Return a zero moment if a path does not depend on a coordinate

opensim-org · Sep 25, 2023 · dde9b2d · dde9b2d
1 parent 885fd34
commit dde9b2d
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Showing 2 changed files with 12 additions and 3 deletions.
diff --git a/OpenSim/Simulation/Model/FunctionBasedPath.cpp b/OpenSim/Simulation/Model/FunctionBasedPath.cpp
@@ -125,9 +125,14 @@ double FunctionBasedPath::getLength(const SimTK::State& s) const
 double FunctionBasedPath::computeMomentArm(const SimTK::State& s, 
         const Coordinate& coord) const 
 {
-    computeMomentArms(s);
-    return getCacheVariableValue<SimTK::Vector>(s, MOMENT_ARMS_NAME)
-            .get(_coordinateIndices.at(coord.getAbsolutePathString()));
+    if (_coordinateIndices.find(coord.getAbsolutePathString()) != 
+            _coordinateIndices.end()) {
+        computeMomentArms(s);
+        return getCacheVariableValue<SimTK::Vector>(s, MOMENT_ARMS_NAME)
+                .get(_coordinateIndices.at(coord.getAbsolutePathString()));
+    } else { 
+        return 0.0; 
+    }
 }
 
 double FunctionBasedPath::getLengtheningSpeed(const SimTK::State& s) const 

diff --git a/OpenSim/Simulation/Model/FunctionBasedPath.h b/OpenSim/Simulation/Model/FunctionBasedPath.h
@@ -193,6 +193,10 @@ OpenSim_DECLARE_CONCRETE_OBJECT(FunctionBasedPath, AbstractPath);
     // ABSTRACT PATH INTERFACE
     double getLength(const SimTK::State& s) const override;
     double getLengtheningSpeed(const SimTK::State& s) const override;
+    /// @note This must check if the path is dependent on the provided 
+    /// coordinate, which requires a search through the list of coordinates.
+    /// To retreive the moment arms directly from the cache variable, use
+    /// `getMomentArms()`.
     double computeMomentArm(const SimTK::State& s, 
             const Coordinate& coord) const override;
     void addInEquivalentForces(const SimTK::State& state,