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old intersect.txt
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old intersect.txt
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int perm_sign(int n, int p[]){
int p_[n];
for(int i = 0; i < n; i++)
p_[i] = p[i];
int p_sign = 1;
for(int i = 0; i < n; i++){
for(int j = i; j < n; j++){
if(p_[j] == i){
if(j != i){
swap(p_[j], p_[i]);
p_sign *= -1;
}
break;
}
}
}
return p_sign;
}
bool intersect(simplex &s, ray r, vec3 &p){
double det = 0.0, delta_det = 0.0;
int perm[] = {0, 1, 2, 3};
do{
int p_sign = perm_sign(4, perm);
double d1 = 1.0, d2 = 1.0;
for(int i = 0; i < 3; i++){
d1 *= s.p[i].c[perm[i]];
d2 *= s.p[i].c[perm[i]];
}
d1 *= r.starting_point.c[perm[3]];
if(perm[3] == 3)d2 = 0;
else d2 *= r.direction.c[perm[3]];
det += p_sign * d1;
delta_det += p_sign * d2;
}while(next_permutation(perm, perm + 4));
if(fabs(det) < eps)return false;
if(fabs(delta_det) < eps)return false;
if(det / delta_det > eps)return false;
p = r.starting_point - (det / delta_det) * r.direction;
int gsign = 0;
for(int i = 0; i < 3; i++){
double c = dot(r.direction, cross(s.p[i] - r.starting_point, s.p[(i + 1) % 3] - r.starting_point));
int csign = 0;
if(c < -eps)csign = -1;
if(c > eps)csign = 1;
if(csign == 0)continue;
else if(gsign == 0)gsign = csign;
else if(gsign != csign)return false;
}
return true;
}