gn-bundle-roundtrip

Geometry Nodes bundle round-trip

Combine Bundle / Separate Bundle packing a cube plus Scale, Offset, and Mark — witnessing geometry-nodes-python item-name round-trip, not tree structure.

Which RNA, on which Blender

Blender	Combine / Separate RNA	Legacy GeometryNodeCombineBundle	This example
4.5 LTS	not defined	defined, but evaluates empty unless preferences.experimental.use_bundle_and_closure_nodes is on (default off)	skips, exit 77
5.0, 5.1, 5.2 LTS	NodeCombineBundle / NodeSeparateBundle	undefined — nodes.new raises RuntimeError: Node type GeometryNodeCombineBundle undefined	runs

If you are porting a 4.5 script to 5.x and nodes.new("GeometryNodeCombineBundle") raises "undefined", the 5.x id has no GeometryNode prefix: use NodeCombineBundle / NodeSeparateBundle. On 4.5 the reverse holds: NodeCombineBundle is undefined, and the legacy node can be created with the experimental flag off — it just evaluates to nothing, which is the easy trap. 4.5 API pages: GeometryNodeCombineBundle, PreferencesExperimental.

Every cell above was re-verified by probe on 4.5.11 LTS, 5.0.1, 5.1.2 and 5.2.1 LTS. On 4.5.11 the flag exists and reads False; a legacy Combine → Separate carrying a cube evaluates to 0 verts / 0 faces with it off and 8 / 6 with it on. On 5.0.1, 5.1.2 and 5.2.1 the flag is gone from PreferencesExperimental.

The catalog floor is min_version 5.0 and the example prints SMOKE_SKIP: Bundles require Blender 5.0+ (exit 77) below it. --force-run bypasses the skip and creates the 5.x RNA, so 4.5 fails for that reason — NodeCombineBundle undefined, caught by the FATAL wrapper as exit 1 — not a hidden pass. On 5.x --force-run changes nothing and exits 0.

What it witnesses

Closed form (1 m cube, Scale=2, Offset=(1.5, 0, 0), Mark=0.314159):

• verts/faces = 8/6
• x-extent [0.5, 2.5]
• POINT bundle_mark = 0.314159 on all 8 verts

Count alone is not enough. A cube that never entered the bundle is still 8/6 (--bypass). Bbox from the unpacked Scale/Offset is the second axis; the named attribute from the unpacked Float is the third. Each axis has its own falsifier, and each falsifier leaves the axes before it green, so it fails on the axis it names.

No gallery still. The contract is item names + typed round-trip; the visible mesh is one cube and the attribute is invisible. Failure would not read at thumbnail.

What failure each check would catch:

• exit 77 — Blender < 5.0 and not --force-run
• exit 2 — GeometryNodeCombineBundle on 5.x (--legacy-rna)
• exit 3 — item names do not pair, so Separate yields no geometry (--mismatch renames the geometry item → 0/0)
• exit 4 — count matches but the unpacked Scale/Offset did not arrive (--bypass, --pack-scale 1)
• exit 5 — count and bbox match but the Float item did not travel (--mismatch-mark renames only the Float item → bundle_mark 0.0)

Run

blender --background --python gn_bundle_roundtrip.py --
blender --background --python gn_bundle_roundtrip.py -- --force-run
blender --background --python gn_bundle_roundtrip.py -- --mismatch-mark

Exit codes

Per-script sequential checks. 9 is a valid check code; there is no rule against it. 77 is the smoke skip protocol, not a product check.

Code	Meaning
0	Success
1	Uncaught exception (FATAL wrapper); --force-run on 4.5 lands here
2	argparse / usage; carrier mesh rewritten; --legacy-rna on 5.x
3	Evaluated vert/face count off closed form (--mismatch)
4	Unpacked Scale/Offset x-extent off (--bypass, --pack-scale 1)
5	bundle_mark missing or off closed form (--mismatch-mark)
77	SMOKE_SKIP: Bundles require Blender 5.0+

Measured on 4.5.11 / 5.0.1 / 5.1.2 / 5.2.1:

Flag	4.5.11	5.0.1	5.1.2	5.2.1
(none)	77	0	0	0
--force-run	1	0	0	0
--bypass	77	4	4	4
--legacy-rna	77	2	2	2
--mismatch	77	3	3	3
--mismatch-mark	77	5	5	5
--pack-scale 1	77	4	4	4

The blender-smoke workflow runs the check on Blender 5.2 LTS (5.1 on the weekly cron, the needs-5.1 PR label, or manual dispatch) and skips on 4.5 LTS. Smoke does not pass --bypass, --legacy-rna, --mismatch, --mismatch-mark, or --force-run.