Scene analysis

Three tools extract an evaluated snapshot of the scene, called SceneIR, and analyze it with a small Rust runtime:

.blend or export
  → Blender extraction → SceneIR
  → bas-runtime → description and quality report

baseline + candidate SceneIR
  → bas-runtime → structural diff and declared gates

They make hierarchy, dimensions, topology, and explicit constraints queryable. They don't measure aesthetic quality.

#Describe, then focus

Start with blender_describe_scene and an assetPath. It returns object IDs, authored roles, mesh counts, evaluated world-space bounds, the hierarchy, and bounded spatial candidates. Then focus on one assembly:

{
  "assetPath": "/assets/deer.blend",
  "frame": 24,
  "objectId": "deer",
  "includeDescendants": true,
  "limit": 40
}

• IDs are exact Blender object names. Roles come only from an authored bas_role custom property, never from names.
• frame evaluates a pose without saving the file. It doesn't bake simulations.
• Results are paginated, but bounds and constraints always cover the whole selection.

#Check explicit constraints

blender_quality_report checks only the constraints you ground in the brief:

{
  "assetPath": "/assets/deer.blend",
  "objectId": "deer",
  "triangleBudget": 2500,
  "groundZ": 0,
  "groundObjects": ["front_left_hoof", "front_right_hoof"],
  "requireClosedMesh": false
}

Use contactPairs for parts that must touch and connectionPoints for joints such as pivots and cable ends. Triangle budgets, required closed meshes, and definite contact gaps fail. Open edges, disconnected parts, and overlapping bounds are findings to review.

A review_required status is not a pass. The report's visual questions still need an answer.

#Compare a repair

After regenerating a repair, blender_compare_scenes diffs the preserved baseline and the candidate. It reports added, removed, and changed objects, triangle and bounds deltas, and per-object transform and hierarchy changes. Matching uses exact IDs, so keep object names stable.

The diff states facts, not a verdict. Failures come only from options you declare, such as requiredObjects, forbidRemovedObjects, maxTriangleIncrease, or invariantObjects for parts the repair should leave alone.

#Limits

• Overlapping bounds are a candidate, not a proven intersection. Parenting doesn't prove a physical connection.
• Only meshes get geometry summaries. Instances are reported as omitted until realized.
• Symmetry, support, and semantic correctness aren't inferred.

The SceneIR guide covers the schema, every option, and size limits.