Merge branch 'fix-quaternion-convention' into 'development'

Fix quaternion convention

See merge request damask/DAMASK!123

python/damask/orientation.py

@@ -26,7 +26,8 @@ class Rotation:
     Convention 4: Euler angle triplets are implemented using the Bunge convention,
                   with the angular ranges as [0, 2π],[0, π],[0, 2π].
     Convention 5: The rotation angle ω is limited to the interval [0, π].
-    Convention 6: P = -1 (as default).
+    Convention 6: the real part of a quaternion is positive, Re(q) > 0
+    Convention 7: P = -1 (as default).
     
     Usage
     -----

src/quaternions.f90

@@ -48,10 +48,7 @@ module quaternions
     procedure, private :: pow_scal__
     generic,   public  :: operator(**) => pow_quat__, pow_scal__
 
-    procedure, public  :: abs__
+    procedure, public  :: abs   => abs__
-    procedure, public  :: dot_product__
-    procedure, public  :: exp__
-    procedure, public  :: log__
     procedure, public  :: conjg => conjg__
     procedure, public  :: real  => real__
     procedure, public  :: aimag => aimag__
@@ -317,17 +314,17 @@ end function pow_scal__
 !---------------------------------------------------------------------------------------------------
 !> take exponential
 !---------------------------------------------------------------------------------------------------
-type(quaternion) elemental pure function exp__(self)
+type(quaternion) elemental pure function exp__(a)
 
-  class(quaternion), intent(in) :: self
+  class(quaternion), intent(in) :: a
   real(pReal)                   :: absImag
 
-  absImag = norm2(aimag(self))
+  absImag = norm2(aimag(a))
 
-  exp__ = merge(exp(self%w) * [                 cos(absImag), &
+  exp__ = merge(exp(a%w) * [               cos(absImag), &
-                               self%x/absImag * sin(absImag), &
+                             a%x/absImag * sin(absImag), &
-                               self%y/absImag * sin(absImag), &
+                             a%y/absImag * sin(absImag), &
-                               self%z/absImag * sin(absImag)], &
+                             a%z/absImag * sin(absImag)], &
                 IEEE_value(1.0_pReal,IEEE_SIGNALING_NAN), &
                 dNeq0(absImag))
 
@@ -337,17 +334,17 @@ end function exp__
 !---------------------------------------------------------------------------------------------------
 !> take logarithm
 !---------------------------------------------------------------------------------------------------
-type(quaternion) elemental pure function log__(self)
+type(quaternion) elemental pure function log__(a)
 
-  class(quaternion), intent(in) :: self
+  class(quaternion), intent(in) :: a
   real(pReal)                   :: absImag
 
-  absImag = norm2(aimag(self))
+  absImag = norm2(aimag(a))
 
-  log__ = merge([log(abs(self)), &
+  log__ = merge([log(abs(a)), &
-                 self%x/absImag * acos(self%w/abs(self)), &
+                 a%x/absImag * acos(a%w/abs(a)), &
-                 self%y/absImag * acos(self%w/abs(self)), &
+                 a%y/absImag * acos(a%w/abs(a)), &
-                 self%z/absImag * acos(self%w/abs(self))], &
+                 a%z/absImag * acos(a%w/abs(a))], &
                 IEEE_value(1.0_pReal,IEEE_SIGNALING_NAN), &
                 dNeq0(absImag))
 
@@ -357,11 +354,11 @@ end function log__
 !---------------------------------------------------------------------------------------------------
 !> return norm
 !---------------------------------------------------------------------------------------------------
-real(pReal) elemental pure function abs__(a)
+real(pReal) elemental pure function abs__(self)
 
-  class(quaternion), intent(in) :: a
+  class(quaternion), intent(in) :: self
 
-  abs__ = norm2([a%w,a%x,a%y,a%z])
+  abs__ = norm2([self%w,self%x,self%y,self%z])
 
 end function abs__
 
@@ -381,11 +378,11 @@ end function dot_product__
 !---------------------------------------------------------------------------------------------------
 !> take conjugate complex
 !---------------------------------------------------------------------------------------------------
-type(quaternion) elemental pure function conjg__(a)
+type(quaternion) elemental pure function conjg__(self)
 
-  class(quaternion), intent(in) :: a
+  class(quaternion), intent(in) :: self
 
-  conjg__ = [a%w, -a%x, -a%y, -a%z]
+  conjg__ = [self%w,-self%x,-self%y,-self%z]
 
 end function conjg__
 

src/rotations.f90

@@ -42,7 +42,8 @@
 !    Convention 4: Euler angle triplets are implemented using the Bunge convention,
 !                  with the angular ranges as [0, 2π],[0, π],[0, 2π]
 !    Convention 5: the rotation angle ω is limited to the interval [0, π]
-!    Convention 6: P = -1
+!    Convention 6: the real part of a quaternion is positive, Re(q) > 0
+!    Convention 7: P = -1
 !---------------------------------------------------------------------------------------------------
 
 module rotations
@@ -77,6 +78,7 @@ module rotations
       procedure, public  :: rotTensor4
       procedure, public  :: rotTensor4sym
       procedure, public  :: misorientation
+      procedure, public  :: standardize
   end type rotation
   
   public :: &
@@ -92,7 +94,7 @@ contains
 subroutine rotations_init
 
   call quaternions_init
-  write(6,'(/,a)')   ' <<<+-  rotations init  -+>>>'
+  write(6,'(/,a)') ' <<<+-  rotations init  -+>>>'; flush(6)
   call unitTest
 
 end subroutine rotations_init
@@ -237,7 +239,6 @@ end subroutine fromMatrix
 
 !---------------------------------------------------------------------------------------------------
 !> @brief: Rotate a rotation
-!> ToDo: completly untested
 !---------------------------------------------------------------------------------------------------
 pure elemental function rotRot__(self,R) result(rRot)
     
@@ -245,10 +246,23 @@ pure elemental function rotRot__(self,R) result(rRot)
   class(rotation), intent(in) :: self,R
   
   rRot = rotation(self%q*R%q)
+  call rRot%standardize()
 
 end function rotRot__
 
 
+!---------------------------------------------------------------------------------------------------
+!> @brief quaternion representation with positive q 
+!---------------------------------------------------------------------------------------------------
+pure elemental subroutine standardize(self)
+
+  class(rotation), intent(inout) :: self
+  
+  if (real(self%q) < 0.0_pReal) self%q = self%q%homomorphed()
+
+end subroutine standardize
+
+
 !---------------------------------------------------------------------------------------------------
 !> @author Marc De Graef, Carnegie Mellon University
 !> @brief rotate a vector passively (default) or actively
@@ -375,7 +389,7 @@ pure elemental function misorientation(self,other)
   type(rotation)              :: misorientation
   class(rotation), intent(in) :: self, other
   
-  misorientation%q = conjg(self%q) * other%q                                                        !ToDo: this is the convention used in math
+  misorientation%q = other%q * conjg(self%q)
 
 end function misorientation