# yade-users team mailing list archive

## Applying constant force on a wall and snapshot engine

```Hello,

I followed the advices that Mr Vaclav gave me and the code is below, but
my box is still falling with spheres, there is again something wrong? It
seems that only gravity is affecting bodyes.
Another point is that if I activate the snapshot engine it results in
blank images, there's a reason or a wrong setting?

Thank you

# -*- encoding=utf-8 -*-

from math import *
from numpy import arange
import random

## Paametri fisici geometrie importate
Young = 15e6
Poisson = 0.2

#Parametri cilindro
rCyl=40   ##Raggio superiore tronco cono
rCyl2=40  ##Raggio inferiore tronco cono
hCyl=39   ##altezza base inferiore cono
hCyl2=10 ##altezza base superiore cono
nPoly=20  ##Poligoni di cui Ã¨ composto il contenitore
hBox=hCyl/5
phiStep=2*pi/nPoly

#tolleranza contatti
toll = 0.005

## Omega
o=Omega()

## Importa geometria testa
utils.import_stl_geometry('TC3T4.stl',young=Young,poisson=Poisson,
color=[0,1,0],wire=True)

for n in range(nPoly):
phi1,phi2=n*phiStep,(n+1)*phiStep
a,b,c,d=pt(phi1,rCyl,hCyl2),pt(phi2,rCyl,hCyl2),pt(phi1,rCyl2,hCyl),pt(phi2,rCyl2,hCyl)
o.bodies.append([
utils.facet([a,b,c]),
utils.facet([b,c,d])])

for b in o.bodies: b['isDynamic']=False

box =
utils.box([0,0,hCyl+hBox/2],[rCyl,rCyl,hBox/2],density=200,wire=True)
boxId=o.bodies.append(box)

#for b in o.bodies: b['isDynamic']=False

## Sfere
nbSpheres = (10,10,3)
for i in xrange(nbSpheres[0]):
for j in xrange(nbSpheres[1]):
for k in xrange(nbSpheres[2]):
z = 31 + (k*2 - nbSpheres[2])*sphereRadius*1.2
utils.randomizeColors(onlyDynamic=True)

## Timestep
o.dt=utils.PWaveTimeStep()

## Initializers
o.initializers=[
## Create and reset to zero container of all PhysicalActions
that will be used
StandAloneEngine('PhysicalActionContainerInitializer'),
## Create bounding boxes. They are needed to zoom the 3d view
properly before we start the simulation.
MetaEngine('BoundingVolumeMetaEngine',[EngineUnit('InteractingSphere2AABB'),EngineUnit('InteractingFacet2AABB'),EngineUnit('InteractingBox2AABB'),EngineUnit('MetaInteractingGeometry2AABB')])
]

## Engines
o.engines=[

## Resets forces and momenta the act on bodies
StandAloneEngine('PhysicalActionContainerReseter'),

## Associates bounding volume to each body.
MetaEngine('BoundingVolumeMetaEngine',[
EngineUnit('InteractingSphere2AABB'),
EngineUnit('InteractingFacet2AABB'),
EngineUnit('InteractingBox2AABB'),
EngineUnit('MetaInteractingGeometry2AABB')
]),
## Using bounding boxes find possible body collisions.
##StandAloneEngine('SpatialQuickSortCollider'),
StandAloneEngine('SAPCollider'),
## Create geometry information about each potential collision.
MetaEngine('InteractionGeometryMetaEngine',[
EngineUnit('InteractingSphere2InteractingSphere4SpheresContactGeometry'),
EngineUnit('InteractingFacet2InteractingSphere4SpheresContactGeometry',{'shrinkFactor':toll}),
EngineUnit('InteractingBox2InteractingSphere4SpheresContactGeometry')
]),
## Crea informazioni fisiche sui contatti.
MetaEngine('InteractionPhysicsMetaEngine',[EngineUnit('MacroMicroElasticRelationships')]),
## "Solver" of the contact
StandAloneEngine('ElasticContactLaw'),

## Applica forza alla base
DeusExMachina('ForceEngine',{'subscribedBodies':[boxId],
'force':[0,0,-100]}),
## Sostituisce i motori di applicazione forze ai corpi,
smorzamento ed integrazione temporale
DeusExMachina('NewtonsDampedLaw',{'damping':0.3}),

## Applica rotazione alla testa 1 giro/min = 0,1047 rad/s
'rotationAxis':[0,0,1],'rotateAroundZero':True,'angularVelocity':0.1047}),

#StandAloneEngine('SnapshotEngine',{'virtPeriod':1,'fileBase':'aaa','viewNo':0,'ignoreErrors':True})

]

## Salva la scena da simulare
o.save('/tmp/a.xml');
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