spatial-rendering-and-performancelisted

# Spatial Rendering & Performance The discipline of holding the frame. In XR a dropped frame is discomfort, so the frame budget is the top constraint and everything else is spent against it. > **Engineering judgment.** Per-device ms budgets, draw-call ceilings, render-feature support, and thermal limits move with hardware and SDK versions — every number here is `[verify-at-use]`. No PII. ## Workflow 1. **Derive the per-eye budget.** Refresh rate fixes frame time (e.g., 72/90/120 Hz -> the matching ms). That is the hard ceiling. 2. **Profile on device to find the bound.** CPU-bound (draw calls, physics, scripting) vs GPU-bound (fill rate, overdraw, shader cost) vs thermal-throttled demand opposite fixes. Editor numbers are not device numbers. 3. **Cut in order.** Draw calls (batching/instancing, atlasing, single-pass stereo), then overdraw/transparency, then shader cost, then geometry/LOD. Highest leverage first. 4. **Spend headroom deliberately.** Foveated rendering (fixed or eye-tracked) buys GPU headroom; reprojection (ASW/spacewarp-style) covers occasional misses. Constant reprojection means you are over budget — fix the budget, don't lean on the net. 5. **Budget for thermal-sustained.** Test a sustained session and hold the budget at the throttled clock, not the 30-second-demo peak. ## Metrics table | Metric | Target/read | Flag | |---|---|---| | Per-eye frame time vs budget (ms) | At or under the device's refresh-derived budget | `[verify-at-use]` per device | | Re