MCP backend

Use when: Multi-view validation and iterative fitting against reference templates, all-dimension mascot/object reconstruction, front/side/back/top overlay reports, fit deltas, automated adjustment loops.

Before the first Blender call, read ../text-to-blender/references/mcp-backends.md. Prefer official MCP for shared capabilities; preserve the selected backend for the whole task. Tool names in recipes are client/legacy examples: map them through that reference and its agent-host guide.

Multiview Fit Loop

This skill closes the missing loop: render → compare → adjust → render again. It is mandatory when a user says the model still does not fit the templates/originals.

Required loop

1. Render flat, material-independent silhouettes for every available template view: front, side, back, top.
2. Extract the template object mask, excluding labels, cyan guides, and background.
3. Compare template vs render per view:
   • bbox center and size
   • centroid drift
   • silhouette coverage/IoU where modality is valid
   • visual overlay
4. Convert measured deltas into model/camera/recipe adjustments.
5. Rebuild or transform the model.
6. Repeat until all hard gates pass or document the remaining conflict.

Constraint inconsistency gate

Before forcing adjustments, check whether the supplied orthographic templates are mutually consistent. A single rigid 3D model cannot simultaneously satisfy contradictory physical ratios, for example if side view says total depth is 0.39 of height but top view says depth is 0.98 of width. When this occurs, stop claiming final fit, write a conflict report, and create separate variants or ask which view is canonical.

Hard gates

• all required views have validation reports and overlays;
• bbox center drift <= 1.5% of image width;
• bbox size drift <= 3% for front, <= 5% for side/top/back first-pass depth;
• structural part count exact;
• texture UV regions still valid after geometry changes.

View mask rule

For annotated wireframes, choose a template mask mode that isolates the intended construction/object lines and excludes guide colors, labels, captions, and background annotations. For Blender validation renders, use a flat white silhouette on black, not beauty renders with glow/context elements.

Scripts

• scripts/multiview_fit_report.py compares view pairs and writes JSON + overlays.

Adjustment rule

Prefer changing recipe parameters or source geometry over camera scale tricks. Camera scale may be used only after model dimensions are correct.