component.constraint.SurfacePressureConstraint

In this directory you will find multiple examples showing how to use the SurfacePressureConstraint component:

• Springy.pyscn : Soft actuated accordion
• PressureVsVolumeGrowthControl.pyscn : Stanford bunny

Below is a video of a soft Standford bunny actuated with pressure in its inner cavity. You can run this simulation by loading the file PressureVsVolumeGrowthControl.pyscn with the application runSofa.

Example

#  This create a new node in the scene. This node is appended to the accordion's node.
cavity = accordion.createChild('cavity')

# This create a MechanicalObject, a componant holding the degree of freedom of our
# mechanical modelling. In the case of a pneumatic actuation it is a set of positions describing the cavity wall.
cavity.createObject('MeshSTLLoader', name='loader', filename=path+'Springy_Cavity.stl')
cavity.createObject('MeshTopology', src='@loader', name='topo')
cavity.createObject('MechanicalObject', name='cavity')

# Create a SurfacePressureConstraint object with a name.
cavity.createObject('SurfacePressureConstraint', template='Vec3', name="pressure",
                    triangles='@topo.triangles',
                    valueType="1",
                    value="8")

# This create a BarycentricMapping. A BarycentricMapping is a key element as it will create a bi-directional link
# between the cavity wall (surfacic mesh) and the accordion (volumetric mesh) so that movements of the cavity's DoFs will be mapped
# to the accordion and vice-versa;
cavity.createObject('BarycentricMapping', name='mapping',  mapForces=False, mapMasses=False)

Data fields

Required	Description
triangles	List of triangles on which the surface pressure is applied. If no list is given, the component will fill the two lists with the context topology.
quads	List of quads on which the surface pressure is applied. If no list is given, the component will fill the two lists with the context topology.
value	List of choices for volume growth or pressure to impose.
valueIndex	Index of the value (in InputValue vector) that we want to impose. If unspecified the default value is {0}.
valueType	Either “volumeGrowth”, the contstraint will impose the volume growth provided in data value[valueIndex], or “pressure”, in this case the contstraint will impose the pressure provided in data value[valueIndex]. If unspecified, the default value is pressure.

Optional	Description
flipNormal	Allows to invert cavity faces orientation. If a positive pressure acts like a depressurization, try to set flipNormal to true.
maxPressure	Maximum pressure allowed for actuation. If no value is set by user, no maximum pressure constraint will be considered.
minPressure	Minimum pressure allowed for actuation. If no value is set by user, no minimum pressure constraint will be considered. A negative pressure will empty/drain the cavity.
maxVolumeGrowth	Maximum volume growth allowed for actuation. If no value is set by user, no maximum will be considered. NB: this value has a dependancy with the time step (volume/dt) in the dynamic case.
minVolumeGrowth	Minimum volume growth allowed for actuation. If no value is set by user, no minimum will be considered. NB: this value has a dependancy with the time step (volume/dt) in the dynamic case.
maxVolumeGrowthVariation	Maximum volume growth variation allowed for actuation. If no value is set by user, no maximum will be considered. NB: this value has a dependancy with the time step (volume/dt) in the dynamic case.
drawPressure	Visualization of the value of pressure. If unspecified, the default value is {false}.
drawScale	Scale for visualization. If unspecified the default value is {0.1}.

Properties	Description
volumeGrowth	Read only. Output volume growth.
pressure	Read only. Output pressure.
initialCavityVolume	Read only. Output volume of the cavity at init (only relevant in case of closed mesh).
cavityVolume	Read only. Output volume of the cavity (only relevant in case of closed mesh).