temp > t_min) {
83-
rec.t = temp;
84-
rec.p = r.at(rec.t);
85-
vec3 outward_normal = (rec.p - center(r.time())) / radius;
86-
rec.set_face_normal(r, outward_normal);
87-
rec.mat_ptr = mat_ptr;
88-
return true;
89-
}
66+
if (discriminant < 0) return false;
67+
auto sqrtd = sqrt(discriminant);
68+
69+
// Find the nearest root that lies in the acceptable range.
70+
auto root = (-half_b - sqrtd) / a;
71+
if (root < t_min || t_max < root) {
72+
root = (-half_b + sqrtd) / a;
73+
if (root < t_min || t_max < root)
74+
return false;
9075
}
9176

92-
return false;
77+
rec.t = root;
78+
rec.p = r.at(rec.t);
79+
vec3 outward_normal = (rec.p - center(r.time())) / radius;
80+
rec.set_face_normal(r, outward_normal);
81+
rec.mat_ptr = mat_ptr;
82+
83+
return true;
9384
}
9485

9586
#endif

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