hit_test intersect(ray r, object obj) {
v3 ro = r.origin;
v3 rd = r.direction;
double t;
hit_test ht_out;
switch (obj.tag) {
case SPHERE: {
v3 sc = obj.o.s.center;
double sr = obj.o.s.radius;
v3 A = v3_sub(ro, sc);
double B = v3_dot(A, rd);
double C = v3_dot(A, A) - sr*sr;
double D = B*B - C;
t = -B - sqrt(D);
if (D > 0 && t > 0) {
v3 ray_pos = ray_position(r, t);
ht_out.miss = HIT;
ht_out.t = t;
ht_out.hit_point = ray_pos;
ht_out.surf = \
(*(obj.o.s.surface_color))(obj.o.s.center, ray_pos);
ht_out.shine = obj.o.s.shine;
ht_out.surf_norm = v3_norm(v3_sub(ray_pos, obj.o.s.center));
} else {
ht_out.miss = MISS;
}
break;
}
case POSTER: {
v3 n = v3_expr(0, 0, -1);
double d = obj.o.p.upper_left.z;
t = -(v3_dot(ro, n) + d) / v3_dot(rd, n);
v3 ray_pos = ray_position(r, t);
if (t > 0 && is_on_poster(ray_pos, obj.o.p)) {
ht_out.miss = HIT;
ht_out.t = t;
ht_out.hit_point = ray_pos;
ht_out.surf = \
(*(obj.o.p.surface_color))(obj.o.p.upper_left, ray_pos);
ht_out.shine = obj.o.p.shine;
ht_out.surf_norm = n;
} else {
ht_out.miss = MISS;
}
break;
}
default:
fprintf(stderr, "error in intersect: unrecognized tag\n");
exit(1);
}
return ht_out;
}
hit_test intersect_cylinder (ray r, cylinder c) {
hit_test result;
v3 rp = v3_expr(r.direction.x,0,r.direction.z);
double mp = v3_mag(rp);
v3 np = v3_norm(rp);
double xbar = r.origin.x - c.center.x;
double zbar = r.origin.z - c.center.z;
double a = pow(np.x,2) + pow(np.z,2);
double b = 2 * ( (xbar*np.x) + (zbar*np.z) );
double c1 = pow(xbar,2) + pow(zbar,2) - pow(c.radius,2);
double d = pow(b,2) - (4*a*c1);
result.miss = MISS;
if(d >= 0) {
double t_front = (-b - sqrt(d)) / (2*a);
double t_back = (-b + sqrt(d)) / (2*a);
v3 p_front = ray_position(r, t_front/mp);
v3 p_back = ray_position(r, t_back/mp);
if( (t_front < t_back) &&
(t_front > 0) &&
(p_front.y >= c.center.y) && (on_cylinder(p_front, c))) {
result.miss = HIT;
result.t = (t_front/mp);
result.hit_point = p_front;
result.surf = c.surface_color(c.center, p_front);
result.shine = c.shine;
v3 c2 = v3_expr(c.center.x, p_front.y, c.center.z);
result.surf_norm = v3_norm(v3_sub(p_front,c2));
} else if( (t_back > 0) &&
(p_back.y >= c.center.y) &&
(on_cylinder(p_back, c)) ) {
result.miss = HIT;
result.t = (t_back/mp);
result.hit_point = p_back;
result.surf = c.surface_color(c.center, p_back);
result.shine = c.shine;
v3 c3 = v3_expr(c.center.x, p_back.y, c.center.z);
result.surf_norm = v3_norm(v3_sub(c3,p_back));
}
}
return result;
}
hit_test intersect_poster (ray r, poster p)
{
hit_test result = {0};
v3 ro = r.origin;
v3 rd = r.direction;
v3 n = v3_expr(0, 0, -1);
double d = p.upper_left.z;
double t = -(v3_dot(ro, n) + d) / v3_dot(rd, n);
result.miss = MISS;
v3 intersection = ray_position(r, t);
if (t>0 && within_poster(intersection, p)) {
result.miss = HIT;
result.t = t;
result.hit_point = intersection;
result.surf = p.surface_color(p.upper_left, intersection);
result.shine = p.shine;
result.surf_norm = n;
}
return result;
}