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[Jan Stránský <question688763@xxxxxxxxxxxxxxxxxxxxx>]

Question #688763 on Yade changed:
https://answers.launchpad.net/yade/+question/688763

Jan Stránský posted a new comment:
Hi,

sorry for late answer..

> Because in my simulation I still have some particles, the particles
also have the orientations, I just want the shaft rotates under certain
degrees. so I use, "for b in O.bodies" and "if
isinstance(b.shape,Facet):" to isolate the degrees that the shaft has
been rotated.

in principle it should work as it is now, but the for loop is no
necessary and overall it more error prone IMO

cylinderRot and coneRot controls all of its bodies, so it should be sufficient to only use e.g. its first body:
###
def ossillation_rotation():
 i = cylinderRot.ids[0]
 b = O.bodies[i]
 rotationAngle = b.state.rot().norm() # needs to update, but the point is using just one body
 if rotationAngle > 0 ...
  ...
 else:
  ...
###

> so if I want the shaft rotates 200 degrees, I can't
use,O.bodies.state.rot().nrom(), this command??

yes, you cannot use it. As I have written, the solution is to store actual rotation and add incrementally the rotation increment to the stored value. MWE with one facet:
###
b = facet(((0,0,0),(1,0,0),(0,1,0)))
O.bodies.append(b)
b.state.angVel = (0,0,.1)

rot = 0
ori = b.state.refOri

def updateRot(b,rot,ori): # works for rotation aroud z axis
   relRot = ori.conjugate()*b.state.ori # same as State.rot(), https://gitlab.com/yade-dev/trunk/-/blob/master/core/State.hpp#L40
   axis,angle = relRot.toAxisAngle() # get axis and angle from quaternion
   if (axis[2]) < 0: # "negative" rotation ...
      angle *= -1 # ... negate the positive angle
   rot += angle # updates rotation angle
   ori = b.state.ori # "store" new orientation value
   return rot,ori

for i in range(20):
   O.step()
   rot,ori = updateRot(b,rot,ori)
   print i,rot

b.state.angVel = (0,0,-.3)

for i in range(40):
   O.step()
   rot,ori = updateRot(b,rot,ori)
   print i,rot
###

cheers
Jan

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