/
Quaternion.jl
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Quaternion.jl
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immutable Quaternion{T<:Real} <: Number
s::T
v1::T
v2::T
v3::T
norm::Bool
end
Quaternion(s::Real, v1::Real, v2::Real, v3::Real, n::Bool = false) =
Quaternion( promote(s, v1, v2, v3)..., n)
Quaternion(x::Real) = Quaternion(x, zero(x), zero(x), zero(x), abs(x) == one(x))
Quaternion(z::Complex) = Quaternion(z.re, z.im, zero(z.re), zero(z.re), abs(z) == one(z.re))
Quaternion(s::Real, a::Vector) = Quaternion(s, a[1], a[2], a[3])
Quaternion(a::Vector) = Quaternion(0, a[1], a[2], a[3])
convert{T}(::Type{Quaternion{T}}, x::Real) =
Quaternion(convert(T,x), convert(T,0), convert(T,0), convert(T,0))
convert{T}(::Type{Quaternion{T}}, z::Complex) =
Quaternion(convert(T,real(z)), convert(T,imag(z)), convert(T,0), convert(T,0))
convert{T<:Real}(::Type{Quaternion{T}}, q::Quaternion{T}) = q
convert{T}(::Type{Quaternion{T}}, q::Quaternion) =
Quaternion(convert(T,q.s), convert(T,q.v1), convert(T,q.v2), convert(T,q.v3), q.norm)
promote_rule{T<:Real}(::Type{Quaternion{T}}, ::Type{T}) = Quaternion{T}
promote_rule{T<:Real}(::Type{Quaternion}, ::Type{T}) = Quaternion
promote_rule{T<:Real,S<:Real}(::Type{Quaternion{T}}, ::Type{S}) = Quaternion{promote_type(T,S)}
promote_rule{T<:Real,S<:Real}(::Type{Complex{T}}, ::Type{Quaternion{S}}) = Quaternion{promote_type(T,S)}
promote_rule{T<:Real,S<:Real}(::Type{Quaternion{T}}, ::Type{Quaternion{S}}) = Quaternion{promote_type(T,S)}
quat(p, v1, v2, v3, n = false) = Quaternion(p, v1, v2, v3, n)
quat(x) = Quaternion(x)
quat(s, a) = Quaternion(s, a)
function show(io::IO, q::Quaternion)
pm(x) = x < 0 ? " - $(-x)" : " + $x"
print(io, q.s, pm(q.v1), "im", pm(q.v2), "jm", pm(q.v3), "km")
end
real{T}(::Type{Quaternion{T}}) = T
real(q::Quaternion) = q.s
imag(q::Quaternion) = [q.v1, q.v2, q.v3]
(/)(q::Quaternion, x::Real) = Quaternion(q.s/x, q.v1/x, q.v2/x, q.v3/x)
conj(q::Quaternion) = Quaternion(q.s, -q.v1, -q.v2, -q.v3, q.norm)
abs(q::Quaternion) = sqrt(q.s*q.s + q.v1*q.v1 + q.v2*q.v2 + q.v3*q.v3)
abs_imag(q::Quaternion) = sqrt(q.v1*q.v1 + q.v2*q.v2 + q.v3*q.v3)
abs2(q::Quaternion) = q.s*q.s + q.v1*q.v1 + q.v2*q.v2 + q.v3*q.v3
inv(q::Quaternion) = q.norm ? conj(q) : conj(q)/abs2(q)
isfinite(q::Quaternion) = q.norm ? true : (isfinite(q.s) && isfinite(q.v1) && isfinite(q.v2) && isfinite(q.v3))
function normalize(q::Quaternion)
if (q.norm)
return q
end
q = q / abs(q)
Quaternion(q.s, q.v1, q.v2, q.v3, true)
end
function normalizea(q::Quaternion)
if (q.norm)
return (q,one(q.s))
end
a = abs(q)
q = q / a
(Quaternion(q.s, q.v1, q.v2, q.v3, true), a)
end
function normalizeq(q::Quaternion)
a = abs(q)
if a > 0
q = q / a
Quaternion(q.s, q.v1, q.v2, q.v3, true)
else
Quaternion(0.0, 1.0, 0.0, 0.0, true)
end
end
(-)(q::Quaternion) = Quaternion(-q.s, -q.v1, -q.v2, -q.v3, q.norm)
(+)(q::Quaternion, w::Quaternion) =
Quaternion(q.s + w.s, q.v1 + w.v1, q.v2 + w.v2, q.v3 + w.v3)
(-)(q::Quaternion, w::Quaternion) =
Quaternion(q.s - w.s, q.v1 - w.v1, q.v2 - w.v2, q.v3 - w.v3)
(*)(q::Quaternion, w::Quaternion) = Quaternion(q.s*w.s - q.v1*w.v1 - q.v2*w.v2 - q.v3*w.v3,
q.s*w.v1 + q.v1*w.s + q.v2*w.v3 - q.v3*w.v2,
q.s*w.v2 - q.v1*w.v3 + q.v2*w.s + q.v3*w.v1,
q.s*w.v3 + q.v1*w.v2 - q.v2*w.v1 + q.v3*w.s,
q.norm && w.norm)
(/)(q::Quaternion, w::Quaternion) = q * inv(w)
angleaxis(q::Quaternion) = angle(q), axis(q)
angle(q::Quaternion) = 2*atan2(√(q.v1^2 + q.v2^2 + q.v3^2), q.s)
function axis(q::Quaternion)
q = normalize(q)
s = sin(angle(q) / 2)
abs(s) > 0 ?
