Why is the driver pose different from the application pose?

[2621690255]

For example, I have a position(1.0f, 2.0f, 3.0f) and a rotation (0.948324f, 0.317305f, 0.0f, 0.0f), Rotate around the x-axis by 30 degrees.

vr::DriverPose_t outPose;
outPose.vecPosition[0] = 1.0;
outPose.vecPosition[1] = 2.0;
outPose.vecPosition[2] = 3.0;
outPose.qRotation = { 0.948324f, 0.317305f, 0.0f, 0.0f };

outPose.qWorldFromDriverRotation = { 1.0f, 0.0f, 0.0f, 0.0f };
outPose.qDriverFromHeadRotation = { 1.0f, 0.0f, 0.0f, 0.0f };
outPose.poseIsValid = true;
outPose.deviceIsConnected = true;
outPose.result = vr::TrackingResult_Running_OK;
outPose.shouldApplyHeadModel = true;
// update pose to steamvr

In unity, I will get this result (1.0f, 2.024904f, 3.087058f) and a rotation (0.948324f, 0.317305f, 0.0f, 0.0f).

[fww0071215]

Perhaps you should take a look at the Unity-related code. In UE4, UE4 retrieves the position from SteamVR and performs some transformations. Additionally, the repositioning is also handled by UE4, which is why the final position displayed differs from the position reported by SteamVR.