[SOLVED] How to add python script to c++ code

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  • 21 June 2017 at 19:44 #9342
    Yannie
    Blocked

    Hello All,

    I’m learning to write scene in C++, and would like to use the python keyboard control script in it, any example code to show how to do this?

    I tried to define a PythonScriptController pointer, but when I ran the code, it always show an error:

    
Unhandled exception at 0x000000001E08BF77 (python27.dll) in test.exe: 0xC0000005: Access violation reading location 0xFFFFFFFFFFFFFFFF.

    Thank you!

    23 June 2017 at 17:42 #9348
    Hugo
    Keymaster

    Hi Yannie,

    To use Python scripts in a simulation written in C++, indeed, you need to do is to instantiate the C++ class PythonScriptController. Your C++ application must therefore have a dependency on the SofaPython plugin (explicit in CMakeList.txt).
    HTH,

    Hugo

    24 June 2017 at 05:15 #9356
    Yannie
    Blocked

    Thanks Hugo for the reply.

    I did add sofaPython plugin. But it always gives the above error. It looks the the pythonscriptcontroller instance can’t read in the .py file.

    Here is my code:

    
const char* filename = “keyboardControl.py”;
sofa::component::controller::PythonScriptController::SPtr pyContr = sofa::core::objectmodel::New<sofa::component::controller::PythonScriptController>();
pyContr->m_filename.setValue(filename);

    I suppose the class can parse the .py file automatically once it read in?

    24 June 2017 at 15:29 #9357
    Hugo
    Keymaster

    Hey Yannie,

    the error shows that you are using an un-initialized data. But your code looks ok. I would have written : 

    
#include "PythonScriptController.h"

...

int main(int argc, char** argv)
{

...

sofa::simulation::Node::SPtr groot = sofa::simulation::getSimulation()->createNewGraph("root");
groot->setGravity( Coord3(0,-10,0) );

...

std::string filename = "keyboardControl.py";
std::string classname = "yourclassname";
sofa::component::controller::PythonScriptController::SPtr pyContr = sofa::core::objectmodel::New<sofa::component::controller::PythonScriptController>();
pyContr->m_filename.setValue(filename);
pyContr->m_classname.setValue(classname);
groot->addObject(pyContr);
}

    and your CMakeLists.txt should look like:

    
cmake_minimum_required(VERSION 3.1)
project(mytest)

find_package(SofaSimulation)
find_package(SofaPython)

add_executable(${PROJECT_NAME} test.cpp)
target_link_libraries(${PROJECT_NAME} SofaPython SofaSimulation)

    HTH,

    Hugo

    30 June 2017 at 22:53 #9547
    Yannie
    Blocked

    Thanks Hugo!
    I’ve play around a bit, it still has this problem, I’m able to locate where the error come but not sure how to solve it. So the code run into the python error at this line:

    sofa::simulation::getSimulation()->init(groot.get());

    And I can trace it to PythonScriptController::script_initGraph(Node *node), it gave the exception at here.

    Does it has something to do with the m_classname? I assume it should be the classname in Python script. Then I tried to just type some simple code in python, like

    def createScene(node):

    def hello():
        print 'hello !'

    But still, no luck.
    Any thoughts? Thanks!

    1 July 2017 at 00:25 #9595
    Hugo
    Keymaster

    Hi Yannie

    Could you please post the complete Python script ? Python scripts are sensitive to tabulations. Seeing the entire script would help,

    Thank you !

    1 July 2017 at 03:22 #9596
    Yannie
    Blocked

    The script I posted above is the whole script. For this script, I didn’t add m_classname as there is no class name in it.

    I also tried the PythonScriptController_Placeholders.py in the sofaPython examples folder and set the m_classname to ExampleController, same problem!

    Thanks!

    10 July 2017 at 14:21 #9782
    Hugo
    Keymaster

    Hi Yannie,

    You tried PythonScriptController_Placeholders.py in your C++ scene and it did not work ?
    In your C++ scene, you instantiated a PythonScripController with the data filename set to PythonScriptController_Placeholders.py and the data classname set to the string ExampleController ?

    Have you tried to specify in you C++ scene, a RequiredPlugin with the data pluginName set to SofaPython ?

    HTH

    Hugo

    17 July 2017 at 22:17 #9797
    Yannie
    Blocked

    Thanks Hugo,

    Well, I debugged for some time and found that the PythonScripController.cpp constructor doesn’t call loadscript(), so I write add a new constructor and rebuilt sofaPython and it worked. I seems that the PythonScripController was written for use cases that read scene files instead of constructor the object in code, because it does work if I just load the .scn file for runsofa. I could be wrong as I don’t know the platform well enough. Does it work for you if you just assign filename and classname?

    Additional question. So I tried the keyboardcontrol.py again, but my object doesn’t move and the error is mechanicalState.free_position index out range. And I print out free_position, it is empty, when and where this free_position is initiated?

    Thanks again!
    Yannie

    19 July 2017 at 14:27 #9805
    Hugo
    Keymaster

    Dear Yannie,

    Your question has been discussed at the weekly dev meeting (you can follow the agenda and report by subscribing to the sofa-dev mailing list).
    Here is the answer I got:

    • a question on the forum about SofaPython in a C++ scene: the best is to initialize the python environment using the PluginManager (sofa::helper::system::PluginManager). Thus, you are able to directly load the python environment
    • about the initialization of free_position (in the MultiVector of the MechanicalState), it is created when a FreeAnimationLoop is created if I remember properly. Otherwise, it won’t be allocated.

      • HTH
      Best,

      Hugo

    25 July 2017 at 23:34 #9853
    Yannie
    Blocked

    Thanks Hugo!

    I did use the PluginManager to load the SofaPython as well as adding RequiredPlugin node, not sure why it didn’t call loadscript with that setting.

    Thanks, the FreeMotionAnimationLoop does help, now I can move object around!

    Best,
    Yannie

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