DAMASK_EICMD/python/damask/quaternion.py

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# -*- coding: UTF-8 no BOM -*-
import numpy as np
P = -1 # convention (see DOI:10.1088/0965-0393/23/8/083501)
####################################################################################################
class Quaternion:
u"""
Quaternion with basic operations
q is the real part, p = (x, y, z) are the imaginary parts.
Definition of multiplication depends on variable P, P {-1,1}.
"""
def __init__(self,
q = 0.0,
p = np.zeros(3,dtype=float)):
"""Initializes to identity unless specified"""
self.q = float(q)
self.p = np.array(p,dtype=float)
def __copy__(self):
"""Copy"""
return self.__class__(q=self.q,
p=self.p.copy())
copy = __copy__
def __iter__(self):
"""Components"""
return iter(self.asList())
def __repr__(self):
"""Readable string"""
return 'Quaternion: (real={q:+.6f}, imag=<{p[0]:+.6f}, {p[1]:+.6f}, {p[2]:+.6f}>)'.format(q=self.q,p=self.p)
def __add__(self, other):
"""Addition"""
if isinstance(other, Quaternion):
return self.__class__(q=self.q + other.q,
p=self.p + other.p)
else:
return NotImplemented
def __iadd__(self, other):
"""In-place addition"""
if isinstance(other, Quaternion):
self.q += other.q
self.p += other.p
return self
else:
return NotImplemented
def __pos__(self):
"""Unary positive operator"""
return self
def __sub__(self, other):
"""Subtraction"""
if isinstance(other, Quaternion):
return self.__class__(q=self.q - other.q,
p=self.p - other.p)
else:
return NotImplemented
def __isub__(self, other):
"""In-place subtraction"""
if isinstance(other, Quaternion):
self.q -= other.q
self.p -= other.p
return self
else:
return NotImplemented
def __neg__(self):
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"""Unary negative operator"""
return self * -1.0
def __mul__(self, other):
"""Multiplication with quaternion or scalar"""
if isinstance(other, Quaternion):
return self.__class__(q=self.q*other.q - np.dot(self.p,other.p),
p=self.q*other.p + other.q*self.p + P * np.cross(self.p,other.p))
elif isinstance(other, (int, float)):
return self.__class__(q=self.q*other,
p=self.p*other)
else:
return NotImplemented
def __imul__(self, other):
"""In-place multiplication with quaternion or scalar"""
if isinstance(other, Quaternion):
self.q = self.q*other.q - np.dot(self.p,other.p)
self.p = self.q*other.p + other.q*self.p + P * np.cross(self.p,other.p)
return self
elif isinstance(other, (int, float)):
self.q *= other
self.p *= other
return self
else:
return NotImplemented
def __truediv__(self, other):
"""Divsion with quaternion or scalar"""
if isinstance(other, Quaternion):
s = other.conjugate()/abs(other)**2.
return self.__class__(q=self.q * s,
p=self.p * s)
elif isinstance(other, (int, float)):
return self.__class__(q=self.q / other,
p=self.p / other)
else:
return NotImplemented
def __itruediv__(self, other):
"""In-place divsion with quaternion or scalar"""
if isinstance(other, Quaternion):
s = other.conjugate()/abs(other)**2.
self *= s
return self
elif isinstance(other, (int, float)):
self.q /= other
self.p /= other
return self
else:
return NotImplemented
def __pow__(self, exponent):
"""Power"""
if isinstance(exponent, (int, float)):
omega = np.acos(self.q)
return self.__class__(q= np.cos(exponent*omega),
p=self.p * np.sin(exponent*omega)/np.sin(omega))
else:
return NotImplemented
def __ipow__(self, exponent):
"""In-place power"""
if isinstance(exponent, (int, float)):
omega = np.acos(self.q)
self.q = np.cos(exponent*omega)
self.p *= np.sin(exponent*omega)/np.sin(omega)
return self
else:
return NotImplemented
def __abs__(self):
"""Norm"""
return np.sqrt(self.q ** 2 + np.dot(self.p,self.p))
magnitude = __abs__
def __eq__(self,other):
"""Equal (sufficiently close) to each other"""
return np.isclose(( self-other).magnitude(),0.0) \
or np.isclose((-self-other).magnitude(),0.0)
def __ne__(self,other):
"""Not equal (sufficiently close) to each other"""
return not self.__eq__(other)
def asM(self):
"""Intermediate representation useful for quaternion averaging (see F. Landis Markley et al.)"""
return np.outer(self.asArray(),self.asArray())
def asArray(self):
"""As numpy array"""
return np.array((self.q,self.p[0],self.p[1],self.p[2]))
def asList(self):
"""As list"""
return [self.q]+list(self.p)
def normalize(self):
"""Normalizes in-place"""
d = self.magnitude()
if d > 0.0: self /= d
return self
def normalized(self):
"""Returns normalized copy"""
return self.copy().normalize()
def conjugate(self):
"""Conjugates in-place"""
self.p = -self.p
return self
def conjugated(self):
"""Returns conjugated copy"""
return self.copy().conjugate()
def homomorph(self):
"""Homomorphs in-place"""
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self *= -1.0
return self
def homomorphed(self):
"""Returns homomorphed copy"""
return self.copy().homomorph()