I engineered a portable, half-dome, USB-triggered, bracketed HDRI rig to record time-scrubbable lighting on location (golden hour → dusk). The goal: let artists pick the exact minute of sky/sun for virtual production instead of swapping static HDRIs.
Tech snapshot: 5 fisheye cameras (~15% overlap), 10-shot HDR brackets per interval, scripted PTGui auto-align (~15 min per set), Nuke cleanup → 8–32k EXR lat/long. v1 uses software simultaneity (stills). The v2 roadmap adds genlock + shared timecode and global-shutter sensors for true video-rate capture.
Overview
In virtual production we often swap static HDRIs. I wanted a movable, real-location rig that could sit through golden hour and record continuous HDRI sets over time, so you can scrub to the perfect minute of sky and sun.
Hardware & Layout
• Form factor: Half-dome, ~180° FOV
• Array: 5× fisheye cameras (~15 mm), ~10–15% overlap between neighbors
• Mounting: Indexed positions on a ring; leveled and repeatable
• Connectivity: Each camera → powered USB hub → laptop
• Triggering: Software/USB simultaneous shutter command across all cameras (v1)
Capture Protocol
• Bracketing: 10 exposures per camera to cover full dynamic range
• Session length: Multi-hour intervals (sunrise/sunset windows)
• Matching: Identical WB/ISO/shutter progression across the array; settings logged
• Overlap: 10–15% neighbor overlap for robust stitching with minimal redundancy
Processing Pipeline
1) PTGui (templated alignment): Saved control-point templates and batch scripts enable auto-align per bracket set (~15 minutes) thanks to consistent geometry/overlap.
2) Nuke (assembly/cleanup): Exposure fusion to 32-bit EXR, seam blending, ghost removal (foliage/people), horizon leveling.
3) Output: 8–32k lat/long EXR sequences at chosen intervals, plus preview JPGs/MP4s.
Results
• Time-scrubbable HDRI sequences from one vantage point—great for dialing precise golden-hour or cloud-break looks without swapping maps.
• Reliable still capture via USB simultaneity for brackets; portable and deployable on short notice.
Challenges & Lessons
• Temporal jitter: Software triggers are “now(ish).” Fine for still brackets; not a substitute for genlock if you need multi-cam video-rate capture.
• Scene motion: Clouds/trees/traffic can introduce stitching drift—mitigated with shorter intervals, robust control points, and Nuke cleanup.
• Power/thermals: Multi-hour operation needed active power management and shade for camera bodies.
v2 Roadmap (what I’d build next)
• Genlocked sensors + shared timecode (phase-locked exposure boundaries across cameras)
• Global-shutter industrial cameras with tri-level sync to avoid rolling artifacts
• On-rig metadata logger (CSV/JSON): lens, WB/ISO/shutter per bracket; GPS; sun az/el; conditions
• Automated ingest/QC: checksums, proxy generation, bracket validation, quick sky-luminance graphs
Related Ambition — Head Capture Rig
In parallel, I’m planning a cross-polarized head-capture array for hero neutral assets (true albedo/spec separation) with stabilized three-point head/neck support. The intent is to pair material truth (cross-pol stills) with motion truth (multi-view video) in a single pipeline.
Credits & Tools
• Capture/Engineering: Tripp Topping
• Software: PTGui (templated), Nuke (assembly/cleanup)
• Deliverables: 32-bit EXR (lat/long), preview JPG/MP4 time-lapses
