DiagonalMass
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Context: Sofa.Component.Mass

Define a specific mass for each particle

Data:
 - name : object name
 - printLog : if true, emits extra messages at runtime.
 - 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).
 - listening : if true, handle the events, otherwise ignore the events
 - isCompliance : Consider the component as a compliance, else as a stiffness
 - rayleighStiffness : Rayleigh damping - stiffness matrix coefficient
 - separateGravity : add separately gravity to velocity computation
 - rayleighMass : Rayleigh damping - mass matrix coefficient
 - vertexMass : Specify a vector giving the mass of each vertex. 
If unspecified or wrongly set, the massDensity or totalMass information is used.
 - massDensity : Specify one single real and positive value for the mass density. 
If unspecified or wrongly set, the totalMass information is used.
 - totalMass : Specify the total mass resulting from all particles. 
If unspecified or wrongly set, the default value is used: totalMass = 1.0
 - computeMassOnRest : If true, the mass of every element is computed based on the rest position rather than the position
 - showGravityCenter : Display the center of gravity of the system
 - showAxisSizeFactor : Factor length of the axis displayed (only used for rigids)
 - filename : Xsp3.0 file to specify the mass parameters

Links:
 - 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
 - geometryState : link to the MechanicalObject associated with the geometry