fix: Fix per-physics-step tick jitter under sync_to_physics#626
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elementbound merged 5 commits intoJul 8, 2026
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Under netfox/time/sync_to_physics = true, the tick loop runs inside _physics_process, but it still decides how many ticks to run from netfox's own wall-clock scheduler rather than from the physics step it's running in. Because that wall clock drifts against Godot's physics accumulator, individual physics steps end up running 0 or 2 ticks instead of 1, several times per second. At the same time, when sync_to_physics is on, tick_factor is derived from Engine.get_physics_interpolation_fraction() — i.e. the physics-step timeline. So every 0/2-tick slip produces a from/to interpolation pair that disagrees with the fraction: TickInterpolator renders a backward snap followed by a double-speed catch-up. It reads as intermittent movement jitter. The severity is set by the phase between the two clocks, which is frozen at NetworkTime.start() — so the same project stutters on some launches and is smooth on others, and the state persists for the whole session.
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Under netfox/time/sync_to_physics = true, the tick loop runs inside _physics_process, but it still decides how many ticks to run from netfox's own wall-clock scheduler rather than from the physics step it's running in. Because that wall clock drifts against Godot's physics accumulator, individual physics steps end up running 0 or 2 ticks instead of 1, several times per second.
At the same time, when sync_to_physics is on, tick_factor is derived from Engine.get_physics_interpolation_fraction() — i.e. the physics-step timeline. So every 0/2-tick slip produces a from/to interpolation pair that disagrees with the fraction: TickInterpolator renders a backward snap followed by a double-speed catch-up. It reads as intermittent movement jitter.
The severity is set by the phase between the two clocks, which is frozen at NetworkTime.start() — so the same project stutters on some launches and is smooth on others, and the state persists for the whole session.