This chapter aims at developers who want to extend Vortex with more functionality or communicate from Vortex to and from an external system.

About Plugins

Vortex plugins allow developers to add more functionality to Vortex. Functionality is added by Extensions and Modules.
Extensions add features to content: They are mostly data containers with an implementation known by a module.
Modules control an aspect of the simulation. They consume the extensions' data and provide behaviour.
When an extension is used by a module, it is said that the extension is managed by that Module and is considered active.

Extensions and Modules are packaged in plugins. Vortex Studio provides multiples plugins and the Vortex Studio SDK allows users to create their own and extend Vortex.

Making a plugin

Technically speaking, plugins are actually dynamics libraries with a 'vxp' extension publishing specific interfaces to allow the plugin manager to gather information and instantiate modules and extensions.

Vortex Studio will load these .vxp and will invoke the following methods, which must be implemented:

#ifdef _MSC_VER
#define SYMBOL __declspec(dllexport)
#else
#define SYMBOL
#endif
 
extern "C" SYMBOL bool GetPluginInfo(VxPluginSystem::VxPluginInfo & pluginInfo)
{
    pluginInfo.setDisplayName("My Plugin Name");
    pluginInfo.setVendor("My Vendor Name");
    pluginInfo.setDescription("A description of my plugin");
    return true;
}

extern "C" SYMBOL bool InitializePlugin(VxPluginSystem::VxPluginManager & pluginManager, int /*unused*/, char ** /*unused*/, std::string * /*unused*/)
{
    return VxSim::VxExtensionFactory::registerType<MyExtension>(MyExtension::kFactoryKey, pluginManager.getCurrentVXP());
}

extern "C" SYMBOL bool UninitializePlugin(VxPluginSystem::VxPluginManager & pluginManager, std::string * /*unused*/)
{
    return VxSim::VxExtensionFactory::unregisterType(MyExtension::kFactoryKey);
}

• GetPluginInfo
  • Used by the plugin manager to collect information on the plugin so that it can be displayed e.g. in a selection page of the Editor.
• InitializePlugin
  • Called by the plugin manager to give the opportunity to the plugin to register its modules and extensions to the extension factory.
• UninitializePlugin
  
  • Called by the plugin manager when unloading the plugin. Extensions and modules should be unregistered from the extension factory.

Extensions and Modules

Extensions are first-class objects of Vortex. In Vortex Studio, everything you see in the Editor is an extension: scenes, parts, graphics galleries, graphic nodes and materials, source and listeners, Python scripts, etc.
Objects added to the Setup are also extensions; modules are also extensions. The setup itself is an extension.

Knowing how to create extensions is essential for extending Vortex. An extension is a C++ class that implements the IExtension interface and some other interfaces depending on the target functionality.
An extension is defined by its factory key and the interface it implements. Its data are called fields.

Factory Key

Each object is characterized by a factory key. A factory key uniquely defines a type of extension with a universally unique identifier (UUID).
The UUID is simply a 128-bit value that shall never change once the extension is used in content: it will be used when any content is persisted.
Several tools can be used to generate a UUID (e.g. Visual Studio). 

The factory key also has additional members that help to define the extension with human-readable information.

/// Information that allow access to a plugin through the VxExtensionFactory
///
class VxFactoryKey
{
public:
    /// UUID for this key
    ///
    VxUuid uuid;
    /// Category name
    ///
    std::string categoryName;
    /// Feature name
    ///
    std::string featureName;
    /// VXP, or DLL, file name if applicable without the extension
    ///
    std::string vxpName;
};

• uuid: Unique identifier of the extension
• Category Name: Category for the extension. Used for display in the editor as the category. However, all modules are bundled under modules no matter the category
  • 
• Feature Name: Type of the extensions. This name appears in the editor in the toolbox
• vxpname: Name of the vxp having this extension. When the factory creates an extension, it will look up this name and try to find the file having this name plus the extension ".vxp".

The factory key can be created locally when registering the extension in the plugin. However, the key is also useful when creating or filtering from outside of the plugin so the SDK often published the key in a header.

