openvr_string
openvr_string extends the C++ OpenVR SDK by making it easy to convert OpenVR objects into strings. These strings are helpful for logging, tracing and debugging your VR applications.
Interfaces
- openvr_string.h defines the complete set of struct and enum to string conversion routines. This covers all openvr structs and enums.
- openvr_string_std.h provides a to_string() converter that works with all of the openvr structs and enums to make std::strings.
- openvr_string_qstring.h provides a to_qstring() converter that works with all of the openvr structs and enums to make Qt strings.
The to_string and to_qstring functions work by encoding into a buffer on the stack (falling back onto heap on failure).
Example 1: Controller States
Suppose you wanted to look at controller states with every frame.
for( vr::TrackedDeviceIndex_t unDevice = 0; unDevice < vr::k_unMaxTrackedDeviceCount; unDevice++ ) {
vr::VRControllerState_t state;
if( m_pHMD->GetControllerState( unDevice, &state ) )
dprintf("Polled Controller %d State:\n%s", unDevice, to_string(state).c_str());
}
Will give you output like the following:
Polled Controller 3 State:
unPacketNum: 1827
ulButtonPressed: k_EButton_Axis0 (100000000)
ulButtonTouched: k_EButton_Axis0 (100000000)
rAxis[0]: 0.065527 -0.724208
rAxis[1]: 0.000000 0.000000
rAxis[2]: 0.000000 0.000000
rAxis[3]: 0.000000 0.000000
rAxis[4]: 0.000000 0.000000
In this case I pressed down on the touchpad close to the centre of X (0.065527) and near the bottom of Y (-0.724208).
For a full example of this, build and enable the g_print_polled_controller_state of the following hellovr_opengl sample.
Example 2: Events
Suppose you want to log all events processed by the following function:
There are nearly 20 different event subtypes, each with their own parameters and enums. You could convert this by hand... or you could use the openvr_string std::string wrapper:
void CMainApplication::ProcessVREvent( const vr::VREvent_t & event )
{
dprintf("%s\n", to_string(event).c_str());
}
And that's all it takes to get:
eventType: VREvent_TrackedCamera_ResumeVideoStream (1503)
trackedDeviceIndex: 0
eventAgeSeconds: 1.601475
dataType: None (0)
eventType: VREvent_ChaperoneUniverseHasChanged (801)
trackedDeviceIndex: 0
eventAgeSeconds: 0.000315
dataType: Chaperone (11)
m_nPreviousUniverse: 0
m_nCurrentUniverse: 579ad90c
eventType: VREvent_ButtonTouch (202)
trackedDeviceIndex: 3
eventAgeSeconds: 0.463968
dataType: Controller (2)
eventDetails: k_EButton_Grip (2)
Example 3: Compositor Frame Timing
As another example, output the the Compositor frame timing like this:
timing.m_nSize = sizeof(timing);
vr::VRCompositor()->GetFrameTiming(&timing);
dprintf("Frame Timing\n%s\n", to_string(timing).c_str());
To get:
Frame Timing
m_nSize: 176
m_nFrameIndex: 31137
m_nNumFramePresents: 1
m_nNumDroppedFrames: 0
m_nReprojectionFlags: 0
m_flSystemTimeInSeconds: 353.053773
m_flPreSubmitGpuMs: 0.000000
m_flPostSubmitGpuMs: 0.000000
m_flTotalRenderGpuMs: 1.442112
m_flCompositorRenderGpuMs: 1.242112
m_flCompositorRenderCpuMs: 0.401727
m_flCompositorRenderIdleCpuMs: 7.827824
m_flClientFrameIntervalMs: 0.000000
m_flPresentCallCpuMs: 0.062197
m_flWaitForPresentCpuMs: 0.007211
m_flSubmitFrameMs: 0.000000
m_flWaitGetPosesCalledMs: 0.000000
m_flNewPosesReadyMs: -3.017913
m_flNewFrameReadyMs: 0.000000
m_flCompositorUpdateStartMs: -3.016410
m_flCompositorUpdateEndMs: -3.009500
m_flCompositorRenderStartMs: -3.008898
m_HmdPose:
mDeviceToAbsoluteTracking: -0.195222 -0.973346 -0.120360 -0.042309
0.654561 -0.037917 -0.755058 1.000905
0.730369 -0.226187 0.644516 0.292073
vVelocity: -0.001909 -0.001982 0.003239
vAngularVelocity: 0.040071 -0.028047 0.000863
eTrackingResult: TrackingResult_Running_OK (200)
bPoseIsValid: true
bDeviceIsConnected: true
Implementation
- At the lowest level, the openvr_strings uses snprintf functions to write into buffers provided by the caller. You can access these apis directly from the openvr_string.h header file.
- For enum conversions, Valve does provide some enum conversions for about 10 enums, in these cases their APIs are used. For the remainder custom generated enum code is included.
- The struct conversions are hand rolled and call down into the enum and snprintf encoders.
- to_string and to_qstring functions work by encode into a buffer on the stack before falling back onto heap.
There is no global state or heap allocated internally. This means it's thread-safe and lighter weight than solutions that alloc from the heap.
More Examples
The hellovr_opengl example and the tracked_camera_openvr_sample have been modified and included to show using the openvr_strings.
- hellovr_opengl now defines a set of global flags that turns on or off the level of logging desired for events, controller and render state. It uses the std::string to_string conversion routines.
- tracked_camera_openvr_sample has been modified to use the to_qstring conversion routines instead of the pre-existing Qt formatting for the frame header pose matrix, velocity and anggular velocities.