81 lines
3 KiB
Markdown
81 lines
3 KiB
Markdown
# lofivor - build roadmap
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survivor-like optimized for weak hardware. finding the performance ceiling first, then building the game.
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## phase 1: sandbox stress test
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- [x] create sandbox.zig (separate from existing game code)
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- [x] entity struct (x, y, vx, vy, color)
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- [x] flat array storage for entities
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- [x] spawn entities at random screen edges
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- [x] update loop: move toward center, respawn on arrival
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- [x] render: filled circles (4px radius, cyan)
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- [x] metrics overlay (entity count, frame time, update time, render time)
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- [x] controls: +/- 100, shift +/- 1000, space pause, r reset
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## phase 2: find the ceiling
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- [x] test on i5-6500T / HD 530 @ 1280x1024
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- [x] record entity count where 60fps breaks
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- [x] identify bottleneck (CPU update vs GPU render)
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- [x] document findings
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findings (AMD Radeon test):
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- 60fps breaks at ~5000 entities
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- render-bound: update stays <1ms even at 30k entities, render time dominates
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- individual drawCircle calls are the bottleneck
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## phase 3: optimization experiments
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based on phase 2 results:
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- [x] batch rendering via texture blitting (10x improvement)
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- [x] rlgl quad batching (2x improvement on top)
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- [x] ~~if cpu-bound: SIMD, struct-of-arrays, multithreading~~ (not needed)
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- [x] re-test after each change
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findings:
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- texture blitting: pre-render circle to texture, drawTexture() per entity
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- rlgl batching: submit vertices directly via rl.gl, bypass drawTexture overhead
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- baseline: 60fps @ ~5k entities
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- after texture blitting: 60fps @ ~50k entities
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- after rlgl batching: 60fps @ ~100k entities
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- total: ~20x improvement from baseline
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- see journal.txt for detailed benchmarks
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further options (if needed):
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- increase raylib batch buffer (currently 8192 vertices = 2048 quads per flush)
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- GPU instancing (single draw call for all entities)
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- or just move on - 100k @ 60fps is a solid ceiling
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## phase 4: spatial partitioning
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- [ ] uniform grid collision
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- [ ] quadtree comparison
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- [ ] measure ceiling with n² collision checks enabled
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## phase 5: rendering experiments
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- [x] increase raylib batch buffer (currently 8192 vertices = 2048 quads)
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- [x] GPU instancing (single draw call for all entities)
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- [x] SSBO instance data (12 bytes vs 64-byte matrices)
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- [ ] compute shader entity updates (if raylib supports)
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- [ ] compare OpenGL vs Vulkan backend
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findings (i5-6500T / HD 530):
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- batch buffer increase: ~140k @ 60fps (was ~100k)
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- GPU instancing: ~150k @ 60fps - negligible gain over rlgl batching
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- instancing doesn't help on integrated graphics (shared RAM, no PCIe savings)
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- bottleneck is memory bandwidth, not draw call overhead
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- rlgl batching is already near-optimal for this hardware
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## future optimization concepts
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- [ ] SIMD entity updates (AVX2/SSE)
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- [ ] struct-of-arrays vs array-of-structs benchmark
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- [ ] multithreaded update loop (thread pool)
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- [ ] cache-friendly memory layouts
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- [ ] LOD rendering (skip distant entities or reduce detail)
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- [ ] frustum culling (only render visible)
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- [ ] temporal techniques (update subset per frame)
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- [ ] fixed-point vs floating-point math
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