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quaterion: orthogonalise up before use in look

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This commit is contained in:
Danny Robson 2016-10-17 18:56:10 +11:00
parent 607aaceb29
commit 1582af98e6
1 changed files with 15 additions and 12 deletions
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27
quaternion.cpp
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@ -194,6 +194,8 @@ template util::vector3d util::rotate (util::vector3d, util::quaterniond);
/////////////////////////////////////////////////////////////////////////////// ///////////////////////////////////////////////////////////////////////////////
// based on the implementation at:
// http://www.opengl-tutorial.org/intermediate-tutorials/tutorial-17-quaternions/
template <size_t S, typename T> template <size_t S, typename T>
quaternion<S,T> quaternion<S,T>
quaternion<S,T>::look (vector<3,T> fwd, vector<3,T> up) quaternion<S,T>::look (vector<3,T> fwd, vector<3,T> up)
@ -201,22 +203,23 @@ quaternion<S,T>::look (vector<3,T> fwd, vector<3,T> up)
CHECK (is_normalised (fwd)); CHECK (is_normalised (fwd));
CHECK (is_normalised (up)); CHECK (is_normalised (up));
constexpr util::vector3<T> RH_FWD { 0, 0, -1 }; constexpr util::vector3<T> FWD { 0, 0, -1 };
constexpr util::vector3<T> RH_UP { 0, 1, 0 }; constexpr util::vector3<T> UP { 0, 1, 0 };
// rotate the right-handed fwd to face the given fwd // find the rotation from the world fwd to the object fwd
auto q1 = from_to (RH_FWD, fwd); auto q1 = from_to (FWD, fwd);
// can't retain the up direction if fwd is the same as up // orthogonalise the up vector
if (norm2 (cross (fwd, up)) < 1e-6) auto right = cross (fwd, up);
return q1; auto orthup = normalised (cross (right, fwd));
// find the right-handed up rotated to the given fwd // recompute the up vector in object space
auto new_up = rotate (RH_UP, q1); auto newup = rotate (UP, q1);
// rotate first to the new forward, then align the right handed up with // find rotation from object up to world up
// the given up. auto q2 = from_to (newup, orthup);
return from_to (new_up, up) * q1;
return q2 * q1;
} }