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ConstantForceField

This component belongs to the category of ForceField. The ConstantForceField is a simple force field applying the same constant force on each node. This force field is not integrated over the domain of our object, but simply distributed over the number of nodes.

Data

  • indices: list of node indices where the forces are applied and distributed
  • force: single value corresponding to the constant force applied on each node
  • totalForce: single value corresponding to total force for all points, i.e. the sum of the forces distributed uniformly over the nodes
  • forces: vector containing the force amplitude applied at each node

Usage

As a Forcefield, the ConstantForceField requires a MechanicalObject and the associated solvers (integration scheme and linear solver), as well as a PointSetTopologyContainer.

Example

This component is used as follows in XML format:

<ConstantForceField indices="0 1 2" forces="-1 -1 0   1 -1 0   1 1 0" />

or using SofaPython3:

node.addObject('ConstantForceField', indices=[0 1 2], forces=[[-1 -1 0] [1 -1 0] [1 1 0]])

With a description of each data

An example scene involving a ConstantForceField is available in examples/Component/MechanicalLoad/ConstantForceField.scn

Target: Sofa.Component.MechanicalLoad

namespace: sofa::component::mechanicalload

parents:

  • ForceField

Data:

Name Description Default value
name object name unnamed
printLog if true, emits extra messages at runtime. 0
tags list of the subsets the objet belongs to
bbox this object bounding box
componentState The state of the component among (Dirty, Valid, Undefined, Loading, Invalid). Undefined
listening if true, handle the events, otherwise ignore the events 0
isCompliance Consider the component as a compliance, else as a stiffness 0
rayleighStiffness Rayleigh damping - stiffness matrix coefficient 0
indices indices where the forces are applied
indexFromEnd Concerned DOFs indices are numbered from the end of the MState DOFs vector. (default=false) 0
Force info
forces applied forces at each point
totalForce total force for all points, will be distributed uniformly over points
Visualization
showArrowSize Size of the drawn arrows (0->no arrows, sign->direction of drawing. (default=0) 0
showColor Color for object display (default: [0.2,0.9,0.3,1.0]) 0.2 0.9 0.3 1

Links:

Name Description
context Graph Node containing this object (or BaseContext::getDefault() if no graph is used)
slaves Sub-objects used internally by this object
master nullptr for regular objects, or master object for which this object is one sub-objects
mechanicalStates List of mechanical states to which this component is associated
mstate MechanicalState used by this component
topology link to the topology container

Examples

Component/MechanicalLoad/ConstantForceField.scn

<Node name="root" dt="0.05" gravity="0 0 0">
    <RequiredPlugin name="Sofa.Component.IO.Mesh"/> <!-- Needed to use components [MeshOBJLoader] -->
    <RequiredPlugin name="Sofa.Component.LinearSolver.Iterative"/> <!-- Needed to use components [CGLinearSolver] -->
    <RequiredPlugin name="Sofa.Component.Mapping.Linear"/> <!-- Needed to use components [IdentityMapping] -->
    <RequiredPlugin name="Sofa.Component.Mapping.NonLinear"/> <!-- Needed to use components [RigidMapping] -->
    <RequiredPlugin name="Sofa.Component.Mass"/> <!-- Needed to use components [UniformMass] -->
    <RequiredPlugin name="Sofa.Component.MechanicalLoad"/> <!-- Needed to use components [ConstantForceField] -->
    <RequiredPlugin name="Sofa.Component.ODESolver.Backward"/> <!-- Needed to use components [EulerImplicitSolver] -->
    <RequiredPlugin name="Sofa.Component.SolidMechanics.FEM.Elastic"/> <!-- Needed to use components [TriangleFEMForceField] -->
    <RequiredPlugin name="Sofa.Component.StateContainer"/> <!-- Needed to use components [MechanicalObject] -->
    <RequiredPlugin name="Sofa.Component.Topology.Container.Constant"/> <!-- Needed to use components [MeshTopology] -->
    <RequiredPlugin name="Sofa.Component.Visual"/> <!-- Needed to use components [InteractiveCamera VisualStyle] -->
    <RequiredPlugin name="Sofa.GL.Component.Rendering3D"/> <!-- Needed to use components [OglModel] -->
    <!-- Constant force for a deformable -->
    <VisualStyle displayFlags="showBehaviorModels showForceFields" />
    <DefaultAnimationLoop computeBoundingBox="false"/>
    <InteractiveCamera position="1.27 0.48 4.5" orientation="0 0 0 1"  distance="3.86" fieldOfView="45"/>

