From 948c4b0aa5404f3b4ea6b2bc32c85c4e6a02ceb6 Mon Sep 17 00:00:00 2001 From: Hakan Date: Sat, 23 May 2026 10:27:27 +0300 Subject: [PATCH] docs(perf): drop wire optimization plan now that all 4 steps shipped mapped_at_creation, rayon parallel emit, instanced rendering, and Unorm8x4 color packing all landed. Per-segment upload dropped from 576 B to 76 B (~7.6x). No follow-ups left. Co-Authored-By: Claude Opus 4.7 --- WIRE_OPTIMIZATION_PLAN.md | 80 --------------------------------------- 1 file changed, 80 deletions(-) delete mode 100644 WIRE_OPTIMIZATION_PLAN.md diff --git a/WIRE_OPTIMIZATION_PLAN.md b/WIRE_OPTIMIZATION_PLAN.md deleted file mode 100644 index aa331d413..000000000 --- a/WIRE_OPTIMIZATION_PLAN.md +++ /dev/null @@ -1,80 +0,0 @@ -# Wire Pipeline — Cold-Open Optimization Plan - -Goal: reduce first-file-open latency (tessellate → upload → GPU buffer -creation) for wire entities. Steady-state draw cost is already cheap; the -bottleneck on cold open is **upload volume** and **vertex emission**. - -## Baseline - -Each wire segment currently produces **6 vertices × 96 B = 576 B**. The same -`pos_a / pos_b / color / half_width / pattern_length / pat0 / pat1` values -are duplicated across all 6 corners of the quad. For a drawing with 1 M -segments this is **~576 MB** of CPU-side `Vec` plus the same -amount uploaded over PCIe. - -Build path: `WireGpu::from_batch` (single-threaded loop) → `Vec` -→ `create_buffer_init` (one alloc + one memcpy into a staging buffer the -driver then DMAs to VRAM). - -## Step 1 — `mapped_at_creation` upload - -Replace `create_buffer_init(contents)` with `create_buffer(mapped: true)` + -write the vertex stream directly into the mapped slice. Skips the -intermediate `Vec` → staging-buffer memcpy. - -- **Files**: `src/scene/pipeline/wire_gpu.rs` -- **Risk**: low (size known ahead of time; no semantic change). -- **Expected win**: 1 alloc + 1 memcpy per buffer dropped. Modest but free. - -## Step 2 — Rayon parallel vertex emission - -`from_batch` walks wires serially. Each wire's vertex generation is -independent (no shared state, no order dependency — wires are already -keyed by style upstream in `block_cache`). Use `rayon::par_iter().flat_map` -to emit per-wire vertex slices in parallel, then concatenate. - -- **Files**: `src/scene/pipeline/wire_gpu.rs` -- **Risk**: low. Output ordering does not matter for correctness. -- **Expected win**: N-core speedup on multi-wire drawings; meaningful on - files with many short wires (typical CAD geometry). - -## Step 3 — Instanced rendering (the big win) - -Replace 6-vertex quad expansion with **1 instance per segment** + 4-vertex -unit quad shared across all instances. Per-instance struct (~88 B) holds: -`pos_a, pos_b, color, distance_a, distance_b, half_width, pattern_length, -pat0, pat1`. `which_end` and `side` are derived from `@builtin(vertex_index)` -inside the vertex shader. - -- **Files**: `src/scene/pipeline/wire_gpu.rs`, `src/shaders/wire.wgsl`, - `src/scene/pipeline/mod.rs` (pipeline `VertexBufferLayout`). -- **Risk**: medium. Two vertex buffers (per-vertex + per-instance), shader - derives `which_end` / `side` from `vertex_index`. `WireGpu::from_batch` - emits 1 instance per segment instead of 6 verts. -- **Expected win**: **~6.5× less GPU memory & upload bandwidth per - segment** (576 B → 88 B). Biggest cold-open lever. - -## Step 4 — Tighter per-instance packing - -After Step 3 the instance struct is the new hot path. Pack: - -- `color: [f32; 4]` → `[u8; 4]` (`Unorm8x4`): 16 B → 4 B, no visible - quality loss at 8-bit display. -- `which_end / side` already eliminated by Step 3. -- `pat0 / pat1` stay (encoder relies on up to 8 dash elements). - -Net: ~88 B → ~76 B per instance. ~15 % further reduction on top of Step 3. - -- **Files**: `src/scene/pipeline/wire_gpu.rs`, `src/shaders/wire.wgsl`. -- **Risk**: low (vertex-attribute format change only). -- **Expected win**: ~15 % less upload after Step 3. - -## Ordering rationale - -1-2 first — independent, low risk, immediate wins. -3 next — restructures the pipeline; depends on no prior changes but is the -single biggest lever. -4 last — only pays off after Step 3 turns the per-instance struct into the -hot path. - -Each step ends with a `cargo check` (warnings-free) and a commit.