[q.v1, q.v2, q.v3] / s :
[1.0, 0.0, 0.0]
end
argq(q::Quaternion) = normalizeq(Quaternion(0, q.v1, q.v2, q.v3))
function exp(q::Quaternion)
s = q.s
se = exp(s)
scale = se
th = abs_imag(q)
if th > 0
scale *= sin(th) / th
end
Quaternion(se*cos(th), scale*q.v1, scale*q.v2, scale*q.v3, abs(s) < eps(typeof(s)))
end
function log(q::Quaternion)
q, a = normalizea(q)
s = q.s
M = abs_imag(q)
th = atan2(M, s)
if M > 0
M = th / M
return Quaternion(log(a), q.v1*M, q.v2*M, q.v3*M)
else
return Quaternion(log(a), th , 0.0, 0.0)
end
end
function sin(q::Quaternion)
L = argq(q)
return (exp(L*q) - exp(-L*q))/(2*L)
end
function cos(q::Quaternion)
L = argq(q)
return (exp(L*q) + exp(-L*q)) / 2
end
(^)(q::Quaternion, w::Quaternion) = exp(w*log(q))
sqrt(q::Quaternion) = exp(0.5*log(q))
function linpol(p::Quaternion, q::Quaternion, t::Real)
p = normalize(p)
q = normalize(q)
qm = -q
if abs(p - q) > abs(p - qm)
q = qm
end
c = p.s * q.s + p.v1 * q.v1 + p.v2 * q.v2 + p.v3 * q.v3
if c > - 1.0
if c < 1.0
o = acos(c)
s = sin(o)
sp = sin((1 - t)*o)/s
sq = sin(t*o)/s
else
sp = 1 - t
sq = t
end
Quaternion(sp*p.s + sq*q.s,
sp*p.v1 + sq*q.v1,
sp*p.v2 + sq*q.v2,
sp*p.v3 + sq*q.v3, true)
else
s = p.v3
v1 = -p.v2
v2 = p.v1
v3 = -p.s
sp = sin((0.5 - t)*pi)
sq = sin(t*pi)
Quaternion(s,
sp * p.v1 + sq * v1,
sp * p.v2 + sq * v2,
sp * p.v3 + sq * v3, true)
end
end
quatrand() = quat(randn(), randn(), randn(), randn())
nquatrand() = normalize(quatrand())
## Rotations
function qrotation{T<:Real}(axis::Vector{T}, theta)
if length(axis) != 3
error("Must be a 3-vector")
end
u = normalize(axis)
thetaT = convert(eltype(u), theta)
s = sin(thetaT/2)
Quaternion(cos(thetaT/2), s*u[1], s*u[2], s*u[3], true)
end
# Variant of the above where norm(rotvec) encodes theta
function qrotation{T<:Real}(rotvec::Vector{T})
if length(rotvec) != 3
error("Must be a 3-vector")
end
theta = norm(rotvec)
if theta > 0
s = sin(theta/2)/theta # divide by theta to make rotvec a unit vector
return Quaternion(cos(theta/2), s*rotvec[1], s*rotvec[2], s*rotvec[3], true)
end
Quaternion(one(T), zero(T), zero(T), zero(T), true)
end
rotationmatrix(q::Quaternion) = rotationmatrix_normalized(normalize(q))
function rotationmatrix_normalized(q::Quaternion)
sx, sy, sz = 2q.s*q.v1, 2q.s*q.v2, 2q.s*q.v3
xx, xy, xz = 2q.v1^2, 2q.v1*q.v2, 2q.v1*q.v3
yy, yz, zz = 2q.v2^2, 2q.v2*q.v3, 2q.v3^2
[1-(yy+zz) xy-sz xz+sy;
xy+sz 1-(xx+zz) yz-sx;
xz-sy yz+sx 1-(xx+yy)]
end
function normalize{T}(v::Vector{T})
nv = norm(v)
if nv > 0
return v/nv
end
zeros(promote_type(T,typeof(nv)), length(v))
end
function slerp{T}(qa::Quaternion{T}, qb::Quaternion{T}, t::T)
# http://www.euclideanspace.com/maths/algebra/realNormedAlgebra/quaternions/slerp/
coshalftheta = qa.s * qb.s + qa.v1 * qb.v1 + qa.v2 * qb.v2 + qa.v3 * qb.v3;
if coshalftheta < 0
qm = -qb
coshalftheta = -coshalftheta
else
qm = qb
end
abs(coshalftheta) >= 1.0 && return qa
halftheta = acos(coshalftheta)
sinhalftheta = sqrt(one(T) - coshalftheta * coshalftheta)
if abs(sinhalftheta) < 0.001
return Quaternion(
T(0.5) * (qa.s + qb.s),
T(0.5) * (qa.v1 + qb.v1),
T(0.5) * (qa.v2 + qb.v2),
T(0.5) * (qa.v3 + qb.v3),
)
end
ratio_a = sin((one(T) - t) * halftheta) / sinhalftheta
ratio_b = sin(t * halftheta) / sinhalftheta
Quaternion(
qa.s * ratio_a + qm.s * ratio_b,
qa.v1 * ratio_a + qm.v1 * ratio_b,
qa.v2 * ratio_a + qm.v2 * ratio_b,
qa.v3 * ratio_a + qm.v3 * ratio_b,
)
end