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Small improvement to rotate_y::hit() function #1617

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Merged
merged 2 commits into from
Aug 23, 2024
Merged

Small improvement to rotate_y::hit() function #1617

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276cf1c
Small improvement to rotate_y::hit() function
hollasch Aug 22, 2024
07f11f5
Merge branch 'dev-patch' into refactor/rotate-y-hit
hollasch Aug 23, 2024
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@ Change Log / Ray Tracing in One Weekend
- Fix -- Big improvement to print version listing font size (#1595) and more compact line
height for code listings in both print and browser.
- Change -- Include hittable.h from material.h; drop `hit_record` forward declaration (#1609)
- Fix -- Slight improvement to `rotate_y::hit()` function (#1484)
- Fix -- Fixed possible bogus values from `random_unit_vector()` due to underflow (#1606)

### In One Weekend
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43 changes: 25 additions & 18 deletions books/RayTracingTheNextWeek.html
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Expand Up @@ -3816,34 +3816,41 @@
public:

bool hit(const ray& r, interval ray_t, hit_record& rec) const override {
// Change the ray from world space to object space
auto origin = r.origin();
auto direction = r.direction();

origin[0] = cos_theta*r.origin()[0] - sin_theta*r.origin()[2];
origin[2] = sin_theta*r.origin()[0] + cos_theta*r.origin()[2];
// Transform the ray from world space to object space.

direction[0] = cos_theta*r.direction()[0] - sin_theta*r.direction()[2];
direction[2] = sin_theta*r.direction()[0] + cos_theta*r.direction()[2];
auto origin = point3(
(cos_theta * r.origin().x()) - (sin_theta * r.origin().z()),
r.origin().y(),
(sin_theta * r.origin().x()) + (cos_theta * r.origin().z())
);

auto direction = vec3(
(cos_theta * r.direction().x()) - (sin_theta * r.direction().z()),
r.direction().y(),
(sin_theta * r.direction().x()) + (cos_theta * r.direction().z())
);

ray rotated_r(origin, direction, r.time());

// Determine whether an intersection exists in object space (and if so, where)
// Determine whether an intersection exists in object space (and if so, where).

if (!object->hit(rotated_r, ray_t, rec))
return false;

// Change the intersection point from object space to world space
auto p = rec.p;
p[0] = cos_theta*rec.p[0] + sin_theta*rec.p[2];
p[2] = -sin_theta*rec.p[0] + cos_theta*rec.p[2];
// Transform the intersection from object space back to world space.
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Before, there was a comment about the intersection and one about the normal. Now the one about the normal is gone. Should that just be integrated into this comment, or did you drop mention of the normal on purpose?

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@hollasch hollasch Aug 23, 2024 •
edited
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I considered the normal to be part of the intersection data (which I why I didn't say "intersection point").

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Thanks for checking.


// Change the normal from object space to world space
auto normal = rec.normal;
normal[0] = cos_theta*rec.normal[0] + sin_theta*rec.normal[2];
normal[2] = -sin_theta*rec.normal[0] + cos_theta*rec.normal[2];
rec.p = point3(
(cos_theta * rec.p.x()) + (sin_theta * rec.p.z()),
rec.p.y(),
(-sin_theta * rec.p.x()) + (cos_theta * rec.p.z())
);

rec.p = p;
rec.normal = normal;
rec.normal = vec3(
(cos_theta * rec.normal.x()) + (sin_theta * rec.normal.z()),
rec.normal.y(),
(-sin_theta * rec.normal.x()) + (cos_theta * rec.normal.z())
);

return true;
}
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43 changes: 25 additions & 18 deletions src/TheNextWeek/hittable.h
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Expand Up @@ -115,34 +115,41 @@ class rotate_y : public hittable {
}

bool hit(const ray& r, interval ray_t, hit_record& rec) const override {
// Change the ray from world space to object space
auto origin = r.origin();
auto direction = r.direction();

origin[0] = cos_theta*r.origin()[0] - sin_theta*r.origin()[2];
origin[2] = sin_theta*r.origin()[0] + cos_theta*r.origin()[2];
// Transform the ray from world space to object space.

