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CAD simulation: Parallelize meshing and solid recognition; feedback fixes #15849

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CAD simulation: Parallelize meshing and solid recognition; feedback fixes #15849

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bd0d543
Fix undefined volumes placed by the CAD converter's name filter
sawenzel Sep 19, 2026
88ee005
Skip CAD leaves that are open faces instead of solids
sawenzel Sep 19, 2026
4bb6941
Report why PyROOT is missing and fail --csg required on it
sawenzel Sep 19, 2026
fb070f7
Mesh the CAD volumes in parallel and show progress
sawenzel Sep 19, 2026
e716fcc
Report progress of the surface and CSG phases
sawenzel Sep 19, 2026
879586f
Recognise the CAD CSG candidates in parallel
sawenzel Sep 20, 2026
0fa8d01
Say what loading a large converted geometry costs
sawenzel Sep 20, 2026
5703257
Count the surface tier by what the cascade emits
sawenzel Sep 24, 2026
143b61d
Say that a converted geometry's payload paths are absolute
sawenzel Sep 24, 2026
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20 changes: 19 additions & 1 deletion Detectors/CADSupport/README.md
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Expand Up @@ -63,6 +63,13 @@ and falls through elsewhere. `required` stops with a report if any leaf cannot u
0.1. `--mesh-solid tgeo` emits ROOT's `TGeoTessellated`, which does not implement navigation;
use it only for a macro that must load outside O2.

Meshing and CSG recognition dominate the conversion of a large model, so both run one part per
process, over all cores. `--jobs N` sets how many; `--jobs 1` runs both serially in this
process. The triangles, the sidecars and `geom.C` are the same either way; the `shape_*.root`
files are written by the parent process in part order, so they do not depend on `--jobs` either.
A script that imports this module and asks for several jobs needs the usual
`if __name__ == "__main__":` guard.

The output folder holds:

- `geom.C`;
Expand All @@ -71,7 +78,13 @@ The output folder holds:
- `brep_*.brep` (with `--dump-brep`);
- `surface_report.json` (with `--surface-report PATH`).

The macro loads its payloads relative to its own location, so move the folder as a whole.
The macro names its payloads by absolute path, so a converted folder cannot be moved or handed
on as it stands. Rewrite the prefix before shipping one, and run from the directory the payload
folder sits in:

```bash
sed -i "s|<absolute conversion dir>/|payloads/|g" geom.C
```

`geom.C` exports `get_builder_hook_unchecked()`, which `o2-sim` calls, and
`build_and_export(const char* out_root = "geom.root", bool check = true, bool checkOverlaps = false)`
Expand All @@ -82,6 +95,11 @@ for standalone use:
(cd cad_out/excavator && root -l -b -q -e '.L geom.C' -e 'build_and_export("geom.root", true, true);') # also CheckOverlaps
```

`checkOverlaps` costs far more than the load itself on a large model, so leave it off unless
you are looking for overlaps. Measured on the 140-part OuterDisc, 5.4M triangles: 1.3 s to
parse the macro, 15.7 s to build it (the payloads and their BVHs), 0.0 s to close the
geometry, 11.7 s to export, and 513.8 s for `CheckOverlaps`.

Other conversion options:

| option | meaning |
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