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Debug Visualization

ProfileZoneManager and ProfileZone


The PhysX profiling system can be customized so that PhysX profiling events can be read and used by the application. This Section describes how to configure and query PhysX SDK profiling events.

Basic Concepts


The basic classes are PxProfileZoneManager and PxProfileZone. PxProfileZone describes an island of profile information, while PxProfileZoneManager is a collection of PxProfileZone instances.

A key concept to PhysX profiling is the event buffer that is managed by each profile zone. The event buffer is an in-memory buffer of event data such as the timestamp at event start/end. To retrieve this event data the buffer must be flushed. Typically, the buffer would be flushed to mark the end of a profile frame. When the buffer is flushed it is sent to all registered clients (PxProfileZoneClient) before it resets so that it may begin recording the next frame of profile events. Parsing the event buffer is performed using a custom handler (PxProfileEventHandler) that parses each event in turn. The classes involved in this procedure shall be introduced in the following Sections.


PxProfileZoneManager is a singleton-like class that serves as a collection of profile zones. PxProfileZoneHandler instances can be registered with PxProfileZoneManager in order to receive an event when a PxProfileZone instance is added or removed. Individual profile zones can be added to or removed from PxProfileZoneManager.

PxProfileZoneManager instance is instantiated with the following code:

gProfileZoneManager = &PxProfileZoneManager::createProfileZoneManager(gFoundation);

Further key functions are

  • addProfileZone - adds a profile zone to the manager.
  • addProfileZoneHandler - adds a PxProfileZoneHandler to provide notifications about addProfileZone/removeProfileZone
  • removeProfileZoneHandler - removes a PxProfileZoneHandler.
  • removeProfileZone - removes a profile zone from the manager.
  • createProfileZone - creates a new profile zone and adds it to the manager.
  • release - destroys the profile zone manager.


PxProfileZone serves as an island of profile events. When flushProfileEvents is called, the flushed events buffer can be captured by all PxProfileZoneClient instances that have been added to the PxProfileZone. Example code is provided in Section PxProfileZoneClient and PxProfileEventHandler, while instantiation of a PxProfileZone is detailed in section Adding Custom Profile Zones.

Further key functions are

  • startEvent - starts the event profiling.
  • stopEvent - stops the event profiling.
  • addClient - adds PxProfileZoneClient.
  • removeClient - removes PxProfileZoneClient.
  • flushProfileEvents - flushes the profile events for PxProfileZoneClients.
  • release - destroys the profile zone.


The shutdown process follows the pattern typical of the PhysX SDK:


If a PxProfileZone has been instantiated outside the PhysX SDK then it must also be released:


Extracting PhysX SDK Event Data


The principal classes involved are PxDefaultBufferedProfiler and PxBufferedProfilerCallback. The event buffer, described in Section Basic Concepts, is flushed with the function PxDefaultBufferedProfiler::flushEvents. After calling this function the contents of the event buffer are sent (one event at a time) to the callback so that they may be recorded for later use. These classes shall be discussed in more detail in the following Sections.


Instances of PxDefaultBufferedProfiler are created by calling the function PxDefaultBufferedProfilerCreate. The specific profile zones that will be managed by the instantiated PxDefaultBufferedProfiler are governed by a string detailing the zone names.

Further key functions are

  • flushEvents - flushes all event buffers that were specified in PxDefaultBufferedProfilerCreate.
  • addBufferedProfilerCallback - adds a PxBufferedProfilerCallback instance, which receives the events after calling flushEvents.
  • removeBufferedProfilerCallback - removes a PxBufferedProfilerCallback instance.
  • release - releases the default buffered profiler.

