The post-slice thumbnail loaded the sliced 3MF with trimesh, whose reader
mishandles the Bambu Studio / OrcaSlicer layout: for every component that
references a file in 3D/Objects/ it re-parses that file and appends all
of its meshes again. N copies of a part came back as N^2 copies of its
triangles, and each component carried every other part of the same file.
25 bins of 10k faces loaded as 6.4M faces; the render took 54 s and
8.4 GB on the event loop, and the server was OOM-killed.
Parse the 3MF directly (lxml, entities/DTD/network off, streamed and
freed element by element), walk objects, components and build items
(p:path on either) with their transforms, and keep each mesh once.
Decimate per unique mesh to its share of a face budget before placing
instances, flip winding on mirrored placements, and skip the thumbnail
above a face ceiling checked both on what decimation can reach and on
what it delivered.
Both slice routes run the render in a thread. The renderer uses
matplotlib's Figure/Agg API instead of pyplot, whose process-global
figure state let a threaded plate render and stl_thumbnail's
event-loop render lay out and close each other's figures.
Bambuddy's archive cards were blank for every print sliced through the
BS or Orca docker sidecars. The "Some recent prints couldn't be archived
with thumbnails" banner pointed at install step 4 which is unrelated —
that flag only fires on FTP-fetch failures, not on missing-thumb in the
sliced 3MF.
Root cause is upstream of Bambuddy: neither slicer CLI renders
Metadata/plate_N.png when invoked headlessly with --slice --export-3mf.
That render is a separate code path triggered by --export-png, which is
mutually exclusive with --export-3mf and additionally needs a working
display backend (BS 02.07.x's bundled GLFW is hard-locked to Wayland —
even XDG_SESSION_TYPE=x11 + GDK_BACKEND=x11 + QT_QPA_PLATFORM=xcb don't
switch it back). An Xvfb display in the sidecar wouldn't help even if we
wired the second-pass call. The Orca sidecar has been silently shipping
thumbnail-less 3MFs from STL inputs since launch; nobody noticed.
Fill the gap on the Bambuddy side: new plate_thumbnail.py renders the
missing thumbnails after the slice returns. inject_plate_thumbnails_if_missing
parses the sliced zip, finds every Metadata/plate_N.gcode entry that
doesn't have a matching plate_N.png, loads 3D/3dmodel.model via trimesh,
renders an isometric Bambu-green-on-dark view at 512x512 + 128x128 via
the same matplotlib Agg pipeline as stl_thumbnail.py, and re-packs the
zip with the PNGs injected. Visual style matches Bambuddy's existing
library thumbnails — archive cards stay consistent inside Bambuddy rather
than chasing parity with desktop Studio's plate render. Best-effort:
input bytes are returned unchanged on any failure so the slice flow itself
can never fail because of a missing thumbnail. Idempotent: re-running on
an already-injected 3MF returns the input verbatim.
Wired into both library.py slice paths via result._replace; covers the
cross-class merged-multi-plate path automatically (merged bytes flow into
the same write site). No sidecar Dockerfile change required — an earlier
attempt to install Xvfb in Dockerfile.bambu-studio was a false start and
is not part of this drop.
Dependencies: trimesh's 3MF loader uses networkx (scene-graph traversal)
and lxml (model.xml parse) lazily inside the 3MF code path — both added
to requirements.txt because they aren't strict trimesh transitives.
maziggy