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VP Zoom Data Sent to Unreal Before Physical Motor Arrives — Tracking Lag (Open)

Summary

In virtual production LED volume setups, Flair sends zoom data to Unreal Engine (for frustum rendering) based on the commanded zoom position — not the actual position that the physical zoom motor has reached. Since the physical zoom motor has latency (servo response time), the rendered frustum in Unreal updates faster than the physical lens changes. This means the LED wall shows a slightly different focal length than the camera is physically seeing, causing a momentary mismatch during zoom moves. The mismatch is most visible on active zoom shots and is partially visible as fringing or focus plane drift at the edges of the LED wall. No definitive fix has been confirmed in the community.

Symptoms

  • During zoom moves on an LED volume, the LED wall appears to "jump" ahead of the physical zoom.
  • Edge fringing or focus plane mismatch visible on LED wall during zoom transitions.
  • Static shots (no zoom) are correct; issue only appears when zooming.
  • Zoom data arrives in Unreal correctly but is ahead of what the physical lens is seeing.

Community Guidance

[OPEN — UNRESOLVED] Physical Motor Lag vs. Data Transmission Timing

Community — 2022

This is a fundamental timing issue: Flair sends the commanded zoom value to Unreal at the moment the command is issued, but the physical servo/motor takes time (typically 50–300ms depending on motor speed and gear ratio) to actually move the lens. The rendering engine updates immediately; the lens catches up later.

Partial workarounds (not confirmed solutions):

  1. Slow down zoom moves — at very slow zoom speeds, the motor lag is negligible relative to the move duration.
  2. Apply a Blueprint delay to the Unreal zoom data — delay the zoom value by approximately the motor's response time. See VP Tracking Delay Compensation for the delay node approach.
  3. Use a high-speed zoom motor with low gear ratio to reduce motor lag to the minimum.
  4. Avoid active zoom shots during LED volume photography where the mismatch would be visible.

Report to MRMC if this causes issues: support@mrmoco.com — a future Flair update could potentially transmit actual motor encoder position rather than commanded position.

confidence_score: 0.83