Instances of PxDefaultBufferedProfiler must be created before the PxPhysics instance because the function PxCreatePhysics takes a reference to a PxFoundation as function argument. The extensions class PxDefaultBufferedProfiler constructs and owns the required PxProfileZoneManager instance. Example code is as follows:

// PxProfileZoneManager is instantiated before PxPhysics to ensure that a PxProfileZoneManager
// instance can be passed to PxCreatePhysics as a function argument.
gDefaultBufferProfiler = PxDefaultBufferedProfilerCreate(*gFoundation, "PhysXSDK ApexSDK");

gPhysics = PxCreatePhysics(PX_PHYSICS_VERSION, *gFoundation, PxTolerancesScale(), true,


The PxBufferedProfilerCallback class manages the reporting and recording of profile events after flushing the event buffer. When used in conjunction with PxDefaultBufferedProfiler the events in all profile zones being managed by the PxDefaultBufferedProfiler instance are sent to the callback. The function PxBufferedProfilerCallback::onEvent receives each event in sequence after the buffers have been flushed.

Events are sent to the callback using the PxBufferedProfilerEvent struct. This struct has several member variables:

  • startTimeNs - the event start time in nanoseconds.
  • stopTimeNs - the event end time in nanoseconds.
  • name - the event name.
  • profileZoneName - the name of the profile zone in which the event was generated.
  • contextId - the event contextId.
  • threadId - the thread in which the event was executed.
  • id - the event ID.
  • threadPriority - the priority of the thread in which the event was executed.
  • cpuId - the CPU on which the event was executed.

An example implementation is as follows:

// This is the main class that handles events and collects them for later printing
class SnippetBufferedProfilerCallback: public PxBufferedProfilerCallback
    // if the event buffer is flushed, each event is send in this callback
    virtual void onEvent(const PxBufferedProfilerEvent& event)
}   snippetBufferedProfilerCallback;

// we add our callback to receive events after the event buffer has been flushed.

For more implementation details please see the PxDefaultBufferedProfiler extension class and SnippetProfileZone.

Adding Custom Profile Zones


The key classes involved are PxProfileZoneManager, PxProfileZone and PxProfileNameProvider. For each PxProfileZone a PxProfileNameProvider instance is used to describe the mapping between profile event integer IDs and strings that are used for PVD visualization.

Custom profile events can be described with one or more PxProfileZone instances. Adding these PxProfileZone instances to the singleton PxProfileZoneManager instance (that is passed to PxCreatePhysics) allows custom events to be profiled in addition to PhysX profile events.

PxProfileNameProvider And Customization of PxProfileZone

The PxProfileNameProvider class describes the mapping between the integer ID of each custom profile event and a corresponding string used for visualization in PVD.

For example, three unique custom events with mapped strings can be added to the custom profile zone as follows:

// profile IDs used for identification within a profileZone
enum E_ProfileIds
    E_PROFILE_ID_1 = 1,

// profile events definitions
static PxProfileEventName gEventNames[] = {
    PxProfileEventName( "Profile_Id1", PxProfileEventId( E_PROFILE_ID_1 ) ),
    PxProfileEventName( "Profile_Id2", PxProfileEventId( E_PROFILE_ID_2 ) ),
    PxProfileEventName( "Profile_Id3", PxProfileEventId( E_PROFILE_ID_3 ) )

This mapping is passed to the PxProfileZone instance by first implementing a sub-class of PxProfileNameProvider and then passing an instance of the sub-class to PxProfileZone::createProfileZone. The following code creates an instance of a sub-class of PxProfileNameProvider:

struct ExampleProfileEventNameProvider : public physx::PxProfileNameProvider
    virtual physx::PxProfileNames getProfileNames() const
        return PxProfileNames(3,gEventNames);
ExampleProfileEventNameProvider    gExampleProfileZoneNameProvider;

The last step is to pass the mapping as a function argument to PxProfileZone::createProfileZone:

gProfileZone = &physx::PxProfileZone::createProfileZone(gFoundation,
    "ExampleProfileZone", gExampleProfileZoneNameProvider);

PxProfileZone is instantiated and added to the PxProfileZoneManager instance with the following code:

void createProfilerZone()


