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Add front/back face detection

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Camden Dixie O'Brien
2025-09-23 15:36:08 +01:00
parent f4ffea57fd
commit 9bf8753f42
3 changed files with 26 additions and 12 deletions
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24
src/obj.c
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@@ -2,28 +2,34 @@
#include <math.h>
bool intersect_sphere(obj_params_t params, ray_t ray, hit_t *hit_out)
bool intersect_sphere(
obj_params_t params, ray_t ray, hit_t *hit_out, double t_min,
double t_max)
{
const vec3_t centre = params.sphere.centre;
const double r = params.sphere.radius;
const vec3_t disp = vec3_sub(centre, ray.orig);
const double a = vec3_dot(ray.dir, ray.dir);
const double b = -2.0 * vec3_dot(ray.dir, disp);
const double h = vec3_dot(ray.dir, disp);
const double c = vec3_dot(disp, disp) - r * r;
const double discriminant = b * b - 4 * a * c;
const double discriminant = h * h - a * c;
if (discriminant < 0)
return false;
const double t = (-b - sqrt(discriminant)) / (2.0 * a);
const double sqrtd = sqrt(discriminant);
const double low = (h - sqrtd) / a;
const double t = low > t_min ? low : (h + sqrtd) / a;
if (t < t_min || t_max < t)
return false;
const vec3_t point = vec3_add(ray.orig, vec3_scale(ray.dir, t));
const vec3_t normal = vec3_unit(vec3_sub(point, centre));
if (hit_out != nullptr) {
hit_out->point = point;
hit_out->normal = normal;
hit_out->t = t;
}
hit_out->point = point;
hit_out->normal = normal;
hit_out->t = t;
hit_out->front = vec3_dot(ray.dir, normal) < 0.0;
return true;
}