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Verify Blender connector connectivity

Smaller than it sounds, but it's the prerequisite for everything else.

started 2026-05-07 · updated 2026-05-09 · repo →

What I was trying to do

Before I commit to letting Opus drive Blender for the next Halloween project, I needed to know two things actually worked end-to-end: (1) can the model query the current scene and get back an honest summary of what’s in it, and (2) can it render a thumbnail of a specific viewport and see the result. If either of those fails, the rest of the pipeline isn’t worth building.

How Opus helped

Opus wrote the smoke-test harness in about ten minutes — a Python script that calls get_objects_summary, then render_thumbnail_to_path, then loads the resulting PNG and asserts on its dimensions. It caught a missing mathutils import that the wrapper needed (I’d have spent fifteen minutes on that one) and structured the test as a series of independently-debuggable steps with clear failure messages.

What went sideways

The connector was timing out on the first run. Turned out the Blender process was waiting for me to dismiss a “save changes?” dialog from the previous session. Twenty minutes lost staring at terminal output, then I switched to the Blender window and there it was, blinking patiently. Filed a mental note to start every session from a clean file.

Result

Both calls work. Scene summary is accurate (including object types, vertex counts, material references). Thumbnails render to the expected path at the resolution I ask for. Total project time: two evenings, mostly the dialog incident.

Now I can move on to the actual fun thing, which is letting Opus design a procedural rig for the projection-mapped orb.

  • Source: see repo link above
  • Smoke test: tests/smoke_test.py

The harness is intentionally boring:

python
summary = client.call("get_objects_summary")
assert summary["object_count"] >= 0

thumb = client.call("render_thumbnail_to_path", path="/tmp/smoke.png")
assert thumb["width"] == 512

Knotable Mentions

  • Anthropic Opus 4.7 — Wrote the smoke-test script and caught a missing addon dependency
  • blender-mcp — The MCP wrapper around Blender's Python API
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