void Rotation(Point2d previous_mouse_coord, Point2d current_mouse_coord) {
// calculation of p
float x_p = static_cast<float>(previous_mouse_coord.x);
x_p = 2*x_p/window_width - 1;
float y_p = static_cast<float>(previous_mouse_coord.y);
y_p = 2*(window_height - y_p)/window_height - 1;
float z_p;
float root_p = (1- pow(x_p, 2) - pow(y_p, 2));
if (root_p < 0) {
// if the point is outside of the unit sphere, then the point lies
// somewhere in the xy plane, so z = 0
z_p = 0;
} else {
z_p = sqrt(1- pow(x_p, 2) - pow(y_p, 2));
}
Vec3f p = {x_p, y_p, z_p};
// calculation of q
float x_q = static_cast<float>(current_mouse_coord.x);
x_q = 2*x_q/window_width - 1;
float y_q = static_cast<float>(current_mouse_coord.y);
y_q = 2*(window_height - y_q)/window_height - 1;
float z_q;
float root_q = (1- pow(x_q, 2) - pow(y_q, 2));
if (root_q < 0) {
z_q = 0;
} else {
z_q = sqrt(1- pow(x_q, 2) - pow(y_q, 2));
}
Vec3f q = {x_q, y_q, z_q};
// calculation of angle with unitary p and q
float angle = acos(p.unit() * q.unit())*180.0/PI;
// if for some reason the angle comes out as NaN, change it to zero
if (angle != angle)
angle = 0;
// calculation of normal
Vec3f origin = {0, 0, 0};
p = p - origin;
Vec3f n = p.crossProduct(q - origin);
// store the this rotation with all previous rotations
glLoadIdentity();
glRotatef(angle, n.x[0], n.x[1], n.x[2]);
glMultMatrixf(current_matrix);
glGetFloatv(GL_MODELVIEW_MATRIX, current_matrix);
}
// [comment]
// The main ray-triangle intersection routine. You can test both methoods: the
// geometric method and the Moller-Trumbore algorithm (use the flag -DMOLLER_TRUMBORE
// when you compile.
// [/comment]
bool rayTriangleIntersect(
const Vec3f &orig, const Vec3f &dir,
const Vec3f &v0, const Vec3f &v1, const Vec3f &v2,
float &t, float &u, float &v)
{
#ifdef MOLLER_TRUMBORE
Vec3f v0v1 = v1 - v0;
Vec3f v0v2 = v2 - v0;
Vec3f pvec = dir.crossProduct(v0v2);
float det = v0v1.dotProduct(pvec);
#ifdef CULLING
// if the determinant is negative the triangle is backfacing
// if the determinant is close to 0, the ray misses the triangle
if (det < kEpsilon) return false;
#else
// ray and triangle are parallel if det is close to 0
if (fabs(det) < kEpsilon) return false;
#endif
float invDet = 1 / det;
Vec3f tvec = orig - v0;
u = tvec.dotProduct(pvec) * invDet;
if (u < 0 || u > 1) return false;
Vec3f qvec = tvec.crossProduct(v0v1);
v = dir.dotProduct(qvec) * invDet;
if (v < 0 || u + v > 1) return false;
t = v0v2.dotProduct(qvec) * invDet;
return true;
#else
// compute plane's normal
Vec3f v0v1 = v1 - v0;
Vec3f v0v2 = v2 - v0;
// no need to normalize
Vec3f N = v0v1.crossProduct(v0v2); // N
float denom = N.dotProduct(N);
// Step 1: finding P
// check if ray and plane are parallel ?
float NdotRayDirection = N.dotProduct(dir);
if (fabs(NdotRayDirection) < kEpsilon) // almost 0
return false; // they are parallel so they don't intersect !
// compute d parameter using equation 2
float d = N.dotProduct(v0);
// compute t (equation 3)
t = (N.dotProduct(orig) + d) / NdotRayDirection;
// check if the triangle is in behind the ray
if (t < 0) return false; // the triangle is behind
// compute the intersection point using equation 1
Vec3f P = orig + t * dir;
// Step 2: inside-outside test
Vec3f C; // vector perpendicular to triangle's plane
// edge 0
Vec3f edge0 = v1 - v0;
Vec3f vp0 = P - v0;
C = edge0.crossProduct(vp0);
if (N.dotProduct(C) < 0) return false; // P is on the right side
// edge 1
Vec3f edge1 = v2 - v1;
Vec3f vp1 = P - v1;
C = edge1.crossProduct(vp1);
if ((u = N.dotProduct(C)) < 0) return false; // P is on the right side
// edge 2
Vec3f edge2 = v0 - v2;
Vec3f vp2 = P - v2;
C = edge2.crossProduct(vp2);
if ((v = N.dotProduct(C)) < 0) return false; // P is on the right side;
u /= denom;
v /= denom;
return true; // this ray hits the triangle
#endif
}