    <Node name="BasicDeformableObject" >
        <EulerImplicitSolver name="cg_odesolver" printLog="false"  rayleighMass="0.1" />
        <CGLinearSolver iterations="25" name="linear solver" tolerance="1.0e-9" threshold="1.0e-9" />
        <MechanicalObject position="0 0 0  1 0 0  1 1 0  0 1 0" velocity="0 0 0  0 0 0  0 0 0  0 0 0" />
        <UniformMass vertexMass="0.1" />
        <MeshTopology triangles="0 1 2  0 2 3" />
        <!--        <FixedProjectiveConstraint indices="2 3"/>-->
        <TriangleFEMForceField name="FEM0" youngModulus="100" poissonRatio="0.3" method="large" />
        <ConstantForceField indices="0 1 2 3" forces="-1 -1 0  1 -1 0  1 1 0  -1 1 0" showArrowSize="0.5" printLog="1"/>
        <Node name="Visu">
            <OglModel name="Visual" color="red" />
            <IdentityMapping input="@.." output="@Visual" />
        </Node>
    </Node>
    <Node name="TorusRigid">
        <EulerImplicitSolver rayleighStiffness="0.01" />
        <CGLinearSolver iterations="25" threshold="0.00000001" tolerance="1e-5"/>
        <MechanicalObject template="Rigid3" dx="2" dy="0" dz="0" rx="0" ry="0" rz="0" scale="1.0" />
        <UniformMass />
        <!-- forces for a rigid is composed of two parts translation of the rigid dof [x y z] and a quaternion for the rotation [x y z w] -->
        <ConstantForceField indices="0" forces="0 0.10 0     0 1 0" />
        <Node name="Visu">
            <MeshOBJLoader name="meshLoader_0" filename="mesh/torus.obj" scale="0.3" handleSeams="1" />
            <OglModel name="Visual" src="@meshLoader_0" color="gray" />
            <RigidMapping input="@.." output="@Visual" />
        </Node>
    </Node>
</Node>

def createScene(rootNode):

    root = rootNode.addChild('root', dt="0.05", gravity="0 0 0")
    root.addObject('RequiredPlugin', name="Sofa.Component.IO.Mesh")
    root.addObject('RequiredPlugin', name="Sofa.Component.LinearSolver.Iterative")
    root.addObject('RequiredPlugin', name="Sofa.Component.Mapping.Linear")
    root.addObject('RequiredPlugin', name="Sofa.Component.Mapping.NonLinear")
    root.addObject('RequiredPlugin', name="Sofa.Component.Mass")
    root.addObject('RequiredPlugin', name="Sofa.Component.MechanicalLoad")
    root.addObject('RequiredPlugin', name="Sofa.Component.ODESolver.Backward")
    root.addObject('RequiredPlugin', name="Sofa.Component.SolidMechanics.FEM.Elastic")
    root.addObject('RequiredPlugin', name="Sofa.Component.StateContainer")
    root.addObject('RequiredPlugin', name="Sofa.Component.Topology.Container.Constant")
    root.addObject('RequiredPlugin', name="Sofa.Component.Visual")
    root.addObject('RequiredPlugin', name="Sofa.GL.Component.Rendering3D")
    root.addObject('VisualStyle', displayFlags="showBehaviorModels showForceFields")
    root.addObject('DefaultAnimationLoop', computeBoundingBox="false")
    root.addObject('InteractiveCamera', position="1.27 0.48 4.5", orientation="0 0 0 1", distance="3.86", fieldOfView="45")

    BasicDeformableObject = root.addChild('BasicDeformableObject')
    BasicDeformableObject.addObject('EulerImplicitSolver', name="cg_odesolver", printLog="false", rayleighMass="0.1")
    BasicDeformableObject.addObject('CGLinearSolver', iterations="25", name="linear solver", tolerance="1.0e-9", threshold="1.0e-9")
    BasicDeformableObject.addObject('MechanicalObject', position="0 0 0  1 0 0  1 1 0  0 1 0", velocity="0 0 0  0 0 0  0 0 0  0 0 0")
    BasicDeformableObject.addObject('UniformMass', vertexMass="0.1")
    BasicDeformableObject.addObject('MeshTopology', triangles="0 1 2  0 2 3")
    BasicDeformableObject.addObject('TriangleFEMForceField', name="FEM0", youngModulus="100", poissonRatio="0.3", method="large")
    BasicDeformableObject.addObject('ConstantForceField', indices="0 1 2 3", forces="-1 -1 0  1 -1 0  1 1 0  -1 1 0", showArrowSize="0.5", printLog="1")

    Visu = BasicDeformableObject.addChild('Visu')
    Visu.addObject('OglModel', name="Visual", color="red")
    Visu.addObject('IdentityMapping', input="@..", output="@Visual")

    TorusRigid = root.addChild('TorusRigid')
    TorusRigid.addObject('EulerImplicitSolver', rayleighStiffness="0.01")
    TorusRigid.addObject('CGLinearSolver', iterations="25", threshold="0.00000001", tolerance="1e-5")
    TorusRigid.addObject('MechanicalObject', template="Rigid3", dx="2", dy="0", dz="0", rx="0", ry="0", rz="0", scale="1.0")
    TorusRigid.addObject('UniformMass')
    TorusRigid.addObject('ConstantForceField', indices="0", forces="0 0.10 0     0 1 0")

    Visu = TorusRigid.addChild('Visu')
    Visu.addObject('MeshOBJLoader', name="meshLoader_0", filename="mesh/torus.obj", scale="0.3", handleSeams="1")
    Visu.addObject('OglModel', name="Visual", src="@meshLoader_0", color="gray")
    Visu.addObject('RigidMapping', input="@..", output="@Visual")