ao_intersect.cpp

#include "ao.h"

void
ray_sphere_intersect(Isect *isect, const Ray *ray, const Sphere *sphere)
{
    vec rs;

    rs.x = ray->org.x - sphere->center.x;
    rs.y = ray->org.y - sphere->center.y;
    rs.z = ray->org.z - sphere->center.z;

    double B = vdot(rs, ray->dir);
    double C = vdot(rs, rs) - sphere->radius * sphere->radius;
    double D = B * B - C;

    if (D > 0.0) {
        double t = -B - sqrt(D);
        
        if ((t > 0.0) && (t < isect->t)) {
            isect->t = t;
            isect->hit = 1;
            
            isect->p.x = ray->org.x + ray->dir.x * t;
            isect->p.y = ray->org.y + ray->dir.y * t;
            isect->p.z = ray->org.z + ray->dir.z * t;

            isect->n.x = isect->p.x - sphere->center.x;
            isect->n.y = isect->p.y - sphere->center.y;
            isect->n.z = isect->p.z - sphere->center.z;

            vnormalize(&(isect->n));
        }
    }
}

void
ray_plane_intersect(Isect *isect, const Ray *ray, const Plane *plane)
{
    double d = -vdot(plane->p, plane->n);
    double v = vdot(ray->dir, plane->n);

    if (fabs(v) < 1.0e-17) return;

    double t = -(vdot(ray->org, plane->n) + d) / v;

    if ((t > 0.0) && (t < isect->t)) {
        isect->t = t;
        isect->hit = 1;
        
        isect->p.x = ray->org.x + ray->dir.x * t;
        isect->p.y = ray->org.y + ray->dir.y * t;
        isect->p.z = ray->org.z + ray->dir.z * t;

        isect->n = plane->n;
    }
}