direction[0] = cos_theta*r.direction()[0] - sin_theta*r.direction()[2];
direction[2] = sin_theta*r.direction()[0] + cos_theta*r.direction()[2];
auto origin = point3(
(cos_theta * r.origin().x()) - (sin_theta * r.origin().z()),
r.origin().y(),
(sin_theta * r.origin().x()) + (cos_theta * r.origin().z())
);

auto direction = vec3(
(cos_theta * r.direction().x()) - (sin_theta * r.direction().z()),
r.direction().y(),
(sin_theta * r.direction().x()) + (cos_theta * r.direction().z())
);

ray rotated_r(origin, direction, r.time());

// Determine whether an intersection exists in object space (and if so, where)
// Determine whether an intersection exists in object space (and if so, where).

if (!object->hit(rotated_r, ray_t, rec))
return false;

// Change the intersection point from object space to world space
auto p = rec.p;
p[0] = cos_theta*rec.p[0] + sin_theta*rec.p[2];
p[2] = -sin_theta*rec.p[0] + cos_theta*rec.p[2];
// Transform the intersection from object space back to world space.

// Change the normal from object space to world space
auto normal = rec.normal;
normal[0] = cos_theta*rec.normal[0] + sin_theta*rec.normal[2];
normal[2] = -sin_theta*rec.normal[0] + cos_theta*rec.normal[2];
rec.p = point3(
(cos_theta * rec.p.x()) + (sin_theta * rec.p.z()),
rec.p.y(),
(-sin_theta * rec.p.x()) + (cos_theta * rec.p.z())
);

rec.p = p;
rec.normal = normal;
rec.normal = vec3(
(cos_theta * rec.normal.x()) + (sin_theta * rec.normal.z()),
rec.normal.y(),
(-sin_theta * rec.normal.x()) + (cos_theta * rec.normal.z())
);

return true;
}
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43 changes: 25 additions & 18 deletions src/TheRestOfYourLife/hittable.h
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Expand Up @@ -123,34 +123,41 @@ class rotate_y : public hittable {
}

bool hit(const ray& r, interval ray_t, hit_record& rec) const override {
// Change the ray from world space to object space
auto origin = r.origin();
auto direction = r.direction();

origin[0] = cos_theta*r.origin()[0] - sin_theta*r.origin()[2];
origin[2] = sin_theta*r.origin()[0] + cos_theta*r.origin()[2];
// Transform the ray from world space to object space.

direction[0] = cos_theta*r.direction()[0] - sin_theta*r.direction()[2];
direction[2] = sin_theta*r.direction()[0] + cos_theta*r.direction()[2];
auto origin = point3(
(cos_theta * r.origin().x()) - (sin_theta * r.origin().z()),
r.origin().y(),
(sin_theta * r.origin().x()) + (cos_theta * r.origin().z())
);

auto direction = vec3(
(cos_theta * r.direction().x()) - (sin_theta * r.direction().z()),
r.direction().y(),
(sin_theta * r.direction().x()) + (cos_theta * r.direction().z())
);

ray rotated_r(origin, direction, r.time());

// Determine whether an intersection exists in object space (and if so, where)
// Determine whether an intersection exists in object space (and if so, where).

if (!object->hit(rotated_r, ray_t, rec))
return false;

// Change the intersection point from object space to world space
auto p = rec.p;
p[0] = cos_theta*rec.p[0] + sin_theta*rec.p[2];
p[2] = -sin_theta*rec.p[0] + cos_theta*rec.p[2];
// Transform the intersection from object space back to world space.

// Change the normal from object space to world space
auto normal = rec.normal;
normal[0] = cos_theta*rec.normal[0] + sin_theta*rec.normal[2];
normal[2] = -sin_theta*rec.normal[0] + cos_theta*rec.normal[2];
rec.p = point3(
(cos_theta * rec.p.x()) + (sin_theta * rec.p.z()),
rec.p.y(),
(-sin_theta * rec.p.x()) + (cos_theta * rec.p.z())
);

rec.p = p;
rec.normal = normal;
rec.normal = vec3(
(cos_theta * rec.normal.x()) + (sin_theta * rec.normal.z()),
rec.normal.y(),
(-sin_theta * rec.normal.x()) + (cos_theta * rec.normal.z())
);

return true;
}
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