Accurately trigger the preview slider update based on FPS

[RongLiu-Leo]

Problem

Slider → Preview Camera Updates
Whenever the slider’s value changes, it recomputes and updates the preview camera’s position.

Two Tasks

1. Play Mode
   • Animates a green camera along the trajectory.
   • After receiving the camera updates, uses time.sleep(1/fps) between updates to pace the animation.
2. Preview Mode
   • Sets the user’s camera to the preview pose and renders frames.
   • No Sleep, so updates fire as fast as possible, outpacing the renderer and causing visible jumps.

Windows Limitation

• time.sleep() on Windows cannot reliably pause for very precise intervals, especially at high frame rates.

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This PR

Accurate Timing with time.perf_counter()

• Tracks elapsed time since the last update.
• Ensures at least 1/fps seconds have passed before applying the next slider change.
• No need for all downstream sleep() calls in both modes.

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Future Considerations

Sustaining High FPS

• If the user requests a high frame rate, can the system truly maintain 1/fps-second response times under load? I think this is the bottleneck for current FPS-timer logic.This PR performs better but still jumps given a high FPS.

Send–Ack–Send Handshake

• A more robust approach would wait for the renderer’s acknowledgement before scheduling the next update.
• Pros: Guarantees no dropped or out-of-order frames.
• Cons: May introduce back-pressure and reduce overall throughput; requires performance testing.