Sdk

[dcnieho]

Dear Farshizzo,

Looking at the code more (and the C++ implementation of viz:ata), is it true that it is possible to pass an arbitrary number of arguments (with arbitrary names and somewhat arbitrary datatypes) through the Python interface to the C++ extension code? That's great! But how would one go about that at the Python side? Hmm, looking at the code in viz.VizExtensionNode and viz.VizExtension maybe its not possible yet). Anyway, that would be very cool! I do see I am able to pass back to Python arbitrary data structures (because lists and such are supported! and with some hacking any other Python datatype i see)

Another question is how to set error conditions in the C++ code and communicate them to the Python code? In the old code, one could say ((VizCustomNodeObj*)custom)->status = 0; in some functions (but not CommandCustomNode sadly) which would cause Vizard to communicate an error ocurred. Is it possible through the interface defined in pyerrors.h? If something is possible, could you add an example?

Lastly, I'm happy to see the void MyExtension::update(const viz::Event &e) function, that seems useful! Some questions though:
1) From inside this function, is it possible to retrieve pointers to the Nodes/Sensors/Textures attached to the extension to perform operations on them and/or pass data along?
2) I see that the viz::Event object has function for getting the X, Y and Z input arguments, amongst others. How are these set?
3) related to that, is it possible to override the update call from Python? I'd like to define my own function to run every frame (I now do that using vizact.ontimer(0,self.stim.update), where self.stim.update is a function i defined) where it does some processing and then passes some data along to the plugin. If you answer to 1) is no, I guess I'll keep doing what I'm doing now?

Thank you for the answers!
Best,
Dee

[dcnieho]

Dear Farshizzo,

I did run into some trouble. My C++ also uses boost, and I get a whole bunch of redefinition warnings for boost::any.

My version of boost (as does the current trunk version) apparently defines #define BOOST_ANY_INCLUDED instead of #define BOOST_ANY_HPP, leading to this situation.

Could you also add the other define to your custom header or is there a more appropriate way for me or you to deal with this?

Best,
Dee

[farshizzo]

Originally Posted by dcnieho

Could you also add the other define to your custom header or is there a more appropriate way for me or you to deal with this?

Thanks, we'll modify the included header so it doesn't conflict with boost.

[farshizzo]

Originally Posted by dcnieho

Looking at the code more (and the C++ implementation of viz::Data), is it true that it is possible to pass an arbitrary number of arguments (with arbitrary names and somewhat arbitrary datatypes) through the Python interface to the C++ extension code? That's great! But how would one go about that at the Python side? Hmm, looking at the code in viz.VizExtensionNode and viz.VizExtension maybe its not possible yet). Anyway, that would be very cool! I do see I am able to pass back to Python arbitrary data structures (because lists and such are supported! and with some hacking any other Python datatype i see)

That was the idea with the viz::Data structure. Currently you are limited to passing the fixed arguments through the Python interface though. Eventually we would like to expose the ability to pass more complex data types through Python.

Originally Posted by dcnieho

Another question is how to set error conditions in the C++ code and communicate them to the Python code? In the old code, one could say ((VizCustomNodeObj*)custom)->status = 0; in some functions (but not CommandCustomNode sadly) which would cause Vizard to communicate an error ocurred. Is it possible through the interface defined in pyerrors.h? If something is possible, could you add an example?

The new interface allows you to return arbitrary Python objects from the command method, so you can return anything you wish to signal an error. If you want to raise a Python exception from your plugin, then you can use the Python PyErr_SetString function to raise an exception.

Originally Posted by dcnieho

1) From inside this function, is it possible to retrieve pointers to the Nodes/Sensors/Textures attached to the extension to perform operations on them and/or pass data along?

No, but you can internally save a reference to them. This is what most of the built-in plugins do. For example, the extension class can keep a list of sensor objects created by it:

std::list< viz::ref_ptr< MySensor > > m_sensors;

Originally Posted by dcnieho

2) I see that the viz::Event object has function for getting the X, Y and Z input arguments, amongst others. How are these set?

The viz::Event object passed to the plugins only provides the frame information described in the docs. The X, Y, Z arguments are not used for update events.

Originally Posted by dcnieho

3) related to that, is it possible to override the update call from Python? I'd like to define my own function to run every frame (I now do that using vizact.ontimer(0,self.stim.update), where self.stim.update is a function i defined) where it does some processing and then passes some data along to the plugin. If you answer to 1) is no, I guess I'll keep doing what I'm doing now?

If you want Python code to run every frame, then you can use the existing Python methods of registering an update function. You can also call methods of the extensions Python interface from within the C++ code. For example, if you added a method called myupdate to the extension Python interface, then the following code could be used to call it:

PYTHON_BEGIN_RUN_CODE
  PyObject *pyExt = Python_GetExtensionObject(GetID());
  if(pyExt) {
    PyObject *pyReturn = PyObject_CallMethod(pyExt,"myupdate");
    PYTHON_FLUSHERROR;
    Py_XDECREF(pyReturn);
    Py_DECREF(pyExt);
  }
PYTHON_END_RUN_CODE

[dcnieho]

Hi Farshizzo,

Thank you for all the detailed information! I still have some questions though:

Originally Posted by farshizzo

No, but you can internally save a reference to them. This is what most of the built-in plugins do. For example, the extension class can keep a list of sensor objects created by it:

std::list< viz::ref_ptr< MySensor > > m_sensors;

Is this supposed to be

std::list< osg::ref_ptr< MySensor > > m_sensors;

instead? I don't seem to have a viz::ref_ptr (but do have a viz::Referenced*). In any case, things seem to work fine with osg::ref_ptr

Originally Posted by farshizzo

The new interface allows you to return arbitrary Python objects from the command method, so you can return anything you wish to signal an error. If you want to raise a Python exception from your plugin, then you can use the Python PyErr_SetString function to raise an exception.

