FSteamVRInputDevice::GetControllerOrientationAndPosition doesn't take into account XRSystem's BaseOrientation/BasePosition

[brendanwalker]

Apologies if I should have posted about this in the Discord channel first. Since this is a bit long winded I figured posting an issue made more sense:

If you use the XRSystem's ResetOrientationAndPosition call the BaseOrientation and BasePosition state are set. This call is used in "Moss" every time we transition to a new room and want to recenter on the room's camera. The FSteamVRHMD::PoseToOrientationAndPosition function is used to apply the inverse of the BaseOrientation and BasePosition to the controller pose.

I was expecting to see the same application here: https://github.com/ValveSoftware/steamvr_unreal_plugin/blob/4.21/SteamVRInput/Source/SteamVRInputDevice/Private/SteamVRInputDevice.cpp#L664-L669

I was able to work around this by adding the following state to FSteamVRInputDevice:

    // @POLYARC BEGIN
    /** Base Orientation defined by the XRTrackingSystem */
    FQuat CachedBaseOrientation;

    /** Base Position defined by the XRTrackingSystem */
    FVector CachedBasePosition;
    // @POLYARC END

Then caching those values in Tick:

void FSteamVRInputDevice::Tick(float DeltaTime)
{
    // @POLYARC BEGIN
    if (GEngine->XRSystem.IsValid())
    {
        CachedBaseOrientation = GEngine->XRSystem->GetBaseOrientation();
        CachedBasePosition = GEngine->XRSystem->GetBasePosition();
    }
    else
    {
        CachedBaseOrientation = FQuat::Identity;
        CachedBasePosition = FVector::ZeroVector;
    }
    // @POLYARC END
}

And then finally using those values in FSteamVRInputDevice::GetControllerOrientationAndPosition():

            // @POLYARC BEGIN
            //FVector Position = ((FVector(-Pose.M[3][2], Pose.M[3][0], Pose.M[3][1])) * GWorld->GetWorldSettings()->WorldToMeters);
            //OutPosition = Position;
            FVector Position = ((FVector(-Pose.M[3][2], Pose.M[3][0], Pose.M[3][1])) * GWorld->GetWorldSettings()->WorldToMeters - CachedBasePosition);
            OutPosition = CachedBaseOrientation.Inverse().RotateVector(Position);

            //OutOrientation.Normalize();
            //OutOrientation = OrientationQuat.Rotator();
            OrientationQuat = CachedBaseOrientation.Inverse() * OrientationQuat;
            OrientationQuat.Normalize();
            OutOrientation = OrientationQuat.Rotator();
            // @POLYARC END

If I'm not mistaken, we need to cache the values in Tick since GetControllerOrientationAndPosition() can be called in the render thread as part of the MotionControllers LateUpdate.

[1runeberg]

Thanks @brendanwalker, have reviewed, and this was overlooked during the re-implementation of the Motion Controller features - are you happy for me to integrate these to the code base similar to a Pull Request?

[brendanwalker]

Yeah totally happy! Thanks for taking a look.

[1runeberg]

Thanks Brendan! I've published develop-4.21 with your revisions included, comment link to this GitHub issue at Tick().

Can you check from your end please before I start propagating to other branches (min ver for this is 4.18 as far as I can tell)

[1runeberg]

@brendanwalker - quick nudge :) If you can do a finally verification please on your end before I propagate PR to main branches.

Cheers

[1runeberg]

Added in internal branches. Will be in 0.6 release.