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[Jan Stránský <question691171@xxxxxxxxxxxxxxxxxxxxx>]

Question #691171 on Yade changed:
https://answers.launchpad.net/yade/+question/691171

    Status: Open => Answered

Jan Stránský proposed the following answer:
Concerning random orientation, you can try the approach from [3]
###
def randomOrientation():
   # from the source code of Quaternion::UnitRandom()
   # https://eigen.tuxfamily.org/dox-devel/Quaternion_8h_source.html
   from random import random as r
   u1 = r()
   u2 = r() * pi
   u3 = r() * pi
   a = sqrt(1 - u1)
   b = sqrt(u1)
   return Quaternion(a*sin(u2),a*cos(u2),b*sin(u3),b*cos(u3))
# test
O.bodies.append([box((0,0,0),(10,1,.1),orientation=randomOrientation()) for _ in range(50)])
O.step()
###

> i still wonder how same codes turn out to be "create some spheres,
meant to be actual spheres in simulation" and "create some spheres
("fibre-spheres"), meant just to reserve space for fibres (not added to
the simulation)"

this I did not get..
what is "same code"?

> ……and i need to calculate two mass of spheres and cylinders, how can i
distinguish them with codes.

spheres = [b for b in O.bodies if isisntance(b.shape,Sphere)]
massSpheres = sum(b.state.mass for b in spheres)

(facet)cylinders - depends if sum is needed etc..

You can also have the two lists directly from the code:
###
cyls = []
sphs = []
for i,(pos,radius) in enumerate(sp):
    if i < nCyls: # add cylinder
      cyl =  geom.facetCylinder(...)
      O.bodies.append(cyl)
      cyls.append(cyl)
    else: # add sphere
      sph = sphere(pos,radius)
      O.bodies.append(sph)
      sphs.append(sph)
# do whetever with sphs and cyls lists
###

If you need specific masses for spheres and cylinders, you can modify the procedure a bit:
1) create spheres, add them to simulation, compute their mass if needed
2) create "fibre-spheres"
3) replace "fibre-spheres" by fibres one by one (also add them to simulation one by one). If the desired fibre mass matches desired value, stop replacing and adding fibres.

cheers
Jan

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