fix load issue with scale tool (#3110)

* fix load issue scale tool load issue if model or marker set file is given as an absolute path, and the tool was created from a setup file. update error message to better reflect possible issues.

* update CHANGELOG

CHANGELOG.md

@@ -8,6 +8,7 @@ This is not a comprehensive list of changes but rather a hand-curated collection
 v4.4
 ====
 - Updated ezc3d to version 1.4.6 which better manage the events defined in a c3d file.
+- Fixed an issue that could happen sometimes with ScaleTool where loading the model file or marker set file could fail if the file was given as an absolute path (Issue #3109, PR #3110)
 
 v4.3
 ====

OpenSim/Tools/GenericModelMaker.cpp

@@ -159,13 +159,17 @@ Model* GenericModelMaker::processModel(const string& aPathToSubject) const
 
     try
     {
-        model = new Model(aPathToSubject + _fileName);
+        std::string modelPath = 
+            SimTK::Pathname::getAbsolutePathnameUsingSpecifiedWorkingDirectory(aPathToSubject, _fileName);
+        model = new Model(modelPath);
         model->initSystem();
 
         if (!_markerSetFileNameProp.getValueIsDefault() && _markerSetFileName !="Unassigned") {
             log_info("Loading marker set from '{}'.", 
                 aPathToSubject + _markerSetFileName);
-            MarkerSet *markerSet = new MarkerSet(aPathToSubject + _markerSetFileName);
+            std::string markerSetPath = 
+                SimTK::Pathname::getAbsolutePathnameUsingSpecifiedWorkingDirectory(aPathToSubject, _markerSetFileName);
+            MarkerSet *markerSet = new MarkerSet(markerSetPath);
             model->updateMarkerSet(*markerSet);
         }
     }

OpenSim/Tools/ScaleTool.cpp

@@ -232,8 +232,11 @@ Model* ScaleTool::createModel() const
         Model *model = getGenericModelMaker().processModel(_pathToSubject);
         if (!model)
         {
-            log_error("Unable to load generic model at path {}.", 
-                _pathToSubject);
+            // processModel() attempts to load both the model and market set
+            // file. _pathToSubject might be misleading of model path was
+            // given as an aboslute path in the setup file, so it was
+            // removed from this error message.
+            log_error("Unable to load the generic model or marker set file.");
             return 0;
         }
         else {