Typing 90 degrees on the pitch axis showed 89.98. The stored quat is
exact (matrices differ by 0.0) -- the noise is display-side: quat's
sin(90) components square to 0.99999994 in float, and asin() diverges
at |sin|->1, amplifying 6e-8 into 0.02 degrees. Yaw/roll use atan2 and
were always exact, matching the user's report being X-axis only.
Two fixes, both aligned with how UE gets away with it (internally UE
is quat + equally pathological, its Details panel just shows one
decimal):
- GetRotation gimbal-lock threshold 1.0 -> 1-1e-6: pitch near +-90
now takes the composite-angle atan2 branch (ratio-stable) instead
of asin, so typing 90.0 reads back exactly 90.0. Probed: X=90 and
X=-90 now round-trip to 0 error; generic poses stay ~1e-6 deg.
- Rotation row shows one decimal ("%.1f", UE Details default), masking
the residual asin noise for angles near (not at) the pole; Ctrl+Click
input stays full precision. Negative zero from atan2 cleaned up.
Remaining asin noise for e.g. 89.9 (~9e-4 deg) is below the 1-decimal
display and unreachable in practice.
atdunbg
4fc48c21ac