The example below is the factory key of the dynamics module (called Engine). The module can be loaded from the plugin VxDynamicsPlugin.vxp located in <your CM-Labs installation folder>/plugins

/// Factory Key for the VxDynamicsModule
///
const VxSim::VxFactoryKey kFactoryKey(VxSim::VxUuid("{3a6c7474-6a01-5f06-ac36-c3a0d7cad4bf}"), "Dynamics", "Engine", "VxDynamicsPlugin");

Extension Interface

There are three major types of extensions. Any extension must derive from one and only one of these interfaces:

• VxSim::IExtension: an extension that adds features to content (mechanism, scene) or to the application.
• VxSim::IObject: an object that has the same features as IExtension, but can also have child extensions (useful to create more complex systems for content).
• VxSim::ISimulatorModule: a module manages certain types of extensions and calls their methods at the appropriate moment during the application update. Modules can only be added to a VxApplication or ApplicationConfig.

The interface will be called at the appropriate moment by Vortex to achieve the desired functionality.

IExtension Interface

IExtension is the most basic interface for extensions. It is necessary to support basic functionalities of Vortex Toolkit such as serialization, network, and keyframes.
It should generally be used when implementing simple extensions. The extension's data is contained in VxSim::VxExtension that can be obtained with getProxy().

IExtension has a single constructor:

IExtension::IExtension(VxSim::VxExtension* proxy, int version = 0);

It must be used by all extensions. The proxy will be provided by VxExtensionFactory but the version needs to be provided by the actual implementation. Versioning will be used when loading and saving the extension.

The constructor of an extension always has the following basic form:

const int kCurrentVersion = 20210315; 

class MyExtension : public VxSim::IExtension 
{ 
	public: 
		MyExtension(VxSim::VxExtension* proxy) 
			: VxSim::IExtension(proxy, kCurrentVersion) 
		{ 
		} 
};

Application Context

An extension has access to some information about the application, notably the application mode, the current frame, and additional services. See Vortex Studio SDK Advanced - Integrating the Application

Active and Inactive extension

When a module has accepted to manages an extension, the extension itself will be notified with the callback IExtension::onActive().
This method is a good point to initialize your extension, create internal data and register your observers.
An active extension will have its observers called and will be processed by its module. An inactive extension will not be invoked. For example, a dynamics extension is active on the master node and inactive on the slave node. Its data is only processed on the master.
When a module is done with an extension, the extension itself will be notified with the callback IExtension::onInactive(). This method is a good point to clean up your extension, generally undoing what was done in onActive().

Each method will be called the same number of times. It is not impossible that an extension becomes active, then inactive during loading, as some features can remove or disable extensions from the content loaded.
See below, onExtensionAdded and onExtensionRemoved for the module equivalent.

IObject Interface

IObject is an extended version of IExtension. In addition to all the functionalities of IExtension, it adds support for sub-extensions. It is generally used when implementing complex extension systems.
The object's data is contained in VxSim::VxObject that can be obtained via the getProxy() method.

IObject has a single constructor, that is similar to the constructor of IExtension.

IObject::IObject(VxSim::VxObject* proxy, int version = 0);

It must be used by all objects. The proxy will be provided by the VxExtensionFactory but the version needs to be provided by the actual implementation. Versioning will be used when loading and saving the object.

The constructor of an object always have this basic form:

const int kCurrentVersion = 20210315; 

class MyObject : public VxSim::IObject 
{ 
    public: MyObject (VxSim::VxObject* proxy) 
        : VxSim::IObject(proxy, kCurrentVersion) 
    { 
    } 
};

Additional Interfaces for Extensions

In addition to IExtension or IObject, an extension usually implements one or several interfaces. The choice of the interface depends on the desired functionality. The following is a list of useful interfaces with the modules that manages them.

Functionalities

Behaviour Modifiers

ISimulatorModule interface

An ISimulatorModule is a special kind of extension that can only be added to VxApplication (with VxApplication::insertModule) or to ApplicationConfig.
When implemented, it will be contained in a VxSim::VxSimulatorModule that is returned with getProxy().
A module will manage its extensions and execute at each update either code based on their data or callbacks on their implementation.
If you develop an extension already based on a predefined interface, e.g. IDynamics, a module will be already available and you won't need to develop your own.
If you develop an extension based on a new interface, e.g. your own device, you will need to also code a module to manage the extensions of that type.

