Jérôme Bousquié
57 lines
4.1 KiB
Markdown
57 lines
4.1 KiB
Markdown
# WSG - WGPU Simple Graphics Library
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## Project Type
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Rust workspace (2024 edition) wrapping [wgpu](https://github.com/gfx-rs/wgpu) for simple 3D drawing operations.
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## Workspace Structure
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```
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Cargo.toml # workspace root (members = ["lib"]) — no dependencies here
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lib/Cargo.toml # wsg-lib crate: wgpu 30.0.0, winit 0.30 + explicit [[example]] entries
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lib/src/ # library source (app, core/, mesh/, pipeline/, resources/, scene/, utils/)
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lib/examples/ # examples, one subfolder per category (each folder has a README.md):
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│ ├── meshes/ # simple, cube, pbr, import, manual
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│ ├── lights/ # shadow, shadow_test, spot_test, emissive
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│ ├── cameras/ # culling
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│ └── effects/ # demo, bloom, hdr, msaa, fog, dof
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```
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**Key convention**: examples live in `lib/examples/<category>/` subfolders. Cargo only auto-discovers top-level `examples/*.rs`, so **every example is declared explicitly in `lib/Cargo.toml`** (`[[example]] name = … path = "examples/<cat>/….rs"`). Names are stable: `cargo run -p wsg-lib --example <name>` works as before. Do not publish this to crates.io as-is — it uses local path conventions.
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## Essential Commands
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| Action | Command |
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|--------|---------|
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| Build everything | `cargo build --workspace` |
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| Run an example | `cargo run -p wsg-lib --example <name>` |
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| Run a feature-gated example | `cargo run -p wsg-lib --example import --features import-obj` |
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| Test | `cargo test --workspace` |
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| Check | `cargo check --workspace` |
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| Format | `cargo fmt --all` |
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No custom scripts or linting tooling beyond standard Cargo conventions.
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## Architecture Overview
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The library's purpose is to abstract the five core wgpu objects into a single **Context**:
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- **Instance** — GPU backend selection (Vulkan/Metal/DX12)
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- **Surface** — window rendering surface (via winit)
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- **Adapter** — physical/logical GPU device
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- **Device** — buffer/texture/pipeline creation
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- **Queue** — command submission
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WGPU doesn't have a native "Context" object — this type groups them together for a simpler user API. See README.md for the French documentation of each component.
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## Gotchas
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- Rust 2024 edition is used. Ensure your Rust toolchain supports it (`rustup update`).
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- wgpu 30.0.0 is pinned in `lib/Cargo.toml`. The comment says "check the latest version" — verify compatibility before upgrading.
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- Cargo features gate primitives (`prim-*`, `all-prims` is default) and importers (`import-obj`, `import-gltf`); the `import` example is `required-features = ["import-obj"]`. 127 tests exist (`cargo test --workspace`).
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- The workspace has no `[workspace.dependencies]` section. Dependencies are declared per-crate rather than centrally.
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- **WGSL `select` argument order** (cost us a day): `select(reject, accept, cond)` returns the **second** arg when `cond` is true — the reverse of HLSL's `select(trueVal, falseVal, cond)`. In `shaders/gpu_driven.wgsl` the cull pass must stay `select(0u, u32(flags.z), visible)` (visible ⇒ full count, culled ⇒ 0). Swapped args silently zero the counts of every visible entity → black window. See the GOTCHA comment at the top of that shader.
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- **LOD UV blending: never fold integer-tile jumps, freeze seam twins instead** (cost us a day, 2026-09-23): a UV *seam* is two copies of the same 3-D point on integer-apart UVs (u=0/u=1 columns) — it is NOT a mesh edge, so the decimation must record the weld's refused pairs and **freeze** those twins (any edge touching one is excluded from the PQ). A co-facial edge spanning a whole tile (cone apex v=1 ↔ base v=0) is a *legit* chart span — the chart is bilinear, so the UVs **blend linearly** (fold the integer jump to zero and the apex UV smears down the cone side). And the attribute-aware weld refuses a Δ of *exactly* 0.5 (ambiguous: seam at its widest vs legit half-tile jump — the cone's u=1 column vs the cap-disc chart sits exactly there). See the comments in `geometry.rs` (`welded`, `Collapse::collapse_edge`) and the cone/seam regression tests.
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<!-- lean-ctx -->
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## lean-ctx
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Prefer lean-ctx MCP tools over native equivalents for token savings.
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Full rules: @LEAN-CTX.md
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<!-- /lean-ctx -->
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