I am trying the Python PyErr_SetString method and I'm having some trouble with it. If I do a normal (non-debug) run and raise/set an error in my plugin, an error occurs on the next command call in the python node class that interfaces with the C++ node instance:

Traceback (most recent call last):
  File "<string>", line 11, in <module>
  File "C:\dat\C\projects\Vizard dll\testCustomNode.py", line 58, in <module>
    stim.setStimSpec('GDcl')
  File "DNstimuli.py", line 45, in setStimSpec
    self.command(1,stimSpec)
  File "C:\Program Files\WorldViz\Vizard4\python\viz.py", line 6837, in command
    return _ipcSend(_VIZ_CMDEXTNODE,self.id,command,mesg,x,y,z,w)
TypeError: command must be an int

The line self.command(1,stimSpec) is the first command I sent to the node after the command in which the exception was raised (which created no output or anything when raised), there can be any amount of code in between these two calls.

If setup a debug breakpoint on this first call after the raised exception (self.command(1,stimSpec)), and try to step into it, i get this output:

C:\Program Files\WorldViz\Vizard4\python\vizbdb.py:410: RuntimeWarning: tp_compare didn't return -1 or -2 for exception
  if id in ids:
Traceback (most recent call last):
  File "<string>", line 11, in <module>
  File "C:\dat\C\projects\Vizard dll\testCustomNode.py", line 58, in <module>
    stim.setStimSpec('GDcl')
  File "DNstimuli.py", line 45, in setStimSpec
    self.command(1,stimSpec)
  File "DNstimuli.py", line 45, in setStimSpec
    self.command(1,stimSpec)
  File "C:\Program Files\WorldViz\Vizard4\python\vizbdb.py", line 254, in trace_debug
    self.wait_for_input(frame,None)
  File "C:\Program Files\WorldViz\Vizard4\python\vizbdb.py", line 436, in wait_for_input
    id,data = self.wait_for_message(_INPUT_MESSAGES)
  File "C:\Program Files\WorldViz\Vizard4\python\vizbdb.py", line 410, in wait_for_message
    if id in ids:
RuntimeError: testing

The good part here is that "RuntimeError: testing" is what I am throwing from the C++ code (PyErr_SetString(PyExc_RuntimeError, "testing");)

Other things I tried:
- doing data.set( PYTHON_RETURN_OBJECT, PYTHON_INT(-1)); or data.set(PYTHON_RETURN_OBJECT, NULL); after the call to PyErr_SetString did not help (inspired by some reading of how error states should be communicated from Python).
- try/except around the call where the exception is raised. This didn't do anything, as expected when the exception goes unnoticed.

What am I missing? Thanks for your help!

[farshizzo]

Originally Posted by dcnieho

Is this supposed to be

std::list< osg::ref_ptr< MySensor > > m_sensors;

instead? I don't seem to have a viz::ref_ptr (but do have a viz::Referenced*). In any case, things seem to work fine with osg::ref_ptr

The viz::ref_ptr usage was intentional. You need to #include <viz/ref_ptr> which should come with the SDK.

Originally Posted by dcnieho

Other things I tried:
- doing data.set( PYTHON_RETURN_OBJECT, PYTHON_INT(-1)); or data.set(PYTHON_RETURN_OBJECT, NULL); after the call to PyErr_SetString did not help (inspired by some reading of how error states should be communicated from Python).
- try/except around the call where the exception is raised. This didn't do anything, as expected when the exception goes unnoticed.

What am I missing? Thanks for your help!

You should have to set NULL as the return object. However, I just noticed that Vizard is eating up the exception if NULL is returned by the plugin. We'll need to fix this for the next release. In the meantime I would just raise the exception from the Python wrapper method.

[dcnieho]

Originally Posted by farshizzo

The viz::ref_ptr usage was intentional. You need to #include <viz/ref_ptr> which should come with the SDK.

You should have to set NULL as the return object. However, I just noticed that Vizard is eating up the exception if NULL is returned by the plugin. We'll need to fix this for the next release. In the meantime I would just raise the exception from the Python wrapper method.

Sorry to dig up an old thread, but i am just testing this again with the newest Vizard 4 and SDK (both freshly downloaded today).

When try to send an exception from my python plugin as follows

PyErr_SetString(PyExc_RuntimeError, "errorstring");
data.set( PYTHON_RETURN_OBJECT, NULL);

I always get a TypeError instead of the exception i'm trying to communicate. The stacktrace always ends like this:

  File "C:\Program Files (x86)\WorldViz\Vizard4\python\viz.py", line 7381, in command
    return _ipcSend(_VIZ_CMDEXTNODE,self.id,command,mesg,x,y,z,w)
TypeError: command must be an int

The next call above that is me calling the C++ code from the extension node, e.g. self.command(1,stimSpec) (my node derives from viz.VizExtensionNode)

I'm not sure what this typeerror is referring to, as my command is correct, it works without error when not trying to return an exception.

Am I doing something wrong?

Best and thanks,
Dee

[farshizzo]

Can you post the full traceback? It looks like you are using passing an invalid parameter to the command method. As the traceback says, the first argument must be an int, and you are most likely passing some other type.