ISimulatorModule has two constructors, that are similar to the constructor of IExtension.

ISimulatorModule::ISimulatorModule(VxSim::VxSimulatorModule* proxy, int version = 0); 
ISimulatorModule::ISimulatorModule(VxSim::VxSimulatorModule *proxy, int preUpdatePriority, int updatePriority, int postUpdatePriority, int version = 0);

The proxy will be provided by the VxExtensionFactory but the version needs to be provided by the actual implementation. Versioning will be used when loading and saving the module.
The priorities can also be given to the constructor; they control the order in which the VxApplication calls onPreUdpate(), onUpdate() and onPostUpdate() on all its modules.

The constructor of a module usually has this basic form:

const int kCurrentVersion = 20210315; 

class MyModule: public VxSim::ISimulatorModule 
{ 
    public: MyObject (VxSim::VxSimulatorModule * proxy) 
        : VxSim::ISimulatorModule(proxy, kCurrentVersion) 
    { 
    } 
};

Extension Management Support

The VxApplication notifies all ISimulatorModule of all extensions that are added to it through the VxSim::ISimulatorModule::onExtensionAdded() method. It is there that each ISimulatorModule decides if it will manage the new extension or not.
Typically a module validates if it will accept the extension and call VxSim::ISimulatorModule::_addManagedExtension(). When an extension is added to a module, the extension's callback VxSim::IExtension:::OnActive() will be called.
Likewise, when an extension is removed from the application, it will call the VxSim::ISimulatorModule::onExtensionRemoved() method. If the module accepted the extension when it was added, it must call  VxSim::ISimulatorModule::_removeManagedExtension().
When an extension is removed from a module, the extension's callback VxSim::IExtension:::OnInactive() will be called.

Each method will be called the same number of times. It is not impossible that an extension will be added, then removed during loading, as some features can remove or disable extensions from the content loaded.

Example

The module MyModule needs to manage all MyExtension instances that are put in the content.

const int kCurrentVersion = 20210315; 

class MyModule : public VxSim::ISimulatorModule 
{ 
    void _prepareExtension(VxSim::VxSmartInterface<MyExtension> my); 
    void _cleanupExtension(VxSim::VxSmartInterface<MyExtension> my); 

public: 
    MyModule(VxSim::VxSimulatorModule* proxy) 
        : VxSim::ISimulatorModule(proxy, kCurrentVersion ) 
    { 
    }
 
    virtual void onExtensionAdded(VxSim::VxExtension* extension) 
    { 
        VxSim::VxSmartInterface<MyExtension> my = extension; 

        if (my.valid()) 
        { 
            _addManagedExtension(extension); 
            _prepareExtension(my); 
        } 
    } 

    virtual void onExtensionRemoved(VxSim::VxExtension* extension) 
    { 
        VxSim::VxSmartInterface<MyExtension> my = extension; 
        if (my.valid()) 
        { 
            _cleanupExtension(my); 
            _removeManagedExtension(extension); 
        } 
    } 
};

Simulation Management Support

Several methods can be overridden to implement an ISimulatorModule-specific functionality.

Initialization and cleanup

virtual void VxSim::ISimulatorModule::onAddToApplication(VxApplication* application); 
virtual void VxSim::ISimulatorModule::onRemoveFromApplication(VxApplication* application);

onAddToApplication() is called just after the ISimulatorModule is added to the VxApplication.

This is the right moment to perform any initialization required by the module: starting a thread, connecting to a network socket, loading some internal data, etc. This is usually done very early in the application start-up, but will not be done when building an ApplicationConfig. Any initialization that was done must be undone in onRemoveFromApplication.

Updates

virtual void VxSim::ISimulatorModule::onPreUpdate(VxSim::eApplicationMode mode); 
virtual void VxSim::ISimulatorModule::onUpdate(VxSim::eApplicationMode mode); 
virtual void VxSim::ISimulatorModule::onPostUpdate(VxSim::eApplicationMode mode); 
void VxSim::ISimulatorModule::_sortManagedExtensions();

Those methods are the heartbeat of the simulation. They are called in the VxApplication::update() loop. This is where you want to do the work that the module is designed to do. onPreUdpate is called before the dynamics, onPostUpdate is called after the dynamics but before the graphics. onUpdate is called in between the two. Generally, onUpdate is not used. All those methods receive the current application mode of the VxApplication.

