Ludovic Marie
73 lines
4.3 KiB
Markdown
73 lines
4.3 KiB
Markdown
# Matched graphics API comparison
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Three core-profile pairs compare OpenGL with Vulkan at the same stationary view.
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On this Linux software renderer, Vulkan produces only 1.22–1.74% more average FPS
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while using 11.23–12.95% more process CPU. Frame-time tails and sampled RSS are
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mixed, and integrated-server tick execution is slower. Playable backend defaults
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remain unchanged. These results do not predict physical M2 GPU performance.
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## Protocol
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Each fresh process uses the exact published 0.20.0 mod, identical core mods,
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private camera fixture, initial world copy and 3 GiB maximum / 512 MiB initial
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heap. Both APIs use 12 full-detail / 12 simulation chunks, 1280×800, FOV 70,
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uncapped FPS, no LOD/shaders, G1 and compact headers. Every original experimental
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controller is disabled. The private camera is fixed and world copies use Peaceful
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difficulty with noon/weather advancement rules fixed. Playable packs retain
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normal rules.
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Runs warm for 180 seconds, then record frames and ticks for 120 seconds. Each
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pair runs OpenGL first and Vulkan second. Actual devices report llvmpipe LLVM
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21.1.8, with Mesa 26.0.8 OpenGL 4.5 or Vulkan 1.4.335. The Vulkan preference is
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verified against the observed backend; a fallback would invalidate this series.
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The host is an i7-7500U with 2 physical cores / 4 logical processors and about
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30.2 GiB system RAM. Native GPU access is unavailable to this user.
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## Results
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| Pair | OpenGL FPS | Vulkan FPS | OpenGL CPU | Vulkan CPU | OpenGL peak RSS | Vulkan peak RSS | Tick mean, OpenGL → Vulkan |
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| --- | ---: | ---: | ---: | ---: | ---: | ---: | ---: |
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| 1 | 6.5786 | 6.6765 | 2.895 cores | 3.248 cores | 2,362.36 MiB | 2,337.00 MiB | 6.455 → 7.460 ms |
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| 2 | 6.5869 | 6.6671 | 2.918 cores | 3.246 cores | 2,471.90 MiB | 2,526.52 MiB | 6.845 → 7.602 ms |
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| 3 | 6.5632 | 6.6775 | 2.879 cores | 3.252 cores | 2,424.70 MiB | 2,459.63 MiB | 6.499 → 7.593 ms |
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Paired FPS changes are +1.49%, +1.22%, +1.74%, with a descriptive arithmetic
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mean of +1.48%. CPU changes are +12.18%, +11.23%, +12.95% (mean +12.12%).
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These three fixed-order pairs do not establish statistical significance.
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p95 frame intervals change −2.08%, +0.94%, −1.43%; slowest-1%-average FPS
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changes −2.19%, −7.63%, +5.49%. Peak sampled RSS changes −1.07%, +2.21%,
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+1.44%. GC accounting is mixed and is not a measured stop-the-world pause total.
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Tick execution means increase 11.06–16.84%, while observed invocation throughput
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remains near 20 TPS with normal sampled tick-manager state in all runs.
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Process CPU includes native rendering and the integrated server. Higher tick
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durations in a shared rendering process do not isolate a server algorithm change
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or establish dedicated-server capacity. Tick reports do not capture the client
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graphics API; their captured-settings match must be interpreted alongside each
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paired frame report's explicit backend/driver differences.
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## Validation and limits
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All six clients save and exit cleanly. Raw frame/tick CSV counts and mean durations
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match the JSONs, with zero exclusions/drops. Runtime and fixture hashes, mod
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identities, other captured settings, saved camera/position and clock/weather rules
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match. Frame comparisons retain only the deliberate backend/driver mismatches.
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Both first-pair warmed views were visually inspected before recording and showed
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the same forest/terrain. This is not an exhaustive pixel-equivalence test.
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All three actual frame/tick JSON+CSV pairs pass desktop/mobile viewer and chart
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checks; representative screenshots were inspected. The
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[selected observations](../benchmarks/graphics-api-2026-10-04/live-observations.json)
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retain all six runs, every paired metric, configuration, device identities and
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private capture/fixture hashes. Raw logs, CSVs, images and worlds remain private.
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One stationary view, a software renderer, fixed order and three pairs cannot
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establish movement/generation behavior, native GPU or Mac speedups, full visual
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equivalence or populated-server capacity. OS cache, JIT, entities and thermal
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effects can still vary. Sampled RSS covers the settled recording, can miss spikes
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and is not complete GPU/unified-memory accounting. Do not pool these API pairs
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with heap or vanilla/core experiments. See the [Mac procedure](mac-first-test.md)
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for physical-device comparisons and the [graphics probes](client-graphics-smoke.md)
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for separate hosted-Mac startup results.
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