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Inspect components

The Monitor Component

A SOFA component named Monitor (sofa::component::misc::Monitor) can help you to visualize, to monitor or to export some properties.

Quick overview of Monitor possibilities

With this component, you can see the positions, trajectories, velocities, forces of chosen particles directly in the GUI or save it into files (readable with Gnuplot for example). You can get an idea of what this component can make launching the examples/Component/SceneUtility/Monitor.scn scene.

Using the Monitor Component

To monitor properties you have to add a Monitor Component in your scene. Here is a selection of a piece of code of one of the Monitor of the example scene:

<Monitor template="Vec3d" name="velocities_8-16-24" listening="1" indices="8 16 24" showPositions="0" PositionsColor="1 1 0 1" showVelocities="1" VelocitiesColor="1 1 0 1" ForcesColor="1 1 0 1" showMinThreshold="0.01" TrajectoriesPrecision="0.1" TrajectoriesColor="1 1 0 1" sizeFactor="1" />

You can of course also add the component to your scene with the Modeler, look for Monitor in the search form. Required : for the Monitor to work you have to specify listening="1" or to set listening to true in the GUI. You have to select the properties you want to monitor or display.

  • If you want to visualize positions, you have to select showPositions (either clicking the corresponding field in the Visualization tab in the component GUI or adding showPositions="1" in your scene description file).
  • Then you can choose the color to be applied to your position visualization with PositionsColor and if needed the size of the visualization with sizeFactor.
  • You have to select the dofs that you want to monitor using the classic indices field : indices="8 16 24".
  • You can choose to export the positions of your dofs with ExportPositions. The positions will be exported to a file named following this rule : your_monitor_component_name+_x.txt in your Sofa directory.
             Field                     XML                      example                         Default Comments
             `indices`                 `""`                     `indices="0 2 4"`               *select the dofs to be monitored*

Positions showPositions false showPositions="true" to monitor positions Positions PositionsColor (1.0, 1.0, 0.0, 1.0) PositionsColor="1 1 0 1" to visualize the positions as some yellow points Positions ExportPositions false ExportPositions="true" positions will be exported to ${component_name}_x.txt Velocities showVelocities false showVelocities="true" to monitor velocities Velocities VelocitiesColor (1.0, 1.0, 0.0, 1.0) VelocitiesColor="1 0 1 1" to visualize the velocities as some purple arrows Velocities ExportVelocities false ExportVelocities="true" velocities will be exported to **${component_name}_v.txt Forces showForces false showForces="true" to monitor forces Forces ForcesColor (1.0, 1.0, 0.0, 1.0) ForcesColor="1 0 0 1" to visualize the forces as some red arrows Forces ExportForces false ExportForces="true" forces will be exported to ${component_name}_f.txt Trajectories showTrajectories false showTrajectories="true" to visualize the trajectories Trajectories TrajectoriesColor (1.0, 1.0, 0.0, 1.0) TrajectoriesColor="1 0 1 1" to get nice purple trajectories represented as lines Trajectories TrajectoriesPrecision 1.0 TrajectoriesPrecision="0.1" to specify the time step between two positions saving to reconstruct the trajectory sizeFactor 1.0 sizeFactor="true" to change the size of the drawing (points, arrows or lines) showMinThreshold 0.01 showMinThreshold="0.01" under this value, vectors are not represented

Visualize the result

To read the resulting file, you can use Gnuplot. In Gnuplot, you can for instance run the following command to render curves of your export file: 

splot "monitor-displacement-faceNode_x.txt"

See more Gnuplot examples here.

The ExtraMonitor Component, a Monitor extension

The ExtraMonitor component gives you the ability to use everything that it is in Monitor with some Extra stuff. It has been written to allow to compute, for example, the resultant of the forces of all the dofs of a MechanicalObject, or the minimum displacement of a region...

Using ExtraMonitor

Include the ExtraMonitor in your scene. Here is an example of use :

<ExtraMonitor template="Vec3d" name="velocities_8-16-24" listening="1" indices="8 16 24" showPositions="0" PositionsColor="1 1 0 1" showVelocities="1" VelocitiesColor="1 1 0 1" ForcesColor="1 1 0 1" showMinThreshold="0.01" TrajectoriesPrecision="0.1" TrajectoriesColor="1 1 0 1" sizeFactor="1" ExportWcin="false" ExportWext="false" resultantF="true" />
  • With this xml code, we say we want to use an ExtraMonitor named 'Socle' with every indices read in the indices field of the Engine named 'engineToto'. (We suppose 'engineToto' has been defined before).
  • Then we say we would like to export forces in a file but we set resultantF to true to precise we want to export the resultant of the dofs forces and not the forces of each of the dofs given in the indices set.
  • We also export positions but again we don't want every positions to be written down in the selected flag. We choose to export the minimum displacement and the maximum displacement of our set of particles. minCoord contains the number of the coordinate (0 stands for x, 1 stands for y, 2 stands for z in a 3D) for which we want to get the displacement. The same for maxCoord. Defaults values are -1 which means we don't want to export the corresponding displacement.

Additions

ExtraMonitor does not add visualization possibilities but it adds export possibilities.

          Field          XML                      example               Default Comments
          `indices`      `""`                     `indices="0 2 4"`     *select the dofs to be monitored*

Energy ExportWcin false ExportWcin="true" export kinetic energy computed by Mass in the context of the Monitor (need not indices to be set), exported to ${component_name}_wcin.txt Energy ExportWext (1.0, 1.0, 0.0, 1.0) ExportWext="true" export potential energy computed by the Mass in the context of the Monitor (need not indices to be set), exported to **${component_name}_wext.txt Forces resultantF false resultantF="true" to export force resultant of the monitored dofs in a gnuplot file, ExportForces must be set to true Positions minCoord -1 minCoord="2" gives the coordinate on which we want to monitor the minimum displacement of a set of dofs, ExportPositions must be set to **true Positions maxCoord -1 maxCoord="1" gives the coordinate on which we want to monitor the minimum displacement of a set of dofs, ExportPositions must be set to true Positions dispCoord -1 dispCoord="0" gives the coordinate on which we want to export the displacement of the given dofs, ExportPositions must be set to **true