forked from 1b-agent/opencadstudio-upstream
Hakan SevenandClaude Sonnet 4.6
9c8c9a4060
Replace the O(objects) linear scan inside wires_for_block() with a sort_cache keyed by geometry_epoch. On a cache miss the index is built once by scanning all document objects; subsequent calls within the same epoch do an O(1) HashMap lookup (block_handle → entity→sort map). Co-Authored-By: Claude Sonnet 4.6 <[email protected]>
125 lines
5.1 KiB
Markdown
125 lines
5.1 KiB
Markdown
# Performance Optimization Plan
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## Problem
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The application lags severely when large files are open — even simple mouse movement causes noticeable frame drops.
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### Root Cause
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Every frame (triggered by any mouse event), Iced calls `shader::Program::draw()` → `build_primitive()`.
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This function:
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1. **Re-tessellates every entity from scratch** — `wires_for_block()` iterates all document entities and calls `tessellate_one()` for each, every single frame.
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2. **Recreates all GPU buffers** — `prepare()` calls `upload_wires/hatches/images/meshes()`, each of which allocates new `wgpu::Buffer` objects for every entity, every frame.
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3. **Linear-scans all objects** to find `SortEntitiesTable` on every frame.
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During pure mouse navigation (pan/zoom), nothing in the geometry data changes — only the camera matrix (uniforms) changes. Despite this, all work above is repeated for every mouse-move event.
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---
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## Option A — Wire Tessellation Cache ✅ Implemented
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**Status:** Done
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Added `wire_cache: RefCell<Option<(u64, Arc<Vec<WireModel>>)>>` to `Scene`.
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`entity_wires_arc()` checks the cache first; if `geometry_epoch` matches it returns the cached
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`Arc` (O(1) refcount bump). On a cache miss it tessellates, wraps the result in `Arc`, stores it,
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and returns a clone of the `Arc`.
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`build_primitive()` uses `entity_wires_arc()` directly:
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- **No preview wires (navigation):** stores the Arc as-is — zero Vec clones, zero tessellation.
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- **Command active (preview wires present):** clones the cached entity Vec once, appends
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preview/interim wires, wraps in a new Arc — only one allocation instead of full tessellation.
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`Primitive::wires` changed from `Vec<WireModel>` to `Arc<Vec<WireModel>>`.
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**Impact:** During navigation in large files the per-frame cost of the wire step drops from
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O(entities × tessellation) to O(1). Combined with Option B the GPU upload is also skipped,
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making navigation frames nearly free regardless of file size.
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---
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## Option B — GPU Buffer Cache ✅ Implemented
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**Status:** Done
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Add a `geometry_epoch: u64` counter to `Scene`. Bump it whenever geometry-affecting state changes.
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Carry the epoch through `Primitive` to `Pipeline`, which stores `cached_epoch: u64`.
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In `prepare()`:
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- **Always** upload uniforms (camera changes every frame).
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- **Skip** geometry buffer uploads (`upload_wires/hatches/images/meshes`) when `geometry_epoch == cached_epoch`.
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- After uploading, set `pipeline.cached_epoch = geometry_epoch`.
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**Impact:** During navigation, only a single 192-byte uniform write reaches the GPU instead of
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re-creating thousands of buffers. Fixes mouse-movement lag in large files.
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**Difficulty:** Medium. Requires bumping the epoch in all geometry-mutation paths.
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### Epoch bump locations
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| Method | Location |
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|--------|----------|
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| `add_entity()` | `scene/mod.rs` |
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| `erase_entities()` | `scene/mod.rs` |
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| `populate_hatches_from_document()` | `scene/mod.rs` |
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| `populate_images_from_document()` | `scene/mod.rs` |
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| `populate_meshes_from_document()` | `scene/mod.rs` |
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| `set_preview_wires()` | `scene/mod.rs` |
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| `clear_preview_wire()` | `scene/mod.rs` |
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| `set_interim_wire()` | `scene/mod.rs` |
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| `select_entity()` | `scene/mod.rs` |
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| `deselect_all()` | `scene/mod.rs` |
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| `expand_selection_for_groups()` | `scene/mod.rs` |
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| `toggle_layer_visibility()` | `scene/mod.rs` |
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| `transform_entities()` | `scene/mod.rs` |
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| `copy_entities()` | `scene/mod.rs` |
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| `apply_grip()` | `scene/mod.rs` |
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| `clear()` | `scene/mod.rs` |
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---
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## Option C — Parallel Tessellation (Rayon)
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**Status:** Planned
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Replace the sequential `.flat_map(|e| self.tessellate_one(e))` chain in `wires_for_block()` with
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`rayon::par_iter()`.
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**Impact:** Spreads tessellation across all CPU cores. Improves file-open time and post-edit
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refresh. Does **not** fix per-frame navigation lag (Option A/B address that).
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**Difficulty:** Easy. Requires making `tessellate_one` free of interior mutability, or collecting
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into a Vec first then parallel-processing.
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---
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## Option D — Frustum / Viewport Culling
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**Status:** Planned
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Build a spatial index (R-tree or uniform grid) over entity bounding boxes.
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During `wires_for_block()`, skip entities whose bounding box lies entirely outside the camera frustum.
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**Impact:** Dramatic speedup for large drawings when zoomed in — only visible entities are
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tessellated and uploaded. No benefit when the full drawing is visible.
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**Difficulty:** Hard. Requires maintaining an up-to-date spatial index and computing per-entity
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bounding boxes for all entity types.
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---
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## Option E — SortEntitiesTable Scan Cache ✅ Implemented
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**Status:** Done
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Added `sort_cache: RefCell<Option<(u64, HashMap<Handle, HashMap<u64, u64>>)>>` to `Scene`.
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On the first call to `wires_for_block()` after a geometry change, the cache scans all
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`document.objects` once and builds an index: `block_handle → (entity_handle.value() →
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sort_handle.value())`. Subsequent calls within the same epoch do an O(1) HashMap lookup
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instead of the previous O(objects) `find_map` scan.
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The cache is keyed by `geometry_epoch` and invalidated automatically alongside the wire
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and GPU caches whenever geometry changes.
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