//returns a random integer in [from, to]
static int get_rand_int_range(MContext *mc, int from, int to) {
assert(to >= from);
next_rand(mc);
int range = (to - from) + 1;
int small_rand = mc->rand % range; //ok for small ranges
return from + small_rand;
}
void Snake::action()
{
int r = next_rand(4);
if (r == 0)
go_random();
else if (r == 1)
fight(random_actor());
}
Vec trace(const Ray& r, const int index, const int num_samps) {
// ray-sphere intersection
double t;
if (!intersect(r, t)) return Vec();
// compute the intersection data
const Vec x = r.o + r.d * t, n = (x - sph.p).normalized(), w = -r.d;
// compute Fresnel transmittance at point of emergence
const double T21 = 1.0 - fresnel(w.dot(n), eta);
// integration of the BSSRDF over the surface
unsigned int xi = next_rand(index);
Vec result;
for (int i = 0; i < num_samps; i++) {
// generate a sample
Vec sp, sn, sw;
sample(i, Vec(hal(2, index), hal(3, index), 0.0), sp, sn);
sw = Vec(1, 1, -0.5).normalized();
// directional light source
const double radiance = 8.0*PI;
const double cos_wi_n = sn.dot(sw);
if (cos_wi_n > 0.0) {
// Russian roulette (note that accept_prob can be any value in (0, 1))
const double accept_prob = exp(-(sp - x).len() * min_sigma_tr);
if ((xi / rand_range) < accept_prob) {
const double T12 = 1.0 - fresnel(cos_wi_n, eta);
const double Li_cos = T12 * radiance * cos_wi_n / (samplePDF * accept_prob);
for (int j = 0; j < 3; j++) result[j] += bssrdf(sp, sn, sw, x, n, w, j) * Li_cos;
// reciprocal evaulation with the reciprocity hack
//for (int j = 0; j < 3; j++) result[j] += 0.5 * (bssrdf(sp, sn, sw, x, n, w, j) + bssrdf(x, n, w, sp, sn, sw, j)) * Li_cos;
}
xi = next_rand(xi);
}
}
return T21 * result / (double)num_samps;
}
void fh_embed_to_signal(complex *freq_buffer, int f_buffer_len)
{ //{{{
if(embed_iteration >= 4 && embed_iteration <= 5 || embed_iteration == 0)
printf("embed %d orig: ", embed_iteration); print_pow_density(freq_buffer, 10);
char *message = wmark->message;
int next_r = 0;
for(int i = 0; i < wmark->len; i++){
next_r = next_rand(i);
complex old_freq_elt = freq_buffer[next_r];
watermark_elt(c_to_d(message[i]), &(freq_buffer[next_r]));
if(embed_iteration >= 4 && embed_iteration <= 5 || embed_iteration == 0){
printf("embed %d %c, %1.4f+%1.4fi => %1.4f+%1.4fi : %d : %f\n",
embed_iteration, message[i],
creal(old_freq_elt), cimag(old_freq_elt),
creal(freq_buffer[next_r]), cimag(freq_buffer[next_r]),
next_r, c_to_d(message[i]));
}
}
} //}}}
