44 lines
2.0 KiB
Markdown
44 lines
2.0 KiB
Markdown
# The kernel boundary and truck
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`crates/kernel` is SolidCraft's B-rep kernel. It wraps
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[truck](https://github.com/ricosjp/truck) (Apache-2.0) for topology, NURBS geometry, booleans,
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tessellation and STEP parsing, and it is the only crate allowed to use truck. Callers get
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SolidCraft types (`Body`, face and edge indices, meshes, measures) and a
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`KernelError` instead of truck types and panics.
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## `guard`
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truck can panic on geometry it doesn't handle. Every call into it goes through
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`solidcraft_kernel::guard`, which catches the panic and turns it into
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`KernelError::Internal`, leaving the model unchanged:
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```rust
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pub fn guard<T>(what: &str, f: impl FnOnce() -> Result<T>) -> Result<T>
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```
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A failing feature shows an error on the timeline; it never takes the app down.
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## What is our own
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truck has no fillets, chamfers, shells or face edits, so these are SolidCraft code in the
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kernel: constant, chord and variable-radius fillets with corner blends, chamfers, shell and
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offset, Delete Face, Split Face, Replace Face, sewing, STEP and IGES reading and writing beyond
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truck's parser, and face provenance (which input face each output face came from, for
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[persistent naming](naming.md)).
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## Vendored truck crates
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Patched copies of `truck-shapeops`, `truck-stepio` and `truck-meshalgo` live in `vendor/`,
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wired in with `[patch.crates-io]`. The patches fix robustness bugs found by our tests and the
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STEP corpus. `vendor/` is excluded from our fmt and clippy rules, and each patch should go
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upstream when it can.
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Equal cylinders crossing each other (`tangent_cylinders.rs`) touch at two points, which truck's
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mesh-based intersection cannot trace through. When a boolean of such a pair fails, the kernel
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splits both cylinder faces along the line through the touching points and takes the boolean of
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the split bodies; the shapeops patch that picks the corner of a face at a vertex several curves
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end on makes the arms of the crossing connect.
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Some truck assertions only run in debug builds and can fail on valid geometry, so tests and CI
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run with `--release`.
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