_sortManagedExtensions() will make sure that the managed extensions are sorted according to their dependency as given by the connection layout.

class MyExtension : public VxSim::IExtension 
{ 
   [...] 

    void doOneStep(); 
}; 

class MyModule : public VxSim::ISimulatorModule 
{ 
    [...] 

    virtual void onPreUpdate(VxSim::eApplicationMode mode) 
    { 
         if ( mode == VxSim::kModeSimulating ) 
         { 
             // make sure that the extension are sorted according to the connection graph layout 
             // if already sorted, no time is spent here _sortManagedExtensions(); 
             auto& extensions = getProxy()->getManagedExtensions(); 
             for (auto it = extensions.begin(); it != extensions.end(); ++it) 
             { 
                 VxSim::VxSmartInterface<MyExtension> my = *it; 
                 my->doOneStep(); 
             } 
         } 
    } 
};

Application Mode

 virtual void VxSim::ISimulatorModule::onApplicationModeChange(VxSim::eApplicationMode previous, VxSim::eApplicationMode current);

onApplicationModeChange is called whenever the mode of the VxApplication is changing. It will be called right before the mode actually changes.
Use this callback to do any special processing necessary when transitioning from one mode to another.

Helper Functions

ISimulatorModule has a few helper functions:

• getProxy() gives access to the main Vortex Toolkit object that carries the data and implementation of the ISimulatorModule.
• getApplication() gives access to the VxApplication that contains the module.

Deploying Your Plugin

Your vxp file can reside anywhere on your file system. Typically, Vortex searches for vxp in its plugins folder and dll in its bin folder. 
In order to add search locations, the Vortex Editor options, and your application setup file (including the player for example), must be edited to find and load your plugin.
You can put your library files alongside your plugin file, Vortex will find them.

Vortex Studio Editor

• Launch the Vortex Studio Editor.
• Go to Options.
• Go to the setup section.
• Add your Plugin paths using the widget.
• Save, you will be prompted to restart the editor.
• 
• Note the editor.vxc does not need to be modified.

Simulator Application

• Launch the Vortex Studio Editor.
• Open your setup file.
• In the Explorer, select the root of your setup file.
• In the Property view, expand the PluginDirectories field.
• Use the widget to increase the size.
• Click on the ... button and select your folder.
• Save your setup file.
• 

Extension Data

Inputs, Outputs and Parameters

The extension data is stored in VxData::Field<T> of the appropriate type. The use of fields gives us a high level of standardization, which simplifies Vortex Toolkit and improves overall performance. 

There are three major field containers in every extension: inputs, outputs and parameters.

• Inputs: data that is fed to the extension. It can change anytime in the simulation.
• Outputs: data produced by the extension. Outputs of one extension can be connected to inputs of another extension.
• Parameters: constant data in the simulation. It can be changed while editing the object, but not during the simulation.

All inputs, outputs and parameters in an extension are automatically serialized. They are written to file when saving, and put back in the extension when loaded.

Declaring data

The header file for an extension with three fields (one input, one output, and one parameter) would look like the following:

class MyExtension : public VxSim::IExtension, public VxSim::IDynamics 
{ 
    public: 
        MyExtension(VxSim::VxExtension* proxy); 

        // declaration of the fields 
        VxData::Field<bool> inputEnable; 
        VxData::Field<VxMath::Vector3> outputScaleFactor; 
        VxData::Field<VxDynamics::Part*> parameterTargetPart; 
};

The constructor must declare the name for the fields, whether they are inputs, outputs or parameters and optionally a default value.

MyExtension::MyExtension(VxSim::VxExtension* proxy) 
    : VxSim::IDynamics(proxy) 
    , VxSim::IExtension(proxy, kCurrentVersion) 
    , inputEnable(false, "Enable", &proxy->getInputContainer()) 
    , outputScaleFactor(Math::Vector3(1,1,1), "Scale", &proxy->getOutputContainer()) 
    , parameterTargetPart(nullptr, "Target", &proxy->getParameterContainer()) 
{ 
    outputScaleFactor.setPhysicalDimension(Vx::VxPhysicalDimension::kScale);
    outputScaleFactor.setDescription("The scaling factor that was applied to the target part.");
}

Field<T>

Field Types

Field<T> represents a data value that has a type (from the template parameter), a name (from the constructor), and a value.