Each event in a profile zone can be profiled with the startEvent and stopEvent functions:

void updateProfileZones()
    // start profile zone 1
    gProfileZone->startEvent( E_PROFILE_ID_1,0);

    // start and end profile zone 2
        gProfileZone->startEvent( E_PROFILE_ID_2,0);
        gProfileZone->stopEvent( E_PROFILE_ID_2,0);

    // start and end profile zone 3
        gProfileZone->startEvent( E_PROFILE_ID_3,0);
        gProfileZone->stopEvent( E_PROFILE_ID_3,0);

    // end profile zone 1
    gProfileZone->stopEvent( E_PROFILE_ID_1,0);


Extracting PhysX SDK Event Data Using The PxProfileZoneManager Interface


The principal classes involved are PxProfileZoneManager, PxProfileZone and the event buffer described in Section Basic Concepts.

In order to flush the buffer of a profile zone, a reference to a PxProfileZone instance must first be retrieved. Profile zones internal to the PhysX SDK may be retrieved by implementing a sub-class of PxProfileZoneHandler and adding it to PxProfileZoneManager. The implemented functions PxProfileZoneHandler::onZoneAdded and PxProfileZoneHandler::onZoneRemoved receive references to affected profile zones.


PxProfileZoneHandler handles addition/removal of a PxProfileZone to/from PxProfileZoneManager. More specifically, it receives references to added/removed PxProfileZone instances. This is particularly useful for gaining access to profile event data that is internal to the PhysX SDK. The following code illustrates how this might be used in practice:

// our zone handler. This is used to watch for the zone we're interested in, and then hook
// our client into it.
class ExampleProfileZoneHandler: public PxProfileZoneHandler

    // check for the PhysXSDK profile zone
    virtual void onZoneAdded( PxProfileZone& inSDK )
        if(strstr(inSDK.getName(),"PhysXSDK") != 0)
            gPhysXProfileZone = &inSDK;

    virtual void onZoneRemoved( PxProfileZone&  )    {}

}   exampleProfileZoneHandler;

// first create the PxProfileZoneManager
gProfileZoneManager = &PxProfileZoneManager::createProfileZoneManager(gFoundation);

// when PhysX starts up, it will add a profile zone to the manager. We register the
// handler before creating PxPhysics, so that it receives the zone creation event.
// When we receive the event, we attach our client to the zone.

PxProfileZoneClient and PxProfileEventHandler

The class PxProfileZoneClient captures profile event data when the event buffer of a PxProfileZone instance is flushed using the function PxProfileZone::flushProfileEvents:

// our profile zone client. This forwards events to our handler object.
class ExampleProfileZoneClient : public PxProfileZoneClient
    virtual void handleEventAdded( const PxProfileEventName& ) {}
    virtual void handleClientRemoved() {}

    virtual void handleBufferFlush( const PxU8* inData, PxU32 inLength )
        PxProfileEventHandler::parseEventBuffer(inData, inLength, exampleProfileEventHandler,

}   exampleProfileZoneClient;

Registering the client with the profile zone can be achieved automatically by implementing the function PxProfileZoneHandler::onZoneAdded, as illustrated in Section PxProfileZoneHandler.

In ExampleProfileZone, the buffer is flushed immediately after the simulate step has been completed:

// in the update loop

// flush the profile zone events so we can parse them and get the recorded data


A complete set of PhysX SDK event data is guaranteed if the event buffer is flushed after PxScene::fetchResults has been called.

The PxProfileEventHandler class parses the flushed event buffer. Please note that events are sent per thread and that cross-thread events have a specific identifier PxProfileEventSender::CrossThreadId. An example of how to parse the events per thread is as follows:

// This is the main class that handles stop and start events and collects them for later printing
class ExampleProfileEventHandler: public PxProfileEventHandler

    static const PxU32     COLLECTION_SIZE = 1024;
    static const PxU32     NUM_COLLECTIONS = 16;

