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Blender is now a mandatory stage in draupnir's pipeline (Prime, 2026-09-28), and draupnir asked for eight add-ons from extensions.blender.org: SurfacePsycho 0.10.4, CAD Sketcher 0.32.1, 3D-Print Toolbox 1.4.1, STEP Importer 1.2.1, Bool Tool 2.1.0, LoopTools 4.7.7, MeasureIt 1.8.4, 3MF Import/Export 2.7.7. - stacks/blender/extensions.lock pins each by version and archive sha256. - scripts/blender-extensions sync builds fv-ml1:/tank/blender-extensions/5.2/system with Blender's own install-file, pre-warms and byte-compiles it, checks a read-only enable, then swaps it in. It refuses while the GUI or a blender-run job holds the old directory. - conf/scripts/startup/fleet_extensions.py enables every package in the System repo: in a timer in the GUI (after the prefs load), and as --python ahead of the caller's args in blender-run --extensions (a failed enable exits 1 before the caller's script). - It also patches SurfacePsycho's sp_overwrite_segment_selection from eval() to literal_eval(): the eval walked past MCP safe mode (control: unpatched ran code, patched refuses). - blender-run: --extensions (bind mounts via --mount so a missing source fails instead of being created); USER/LOGNAME set, which CAD Sketcher's getpass needs. - compose.yaml mounts the repo read-only and the hook into the GUI container. NOT yet deployed. - scripts/blender-probes/extensions_acceptance.py: one operator run per add-on, safe-mode compliant. Headless 8/9 online and with --network none; CAD Sketcher sketching is GUI-only. A Python audit hook saw no network/process events (positive control fired).
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Blender: headless and agent-driven 3D on fv-ml1 GPU 3
Blender 5.2.2 LTS (bundled Python 3.13), runs on fv-ml1 GPU 3 (RTX PRO 6000 Blackwell,
96 GB). Stack and full notes: /home/lkraven/development/eshpfi-management/stacks/blender/README.md.
⚠ GPU 3 is borrowed. It is the fleet's reserve card for a full-size vLLM seat. Blender runs only while in use, and this access ends if a big seat moves onto the card.
Two ways in
| You are… | Use | Shape |
|---|---|---|
| a script or CLI caller (renders, conversions) | scripts/blender-run |
one-shot docker run --rm: no desktop, gone when Blender exits |
| an agent building scenes interactively | scripts/blender-mcp (MCP, per task) |
a GUI Blender plus the mcp-for-blender add-on; up / status / down |
Both scripts are in /home/lkraven/development/eshpfi-management/scripts/ and run from nh3-dev,
reaching fv-ml1 as infra-ops@10.251.50.54 over ssh. No HTTP API and no openapi.json.
blender-run (headless)
scripts/blender-run --job /path/to/jobdir -- --python render.py -- out.png
scripts/blender-run --extensions --job /path/to/jobdir -- --python model.py
scripts/blender-run -- --python-expr 'import bpy; print(bpy.app.version_string)'
- Always adds
-b --factory-startup --python-exit-code 1. Arguments go after--. - Files: fv-ml1 does not mount
/mnt/smithy.--job DIRmirrors DIR tofv-ml1:/tank/blender/jobs/<basename>-<hash of DIR's absolute path>/, runs with that as the working directory, and copies new or changed files back into DIR. Nothing is ever deleted locally, and a rerun starts from an exact mirror, never from leftovers. Use relative input paths inside the job. Do not run the same DIR twice at once. - Engines headless (tested 2026-09-28): Cycles on GPU (OptiX/CUDA), Cycles on CPU, EEVEE
(EGL, no display needed, ~9 s with the shader compile on first use), Workbench. In 5.2 the
EEVEE id is
BLENDER_EEVEE(BLENDER_EEVEE_NEXTis gone). For Cycles GPU, setprefs.compute_device_type = 'OPTIX'and enable the OPTIX devices, thenscene.cycles.device = 'GPU'. Factory startup defaults to CPU. - Import: STL is built in (
bpy.ops.wm.stl_import). STEP, 3MF and the other add-ons need--extensions(below). --extensionsenables the pinned add-on set: SurfacePsycho 0.10.4 (NURBS patches, STEP/IGES export via its bundled OCP), CAD Sketcher 0.32.1, 3D-Print Toolbox 1.4.1, STEP Importer 1.2.1, Bool Tool 2.1.0, LoopTools 4.7.7, MeasureIt 1.8.4, 3MF Import/Export 2.7.7. Pins:stacks/blender/extensions.lock. If any add-on fails to enable, the run exits 1 before your script starts. It adds a few seconds of startup (the add-on wheels unpack per run), so it is off by default. CAD Sketcher's sketch operators need the GUI (they activate a workspace tool); headless they fail with "'NoneType' object has no attribute 'widget'". Operators that want a 3D View (MeasureIt, LoopTools) take abpy.context.temp_override(area=...)with a screen datablock's VIEW_3D area. Worked calls for every add-on:scripts/blender-probes/extensions_acceptance.py. Full notes and foot-guns: the stack README, section "Extensions".- Budget: each run is capped at 64 GB RAM and 48 CPUs, with up to the whole 96 GB of VRAM. Keep to about 2 concurrent renders. It is not on irv-ml1, so irv-ml1's working-set budget does not apply.
⚠ Foot-guns (all measured):
- A
--pythonscript that raises exits 0 unless--python-exit-codeis set. blender-run sets it. render.filepathmust be absolute. Blender does not resolve a relative output path against the working directory ("cannot save 'out.png'"). Importers and Python file I/O do.- Harmless stderr noise: "HIPEW initialization failed" (the AMD backend probing), and "Failed to create secure directory (/defaults): Operation not permitted" (the image's runtime-dir setup running as a non-root user; reported by draupnir 2026-09-28).
- The first OptiX render in a process includes about 1-2 s of kernel load.
blender-mcp (agents)
Register it per task, never user- or project-wide (Prime, 2026-09-27):
claude mcp add blender -- /home/lkraven/development/eshpfi-management/scripts/blender-mcp.
Then run scripts/blender-mcp up, wait for status to say answering, work, and run down
when finished. Safe mode is on (no os/open/network in agent code), so the startup hook has
already pointed Cycles at OptiX. Save to /work/…. Details and traps are in the stack README.