89 lines
2.7 KiB
C
89 lines
2.7 KiB
C
#include "hittable.h"
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#include "point3.h"
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#include "vec3.h"
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#include <math.h>
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#include <stdlib.h>
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#include <string.h>
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void hit_record_set_face_normal(HitRecord *record, Ray r, Vec3 outward_normal) {
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record->front_face = vec3_dot(r.direction, outward_normal) < 0;
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record->normal =
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record->front_face ? outward_normal : vec3_neg(outward_normal);
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}
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bool hittable_hit(const Hittable *hittable, Ray r, double t_min, double t_max,
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HitRecord *record) {
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switch (hittable->type) {
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case HITTABLE_LIST:
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return hittable_list_hit((const HittableList *)hittable, r, t_min, t_max,
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record);
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case HITTABLE_SPHERE:
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return sphere_hit((const Sphere *)hittable, r, t_min, t_max, record);
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}
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return false;
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}
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static void hittable_list_grow(HittableList *list, size_t n, Arena *arena) {
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if (list->objects) {
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const Hittable **new_objects =
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arena_alloc(arena, (list->capacity + n) * sizeof(Hittable *));
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memcpy(new_objects, list->objects, list->size * sizeof(Hittable *));
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list->objects = new_objects;
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list->capacity += n;
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} else {
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list->objects = arena_alloc(arena, n * sizeof(Hittable *));
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list->capacity = n;
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list->size = 0;
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}
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}
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void hittable_list_add(HittableList *list, const Hittable *hittable,
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Arena *arena) {
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if (list->capacity == list->size)
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hittable_list_grow(list, list->capacity == 0 ? 16 : list->capacity, arena);
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list->objects[list->size++] = hittable;
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}
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bool hittable_list_hit(const HittableList *list, Ray r, double t_min,
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double t_max, HitRecord *record) {
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bool hit_anything = false;
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double closest_so_far = t_max;
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for (size_t i = 0; i < list->size; ++i) {
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if (hittable_hit(list->objects[i], r, t_min, closest_so_far, record)) {
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hit_anything = true;
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closest_so_far = record->t;
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}
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}
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return hit_anything;
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}
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bool sphere_hit(const Sphere *sphere, Ray r, double t_min, double t_max,
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HitRecord *record) {
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Vec3 oc = point3_sub(r.origin, sphere->center);
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double a = vec3_length2(r.direction);
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double half_b = vec3_dot(oc, r.direction);
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double c = vec3_length2(oc) - sphere->radius * sphere->radius;
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double discriminant = half_b * half_b - a * c;
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if (discriminant < 0)
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return false;
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double square_root = sqrt(discriminant);
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double root = (-half_b - square_root) / a;
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if (root < t_min || t_max < root) {
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root = (-half_b + square_root) / a;
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if (root < t_min || t_max < root)
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return false;
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}
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record->t = root;
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record->p = ray_at(r, root);
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Vec3 outward_normal =
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vec3_div(point3_sub(record->p, sphere->center), sphere->radius);
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hit_record_set_face_normal(record, r, outward_normal);
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record->material = sphere->material;
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return true;
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}
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