Avatar sinks below the floor on first load (desktop mode) when eye height is below 1.61 m

[minetake01]

Describe the bug?

On desktop mode, loading an avatar whose eye height is shorter than the 1.61 m fallback causes the avatar root to be placed below the floor on every frame until manual full-body calibration is performed. The feet visually sink into the floor up to roughly knee depth.

The issue persists after the T-pose phase ends and continues throughout normal play.

Steps to Reproduce

1. Launch BasisVR in desktop mode (no HMD connected).
2. Load any avatar whose eye height is below 1.61 m (e.g. a small/short humanoid avatar).
3. Observe the avatar immediately after loading — the feet sink into the floor.
4. Confirm the sinking persists in normal play (T-pose phase over, IK active).
5. Perform a full-body calibration (Settings → Calibration). Observe the avatar returns to the correct floor level.

The expected behavior

The avatar should stand with its feet on the floor immediately after loading, without requiring a manual full-body calibration.

Screenshots

Build Info

Version: 2.0.1
Unity: 6000.4.5f1
Platform: WindowsEditor
Mode: Desktop
Build GUID: 00000000000000000000000000000000

Log Files

N/A

Additional Context

PlayerEyeHeight defaults to 1.61 m (BasisHeightDriver.cs L29) and is only updated by CapturePlayerHeight(), which is called during full-body calibration. On desktop mode there is no HMD to measure the real player height, so the value stays at 1.61 m.

DeviceScale is then computed as (BasisHeightDriver.cs L287–L290):

float avatarScaledMetric = SelectedUnScaledAvatarHeight * AppliedUpScale;  // e.g. 1.12
float playerMetric       = AdditionalPlayerHeight + SelectedUnScaledPlayerHeight; // 0 + 1.61
DeviceScale = avatarScaledMetric / playerMetric;  // → 0.696

BasisDesktopEye uses DeviceScale to project the simulated head position (BasisDesktopEye.cs L314–L316):

ScaledDeviceCoord.position = OffsetCoords.position
    + (OffsetCoords.rotation * (UnscaledDeviceCoord.position * deviceScale));

Unlike VR, the desktop UnscaledDeviceCoord is already sourced from the avatar's T-pose bone positions, not a real-world HMD measurement. Multiplying by DeviceScale < 1 pushes the simulated head below its correct height:

ScaledDeviceCoord.y = 1.12 × 0.696 = 0.78 m

DriveTpose() then places the avatar root at headPosWS − TposeLocalScaled.head (BasisLocalPlayer.cs L534–L536):

avatarRoot.y = 0.78 − 1.12 = −0.34 m  (34 cm below the floor)

This is applied every frame while CurrentlyTposing == true, and the incorrect DeviceScale carries over into the IK phase after T-pose ends.

[Toys0125]

I see this issue with the froggy car as well, since the view point is now in the ground.