OBox OBox::box_triangle(const Triangle& t)
{
Vec3f e0 = t.get_v1()-t.get_v0();
Vec3f e1 = t.get_v2()-t.get_v1();
Vec3f e2 = t.get_v0()-t.get_v2();
Vec3f X,Y,Z;
if(sqr_length(e0) > sqr_length(e1))
{
if(sqr_length(e0) > sqr_length(e2))
{
X = normalize(e0);
Y = normalize(e1 - X * dot(X, e1));
}
else
{
X = normalize(e2);
Y = normalize(e0 - X * dot(X, e0));
}
}
else
{
if(sqr_length(e1) > sqr_length(e2))
{
X = normalize(e1);
Y = normalize(e2 - X * dot(X, e2));
}
else
{
X = normalize(e2);
Y = normalize(e0 - X * dot(X, e0));
}
}
Z = cross(X,Y);
const Mat3x3f Rot(X,Y,Z);
Vec3f p0 = Rot * t.get_v0();
Vec3f p1 = Rot * t.get_v1();
Vec3f p2 = Rot * t.get_v2();
Vec3f pmin = v_min(p0, v_min(p1, p2));
Vec3f pmax = v_max(p0, v_max(p1, p2));
Vec3f centre_close = v_max(pmin, v_min(pmax, Rot * t.get_centre()));
return OBox(Rot, AABox(pmin, pmax, centre_close));
}
OBox OBox::box_and_split(const std::vector<Triangle>& invec,
std::vector<Triangle>& lvec,
std::vector<Triangle>& rvec)
{
// Obtain the rotation matrix for the OBB
const Mat3x3f Rot = compute_rotation(invec);
const int N_tri = invec.size();
const int N_pts = 3*N_tri;
// Compute the rotated set of points and the extents of the point aligned
// BBox.
vector<Vec3f> pts(N_pts);
Vec3f tri_pmin(FLT_MAX), tri_pmax(-FLT_MAX);
for(int i=0;i<N_tri;++i)
{
const Triangle& tri = invec[i];
int offs = 3*i;
pts[offs ] = Rot*tri.get_v0();
pts[offs+1] = Rot*tri.get_v1();
pts[offs+2] = Rot*tri.get_v2();
for(int j=0;j<3;++j)
{
tri_pmin = v_min(pts[offs+j], tri_pmin);
tri_pmax = v_max(pts[offs+j], tri_pmax);
}
}
// Find the point closest to the centre.
const Vec3f centre = tri_pmin + 0.5f*(tri_pmax-tri_pmin);
Vec3f centre_close;
float min_dist = FLT_MAX;
for(int i=0;i<N_pts;++i)
{
Vec3f v = pts[i];
float sl = sqr_length(centre-v);
if(sl < min_dist)
{
min_dist = sl;
centre_close = v;
}
}
// Partition the triangles
const float thresh = centre[0];
for(int i=0;i<N_tri;++i)
{
Vec3f p = Rot * invec[i].get_centre();
if( p[0] > thresh)
rvec.push_back(invec[i]);
else
lvec.push_back(invec[i]);
}
// If all triangles landed in one box, split them naively.
if(lvec.empty() || rvec.empty())
{
lvec.clear();
lvec.insert(lvec.end(),
invec.begin(),
invec.begin()+N_tri/2);
rvec.clear();
rvec.insert(rvec.end(),
invec.begin()+N_tri/2,
invec.end());
}
return OBox(Rot, AABox(tri_pmin, tri_pmax, centre_close));
}
OBox transform(const OBox& _box, const Quaternion& _rotation, const Vec3& _translation) noexcept
{
return OBox(transform(_box.center, _rotation) + _translation,
_box.halfSides, _box.orientation * _rotation);
}
OBox transform(const OBox& _box, const Vec3& _translation) noexcept
{
return OBox(_box.center + _translation, _box.halfSides, _box.orientation);
}
