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#ifndef _RAY_RENDER_OBJECT_SPHERE_H
#define _RAY_RENDER_OBJECT_SPHERE_H
#include <math.h>
#include "ray_3f.h"
#include "ray_camera.h"
#include "ray_color.h"
#include "ray_object_sphere.h"
#include "ray_object_type.h"
#include "ray_ray.h"
#include "ray_surface.h"
typedef struct ray_render_object_sphere_t {
ray_object_sphere_t object;
ray_3f_t primary_v;
float primary_dot_vv;
float r2;
float r_inv;
} ray_render_object_sphere_t;
static ray_render_object_sphere_t ray_render_object_sphere_prepare(const ray_object_sphere_t *sphere, const ray_camera_t *camera)
{
ray_render_object_sphere_t prepared = { .object = *sphere };
prepared.primary_v = ray_3f_sub(&sphere->center, &camera->position);
prepared.primary_dot_vv = ray_3f_dot(&prepared.primary_v, &prepared.primary_v);
prepared.r2 = sphere->radius * sphere->radius;
/* to divide by radius via multiplication in ray_object_sphere_normal() */
prepared.r_inv = 1.0f / sphere->radius;
return prepared;
}
static inline int ray_render_object_sphere_intersects_ray(ray_render_object_sphere_t *sphere, unsigned depth, ray_ray_t *ray, float *res_distance)
{
ray_3f_t v = sphere->primary_v;
float dot_vv = sphere->primary_dot_vv;
float b, disc;
if (depth) {
v = ray_3f_sub(&sphere->object.center, &ray->origin);
dot_vv = ray_3f_dot(&v, &v);
}
b = ray_3f_dot(&v, &ray->direction);
disc = sphere->r2 - (dot_vv - (b * b));
if (disc > 0) {
float i1, i2;
disc = sqrtf(disc);
i1 = b - disc;
i2 = b + disc;
if (i2 > 0 && i1 > 0) {
*res_distance = i1;
return 1;
}
}
return 0;
}
/* return the normal of the surface at the specified point */
static inline ray_3f_t ray_render_object_sphere_normal(ray_render_object_sphere_t *sphere, ray_3f_t *point)
{
ray_3f_t normal;
normal = ray_3f_sub(point, &sphere->object.center);
normal = ray_3f_mult_scalar(&normal, sphere->r_inv); /* normalize without the sqrt() */
return normal;
}
/* return the surface of the sphere @ point */
static inline ray_surface_t ray_render_object_sphere_surface(ray_render_object_sphere_t *sphere, ray_3f_t *point)
{
/* uniform solids for now... */
return sphere->object.surface;
}
#endif
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