feat: add gltf-skin-roundtrip example witnessing the skinned export contract#88
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…ontract The geometry round-trip left the skinning side of the format uncovered: skeleton, weights, and deformation must all survive it. A seven-bone scorpion rig exported with export_skins and re-imported pins all three — joint list and unit weight sums on disk, bit-exact weights and rest matrices on re-import, identical deformation — plus the parenting hazard (unparented skinned meshes let the exporter bind an armature by name) and the sorted-multiset trap (the exporter welds duplicate loops; compare by rest-key). The skins pipeline is byte-identical on 4.5.11 and 5.1.2. Signed-off-by: fOuttaMyPaint <TMhospitalitystrategies@gmail.com>
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Summary
Second of two new examples (after #87): the glTF skinned-mesh export follow-up from the ROADMAP pool — a seven-bone mech scorpion exported with
export_skins=Trueand re-imported, witnessing the skinning contract the geometry round-trip left uncovered. Completes the pipeline arc: modeling/LOD → weighting → tangents → export → skins.Contract witnessed
skins[0].jointsnames all 7 bones; re-imported armature has same bones, same parent chain, rest matrices within 2.38e-07. The +Y-up conversion hits bone node translations exactly like meshes.Version witness: skins pipeline stable — exporter/importer RNA byte-identical (probed with
gltf-export-roundtrip), every measured value identical on both binaries.Falsification evidence (temporary breaks, restored after measurement):
export_skins=FalseContact-sheet gate: gltf-skin-roundtrip-contact-sheet.webp — verdicts: stage darkness ✓, wedge warmth ✓, subject fill ✓ (after a reframe pass), saturation ✓ (orange/teal), thumbnail legibility ✓ (twin scorpions with curled tails). Mean luminance 120.3 vs calibration 139.4 / 100.1 / 143.4 — inside range.
Proven by live run vs inspection:
.scratch/blender-5.1.2-windows-x64/blender.exe(Blender 5.1.2, hash ec6e62d40fa9) and.scratch/blender-4.5.11-windows-x64/blender.exe(Blender 4.5.11 LTS, hash 4db51e9d1e1e) — identical values (bones=7 verts=440 eval_loops=1224 disk_verts=1192 sum=2.98e-08 rest=2.38e-07 w=0.0 pos=4.77e-07). Render exit 0 on both binaries (EEVEE), pixels iterated (4 drafts: framing, claws, angle, fill). All probes live.Test plan
28 examples)examples/gltf-skin-roundtrip/gltf_skin_roundtrip.py --.scratch/blender-5.1.2-windows-x64/blender.exe(5.1.2),.scratch/blender-4.5.11-windows-x64/blender.exe(4.5.11 LTS)Integration: example dir + README (with pipeline-arc cross-references), gallery.json entry, plugin manifest, smoke step, top-level README ("Game asset pipeline" category now 5, counts 27→28), generated pages read character-by-character (alt and callout full), ROADMAP entry shipped-marked.
🤖 Generated with Kimi Code