void setup_lookat_transform(Transform M, Vect eye, Vect center, Vect up)
{
Vect n, u, v, t;
int i;
// rotational components
VectSub(eye, center, n);
// u = up x n
VectCross(up, n, u);
// v = n x u
VectCross(n, u, v);
// normalize n, u, v
VectUnit(n);
VectUnit(u);
VectUnit(v);
// translation
t[X] = -VectDotProd(eye, u);
t[Y] = -VectDotProd(eye, v);
t[Z] = -VectDotProd(eye, n);
// put it together
for (i = 0; i < 3; i++)
MATRC(M, 0, i) = u[i];
for (i = 0; i < 3; i++)
MATRC(M, 1, i) = v[i];
for (i = 0; i < 3; i++)
MATRC(M, 2, i) = n[i];
for (i = 0; i < 3; i++)
MATRC(M, 3, i) = 0;
for (i = 0; i < 3; i++)
MATRC(M, i, 3) = t[i];
MATRC(M, 3, 3) = 1;
// printf("lookat M = \n");
// TransformPrint(M);
}
Intersection *intersect_ray_triangle(Ray *ray, Vect V0, Vect V1, Vect V2)
{
Vect u, v, n; // triangle vectors
Vect w0, w; // ray vectors
float a, b; // params to calc ray-plane intersect
float t;
Vect I;
Intersection *inter;
// get triangle edge vectors and plane normal
VectSub(V1, V0, u);
VectSub(V2, V0, v);
VectCross(u, v, n);
if (n[X] == 0 && n[Y] == 0 && n[Z] == 0) // triangle is degenerate; do not deal with this case
return NULL;
VectSub(ray->orig, V0, w0);
a = -VectDotProd(n,w0);
b = VectDotProd(n,ray->dir);
if (fabs(b) < SMALL_NUM) { // ray is parallel to triangle plane
if (a == 0) // case 1: ray lies in triangle plane
return NULL;
else return NULL; // case 2: ray disjoint from plane
}
// get intersect point of ray with triangle plane
t = a / b;
if (t < rayeps) // triangle is behind/too close to ray => no intersect
return NULL; // for a segment, also test if (t > 1.0) => no intersect
// intersect point of ray and plane
VectAddS(t, ray->dir, ray->orig, I);
// is I inside T?
float uu, uv, vv, wu, wv, D;
uu = VectDotProd(u,u);
uv = VectDotProd(u,v);
vv = VectDotProd(v,v);
VectSub(I, V0, w);
wu = VectDotProd(w,u);
wv = VectDotProd(w,v);
D = uv * uv - uu * vv;
// get and test parametric (i.e., barycentric) coords
float p, q; // were s, t in original code
p = (uv * wv - vv * wu) / D;
if (p < 0.0 || p > 1.0) // I is outside T
return NULL;
q = (uv * wu - uu * wv) / D;
if (q < 0.0 || (p + q) > 1.0) // I is outside T
return NULL;
inter = make_intersection();
inter->t = t;
VectCopy(inter->P, I);
return inter; // I is in T
}
Intersection *intersect_ray_triangle(Ray *ray, Vect V0, Vect V1, Vect V2)
{
//Vect u, v, n; // triangle vectors
//Vect w0, w; // ray vectors
//float a, b; // params to calc ray-plane intersect
//float t;
//Vect I;
//Intersection *inter;
//// get triangle edge vectors and plane normal
//VectSub(V1, V0, u);
//VectSub(V2, V0, v);
//VectCross(u, v, n);
//if (n[X] == 0 && n[Y] == 0 && n[Z] == 0) // triangle is degenerate; do not deal with this case
// return NULL;
//VectSub(ray->orig, V0, w0);
//a = -VectDotProd(n, w0);
//b = VectDotProd(n, ray->dir);
//if (fabs(b) < SMALL_NUM) { // ray is parallel to triangle plane
// if (a == 0) // case 1: ray lies in triangle plane
// return NULL;
// else return NULL; // case 2: ray disjoint from plane
//}
//// get intersect point of ray with triangle plane
//t = a / b;
//if (t < rayeps) // triangle is behind/too close to ray => no intersect
// return NULL; // for a segment, also test if (t > 1.0) => no intersect
// // intersect point of ray and plane
//VectAddS(t, ray->dir, ray->orig, I);
//// is I inside T?
//float uu, uv, vv, wu, wv, D;
//uu = VectDotProd(u, u);
//uv = VectDotProd(u, v);
//vv = VectDotProd(v, v);
//VectSub(I, V0, w);
//wu = VectDotProd(w, u);
//wv = VectDotProd(w, v);
//D = uv * uv - uu * vv;
//// get and test parametric (i.e., barycentric) coords
//float p, q; // were s, t in original code
//p = (uv * wv - vv * wu) / D;
//if (p < 0.0 || p > 1.0) // I is outside T
// return NULL;
//q = (uv * wu - uu * wv) / D;
//if (q < 0.0 || (p + q) > 1.0) // I is outside T
// return NULL;
//inter = make_intersection();
//inter->t = t;
//VectCopy(inter->P, I);
//return inter; // I is in T
Vect e1, e2, T, P, Q;
double det, t, u1, v1;
VectSub(V1, V0, e1);
VectSub(V2, V0, e2);
VectSub(ray->orig, V0, T);
VectCross(ray->dir, e2, P);
det = VectDotProd(P, e1);
if (det < 0.0f)
{
VectNegate(T, T);
det = -det;
}
// ray parallel to triangle plane
if (det < SMALL_NUM)
return NULL;
u1 = VectDotProd(P, T);
if (u1 < 0.0f || u1 > det)
return NULL;
VectCross(T, e1, Q);
v1 = VectDotProd(Q, ray->dir);
if (v1 < SMALL_NUM || v1 + u1 > det)
return NULL;
t = VectDotProd(Q, e2);
if (t < 0.0f)
return NULL;
t /= det;
Intersection* inter = make_intersection();
VectAddS(t, ray->dir, ray->orig, inter->P);
inter->t = t;
return inter;
}