Address review

Delete meshes and update example accordingly.
Return empty vector if a wrong frame is requested.
Use the appropiate invalid frame index.
Erase commented line not used in mat4x4vec.i.

bindings/matlab/matlab_mat4x4vec.i

@@ -26,7 +26,7 @@
                     d[overall_index]=content[index_sequence];
                 }
             }
-            //free(content); //Tried to free the pointer but got error.
+
             ++it;
         }
 

examples/iDynTreeWrappers/visualizeRobot.m

@@ -1,29 +1,26 @@
 %% This script is an example on how to use the matlab iDynTree visualization
-%%      Launch this file from the folder it is contained
-currentFolder=pwd;
-% insert the path where the meshes may be found, it replaces what is required
+% To use insert the path where the meshes may be found, it replaces what is required
 % to complete the path inside the urdf visual mesh field.
 
 % Example: 
-% The test model has the following mesh file in the URDF
+% If a test model has the following mesh file in the URDF
 % 'package://stl/sim_sea_2-5_root_link_prt-binary.stl'
-% The required file is inside the meshes folder in this directory,
-% so to complete the path we are missing meshes as a prefix to the full
-% path starting from this directory.
-meshFilePrefix='meshes/';
-% The model is in this same folder
-modelPath=[currentFolder '/'];
-fileName='model_uses_stl.urdf';
+% The required path is what it takes to reach the stl folder.
+% meshFilePrefix=<path_to_stl_folder>; 
+% It basically replaces the functionality of find Package by inserting the
+% path manually.
+% The path to the model is also required: 
+% modelPath=<path_to_urdf_folder>;
 
 % REMARK : If you have installed the URDF models by https://github.com/robotology/icub-models
 % You could fill the required variables as follows:
 % % Substitute in the following the location of the install prefix of icub-models
-% icubModelsInstallPrefix = "";
-% meshFilePrefix = [icubModelsInstallPrefix '/share']
-% % Select the robot using the folder name
-% robotName=""
-% icubModelPath = [icubModelsInstallPrefix '/share/iCub/robots/' robotName '/']
-% fileName='model.urdf';
+ icubModelsInstallPrefix = [getenv('ROBOTOLOGY_SUPERBUILD_SOURCE_DIR') '/build-linux/install/'];
+ meshFilePrefix = [icubModelsInstallPrefix '/share'];
+% Select the robot using the folder name
+ robotName='iCubGenova04';
+ modelPath = [icubModelsInstallPrefix '/share/iCub/robots/' robotName '/'];
+ fileName='model.urdf';
 
 jointOrder={
     'r_hip_pitch';

src/high-level/src/KinDynComputations.cpp

@@ -889,12 +889,12 @@ Transform KinDynComputations::getRelativeTransform(const std::string& refFrameNa
 {
     int refFrameIndex = getFrameIndex(refFrameName);
     int frameIndex = getFrameIndex(frameName);
-    if( frameIndex < 0 )
+    if( frameIndex == iDynTree::FRAME_INVALID_INDEX )
     {
         reportError("KinDynComputations","getRelativeTransform","unknown frameName");
         return Transform::Identity();
     }
-    else if( refFrameIndex < 0 )
+    else if( refFrameIndex == iDynTree::FRAME_INVALID_INDEX )
     {
         reportError("KinDynComputations","getRelativeTransform","unknown refFrameName");
         return Transform::Identity();
@@ -1005,7 +1005,7 @@ Transform KinDynComputations::getRelativeTransformExplicit(const iDynTree::Frame
 Transform KinDynComputations::getWorldTransform(std::string frameName)
 {
     int frameIndex = getFrameIndex(frameName);
-    if( frameIndex < 0 )
+    if( frameIndex  == iDynTree::FRAME_INVALID_INDEX )
     {
         return Transform::Identity();
     }
@@ -1081,10 +1081,10 @@ std::vector<iDynTree::Matrix4x4> KinDynComputations::getWorldTransformsAsHomogen
     {
         std::string frameName=frameNames[number];
         int frameIndex = getFrameIndex(frameName);
-        if( frameIndex < 0 )
+        if( frameIndex  == iDynTree::FRAME_INVALID_INDEX )
         {
-            reportError("KinDynComputations","getWorldTransformsAsHomogeneous", "requested frameName not found in model");
-            worldTransforms.push_back(Transform::Identity().asHomogeneousTransform());
+            reportError("KinDynComputations","getWorldTransformsAsHomogeneous", "requested frameName not found in model. Returning empty vector.");
+            return {};
         }
         else
         {