Fix XrNavigation NaN rig corruption on gamepads without thumbstick axes#8850
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XrNavigation reads thumbstick input from gamepad.axes[2]/[3] (the WebXR xr-standard mapping). Apple Vision Pro hand-tracking input sources expose a gamepad with an empty axes array, so those reads return undefined and -undefined is NaN. The smooth-turn guard 'Math.abs(turn) <= threshold' does not catch NaN (NaN comparisons are always false), so the NaN flowed into rotateLocal and corrupted the camera rig transform to NaN permanently. Splats still submitted but projected to NaN, leaving the scene blank in VR on AVP while head tracking worked. Controller headsets (Quest) report real axes and were unaffected. Skip input sources whose gamepad does not expose thumbstick axes (axes.length < 4) in handleSmoothLocomotion and handleSnapVertical.
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mvaligursky
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…es (#8850) XrNavigation reads thumbstick input from gamepad.axes[2]/[3] (the WebXR xr-standard mapping). Apple Vision Pro hand-tracking input sources expose a gamepad with an empty axes array, so those reads return undefined and -undefined is NaN. The smooth-turn guard 'Math.abs(turn) <= threshold' does not catch NaN (NaN comparisons are always false), so the NaN flowed into rotateLocal and corrupted the camera rig transform to NaN permanently. Splats still submitted but projected to NaN, leaving the scene blank in VR on AVP while head tracking worked. Controller headsets (Quest) report real axes and were unaffected. Skip input sources whose gamepad does not expose thumbstick axes (axes.length < 4) in handleSmoothLocomotion and handleSnapVertical. Co-authored-by: Martin Valigursky <mvaligursky@snapchat.com>
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Entering VR on Apple Vision Pro left the scene blank (only the camera clear color visible) while head tracking worked. The camera rig transform was being corrupted to NaN on the second XR frame.
Cause:
XrNavigation reads thumbstick input from
gamepad.axes[2]/[3](the WebXR xr-standard mapping). AVP hand-tracking input sources expose a gamepad with an empty axes array, so those reads returnundefinedand-undefinedisNaN.The visible corruption was specific to
turnMode: 'smooth'— its guardMath.abs(turn) <= thresholddoes not catch NaN (NaN comparisons are always false), so the NaN flowed intorotateLocaland corrupted the rig — and its child camera — to NaN permanently. Splats still submitted but projected to NaN, so nothing rasterized.This was not a problem in the general case: the snap-turn path (
Math.abs(rotate) > threshold) and smooth locomotion (length() > threshold) gate on conditions that are correctly false for NaN, so they were already inert with absent axes — they just never moved. Only the smooth-turn polarity let NaN through. Controller-based headsets (Quest) report realaxes[2] = 0and were unaffected regardless of turn mode.Changes:
axes.length < 4) inhandleSmoothLocomotion(covers locomotion and both turn modes) andhandleSnapVertical.On hand-tracking-only devices, thumbstick locomotion/turning is now cleanly inert (there is no thumbstick to drive it) rather than corrupting the rig. Devices with conformant xr-standard gamepads report 4 axes and are unchanged.