docs: iPhone Pro performance analysis — lag, input delay & overheating

[web3dev1337]

Summary

• Deep investigation into why high-end iPhones (Pro models: 120Hz ProMotion, 3x DPR) experience thermal throttling, multi-second input delay, and frame drops while lower-end iPhones run fine
• Identifies 13 contributing factors ranked by likelihood, impact, fix complexity, confidence, and risk
• Root cause: Pro iPhones do 4.5x more GPU work than base iPhones on the same quality preset (120Hz uncapped + 3x pixel ratio + full post-processing)

Top 5 Findings

#	Issue	Impact
1	No FPS cap on MEDIUM/HIGH — renders at full 120Hz	Critical
2	3x DPR unscaled — 2.25x more pixels than 2x devices	Critical
3	Outline shader: 128 texture samples/pixel saturates GPU bandwidth	Critical
4	All post-processing (outline+bloom+SMAA) enabled on mobile MEDIUM	High
5	Auto-quality ping-pong from thermal throttling oscillations	High

Additional Findings

• Mobile input hardcoded to 30Hz (4x mismatch with 120Hz render)
• CSS2DRenderer DOM thrashing 120x/sec
• Synchronous gunzipSync on main thread
• No WebTransport on iOS (Apple limitation)
• Aggressive chunk loading with no rate limiting

Deliverable

docs/performance/IPHONE_PRO_PERFORMANCE_ANALYSIS.md — full analysis with issue matrix, code locations, bandwidth math, and prioritized fix recommendations.

Test plan

• Review analysis against actual client source code paths cited
• Validate bandwidth math for outline shader on Pro iPhone specs
• Confirm fix priorities align with team capacity
• Use findings to create implementation tickets for fixes

🤖 Generated with Claude Code