Create obj module for scene objects

src/obj.c

@@ -0,0 +1,29 @@
+#include "obj.h"
+
+#include <math.h>
+
+bool intersect_sphere(obj_params_t params, ray_t ray, hit_t *hit_out)
+{
+	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 c = vec3_dot(disp, disp) - r * r;
+
+	const double discriminant = b * b - 4 * a * c;
+	if (discriminant < 0)
+		return false;
+
+	const double t = (-b - sqrt(discriminant)) / (2.0 * a);
+	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;
+	}
+	return true;
+}