    // help structure to hold the event data. Times are in profiler ticks that are converted when
    // we print.
    struct ProfileEvent
        PxU16 id;
        PxU64 startTime;
        PxU64 stopTime;

        static const PxU64 INVALID_TIME = PxU64(-1);

    struct EventCollection
        PxU32              threadId;
        ProfileEvent       events[COLLECTION_SIZE];
        PxU32              numEvents;


    virtual void onStartEvent( const PxProfileEventId& inId, PxU32 threadId, PxU64 contextId,
        PxU8 cpuId, PxU8 threadPriority, PxU64 timestamp )

        EventCollection* threadCollection = findCollection(threadId);

        // add a new collection for this thread ID if it's not already there
            threadCollection = &mThreadCollections[mNumThreads++];
            threadCollection->threadId = threadId;
            PX_ASSERT(mNumThreads < NUM_COLLECTIONS);

        // add the event record
        ProfileEvent ev = { inId, timestamp, ProfileEvent::INVALID_TIME };
        threadCollection->events[threadCollection->numEvents++] = ev;

        PX_ASSERT(threadCollection->numEvents < COLLECTION_SIZE);

    virtual void onStopEvent( const PxProfileEventId& inId, PxU32 threadId, PxU64 contextId,
        PxU8 cpuId, PxU8 threadPriority, PxU64 timestamp )

        EventCollection* threadCollection = findCollection(threadId);
        PX_ASSERT(threadCollection != NULL);

        // an event (e.g. narrow phase batch) can occur several times per thread per frame, so
        // we take the earliest event with a matching ID that does not yet have a stop time
        for (PxU32 i = 0; i < threadCollection->numEvents; i++)
            ProfileEvent& ev = threadCollection->events[i];
            if( == inId.mEventId && ev.stopTime == ProfileEvent::INVALID_TIME)
                PX_ASSERT(timestamp > ev.startTime);
                ev.stopTime = timestamp;

    virtual void onEventValue( const PxProfileEventId& , PxU32 , PxU64 , PxI64  ) {}
    virtual void onCUDAProfileBuffer( PxU64 , PxF32 , const PxU8* , PxU32 , PxU32  ) {}

    void clear()
        mNumThreads = 0;
        mCrossThreadCollection.numEvents = 0;
        for (PxU32 i = 0; i < NUM_COLLECTIONS; i++)
            mThreadCollections[i].numEvents = 0;

    // lets print the stored events on screen
    void printEvents()
        printf("-------------------------- frame start -------------------------------- \n");

        printf("---------------------- Cross-thread events ---------------------------- \n");

        for (PxU32 j = 0; j < mNumThreads; j++)
            printf("\n---------------------- Thread ID %d events -------------------------- \n",

        printf("--------------------------- frame end --------------------------------- \n");

    EventCollection* findCollection(PxU32 threadId)
        if(threadId == PxProfileEventSender::CrossThreadId)
            return &mCrossThreadCollection;

        for (PxU32 i = 0; i < mNumThreads; i++)
            if(mThreadCollections[i].threadId == threadId)
                return &mThreadCollections[i];
        return NULL;

    void printCollection(const EventCollection &collection)
        for (PxU32 i = 0; i < collection.numEvents; i++)
            const ProfileEvent& ev =[i];
            const char* name = findEventName(;
            PxU64 duration = shdfnd::Time::getBootCounterFrequency().toTensOfNanos
                ( ev.stopTime - ev.startTime );
            float timeInMs = duration/100000.0f;
            printf("%-40s: %5.5f ms\n", name, timeInMs);

    const char* findEventName(PxU16 eventId)
        const PxProfileNames& names = gPhysXProfileZone->getProfileNames();
        for (PxU32 i = 0; i < names.mEventCount; i++)
            if(names.mEvents[i].mEventId.mEventId == eventId)
                return names.mEvents[i].mName;
        return "<unknown event>";

    EventCollection        mCrossThreadCollection;
    EventCollection        mThreadCollections[NUM_COLLECTIONS];
    PxU32                  mNumThreads;

}   exampleProfileEventHandler;