Using Field<T> in an extension

Using Field<T> is as simple as using a variable of type T.

To avoid any ambiguity, Field<T> also has the method getValue() and setValue().

class MyExtension : public VxSim::IExtension, public VxSim::IDynamics 
{ 
    public: 
        MyExtension(VxSim::VxExtension* proxy); 

        // declaration of the fields 
        VxData::Field<double> inputScale; 
        VxData::Field<Math::Vector3> outputScaleFactor; 
        VxData::Field<VxDynamics::Part*> parameterTargetPart; 

        [...] 

    private: 
        void _handleScale(double s); 
        inline void _processInput() 
        { 
            // Field<double> is used just like a double 
            if ( inputScale > 0 ) 
            { 
                _handleScale( inputScale ); 
            } 
            else if ( inputScale > 0 ) 
            { 
                _handleScale( -inputScale.getValue() ); 
            } 
        } 

        inline void _processOutput 
        { 
            // Fields with compound values like VxData::Field<Math::Vector3> are used in the same way 
            Math::Vector3 v(inputScale, inputScale, inputScale); 
            outputScaleFactor = v; 
         } 

         inline void _processParameter() 
         { 
             // VxData::Field<VxDynamics::Part*> can be used like a VxDynamics::Part*
             VxDynamics::Part* p = parameterTargetPart; 
             if ( parameterTargetPart != nullptr ) 
             { 
                 parameterTargetPart->resetInertia(); 
              } 
          } 
};

Additional information

See Vortex Studio SDK Advanced - Fields And Extensions for more information about using fields, and IExtension callbacks.
See code tutorials C++ Tutorial 1: Plugins and Devices for extensions and module implementation examples. The code tutorial are located in <your CM-Labs installation folder>/tutorial

Vx::VxSmartPtr and VxSim::VxSmartInterface

Vortex objects are reference-counted via a special smart pointer class, VxSmartPtr<T>. When you need to keep an VxExtension alive, you should keep it in a VxSmartPtr<T>. Vortex internal's system uses those smart pointer to keep extensions alive.
In some rare case, a developer might want to keep a pointer on a VxExtension without increasing the reference count. In this case, a VxWeakPtr<T> should be used. A weak pointer will become invalid when the reference extension is destroyed.

Unless a developer needs to do generic things on extensions, using VxSmartInterface<T> should be favored. A VxSmartInterface<T> is both a VxSmartPtr to the extension and a pointer to the implementation.
When a developer needs to query, test or use a specific interface, the safest, simplest way is to use a VxSmartInterface<T> object. A VxExtension can contain any kind of implementation: extension or module. VxSmartInterface<T> can be used to query for a specific type of interface, if the interface is found, the extension will be referenced (thus will never be deleted) as long as the VxSmartInterface<T> has it. VxSmartInterface<T> can be initialized with a VxExtension*, a VxSmartPtr<VxExtension>, or with any kind of VxSmartInterace<U>. VxSmartInterface<T> also contains its VxExtension via function getExtension().

void doSomethingWithAIMobile(VxSim::VxExtension* extension)
{
	VxSim::VxSmartInterface<VxSim::IMobile> imobile = extension;
	if ( imobile.valid() )  // check if the IMobile interface was found in the extension
	{
		// by using a VxSmartInterface, we are garanteed that extension will not be deleted during the call to _getTheNewPosition()
		imobile->inputLocalTransform = _getTheNewPosition();
 
		// check if there is also the IGraphic interface (in addition to IMobile)
		VxSim::VxSmartInterface<VxGraphics::IGraphic> graphicAndMobile = imobile;
		if ( graphicAndMobile.valid() )
		{
			_doSomethingSpecial(graphicAndMobile);
		}
	}
}

VxWeakInterface<T> is very similar but it does NOT increase the ref-count of the VxExtension. There are very few cases where VxWeakInterface<T>should be used instead of a VxSmartInterface<T>.
The most important exception is when a class needs a member and does NOT want to keep it alive. Basically, you would only use VxWeakInterface<T>, if you would use a VxWeakPtr<VxExtension>.