The execution model is in blender-core. Material wiring and measured values are in blender-pbr-materials, and bakes are in blender-texture-baking. This skill authors the surface story: where paint chips, where dirt collects, what's printed on it.
One call each
scripts/smart_material.py -- --objects Crate --wear 0.5 --grime 0.4 --dust 0.3
scripts/smart_material.py -- --objects Crate --rust 0.6 --under-color 0.3 0.29 0.28 # rusty iron
scripts/smart_material.py -- --objects SM_Crate --wear 0.5 --curvature-map //tex/T_Crate_CURV.png --ao-map //tex/T_Crate_AO.png
scripts/decal.py -- --target Wall --at 0 -0.1 1.5 --image //decals/hazard.png --size 0.4
scripts/smart_material.py -- --objects Crate --remove # exact restore
How pros layer a material
Start with a clean base (correct albedo/roughness, blender-pbr-materials), then stack from the inside out: base → edge wear → rust → grime → dust. Each layer has a physical cause:
| Layer | Mask (cause) | Look |
|---|---|---|
| Edge wear | convex curvature (edges get hit) + chip noise | reveals the under-material: bare metal, primer, raw wood |
| Rust | cavities and worn edges + blotch noise | orange-brown, metallic 0, roughness ~0.85 |
| Grime | concave curvature + (1 − AO) (dirt collects where it can't be wiped) | dark, rougher, not metallic |
| Dust | world up-facing normal × patch noise (it settles from above) | light, roughness ~0.9 |
| Breakup | fine noise on roughness (±25%) | the cheapest realism win; never ship a flat roughness value |
| Pure curvature looks procedural and even. Always multiply in noise so wear is heavy in some places and absent in others. Less is more: wear 0.2–0.4 reads as "used", and 0.7+ reads as "abandoned". |
smart_material.py
- Inserts one
TX_Layersgroup in front of every Principled BSDF (Base Color, Roughness, Metallic) and records the originals, so--removerestores links and values exactly. Re-running updates values in place. All layer amounts stay inputs on the group node, so you can tweak them there. - Curvature, live and portable (Cycles + EEVEE, no bake): the
TX_Curvaturepoint attribute is the mean elevation of the neighbours within--edge-width(m, default 0.02). It's density-independent: band ≈ edge width. Set the width to roughly the bevel width (1–3 cm on props, 5–10 cm on buildings). Cost: ~1.5 s per 30k verts. - It needs mid-poly density (bevels/supports). When the median edge is > 4× the edge width, the result carries a
note: wear would smear across whole faces. On low-poly game meshes, bake from the high (bake_maps.py --high ... --maps normal ao curvature) and pass--curvature-map/--ao-map(loaded as Non-Color, read through--uv). - Noise is in object space (
--scale= feature size in m), so masks stick to the asset when it moves. Mirrored/linked duplicates share the pattern, so vary--scaleor the object if that shows. - Colors are sRGB 0–1. Defaults: steel under paint (0.56, 0.57, 0.58, metallic 1, roughness 0.35). For wood under paint, use
--under-color 0.45 0.32 0.2 --under-metallic 0 --under-roughness 0.7.
To game engines
Engines don't run Blender node trees. Bake the result into a texture set: bake_maps.py -- --low SM_Crate --maps basecolor roughness metallic normal --pack-orm (self-bake, no --high). Then build_pbr_material.py --textures and export. Check the result with blender-asset-qa and a lit look.
Decals (decal.py)
- Places a subdivided plane at the closest surface point to
--at, oriented to the normal and spun by--rotation. A Shrinkwrap (project, above surface) keeps it--offset(2 mm) off the surface. It's parented, has no shadow, uses Dithered alpha, and its height follows the image aspect. - It measures the gap at every triangle like
blender-asset-qadoes, and doubles--subdiv(to 128) until flat triangles stop dipping over convex creases. The result reportsgap_min_m/gap_max_m. Never place decals at 0 offset: that's guaranteed z-fighting. - Games: mesh decals cost a draw call each and need alpha sorting. Merge decals that share an atlas into one mesh, use engine projectors (UE Decal Actor, Unity URP Decal Projector, Godot
Decal) for dynamic ones, or bake them into the base texture.
Trim sheets, tiling, painting
Trim sheets, tiling with vertex-color blends, hand/texture painting (5.2 brush assets) and headless pixel writes: references/trims-tiling-painting.md.
Gotchas
- Mask textures (curvature, AO, roughness, ID) must be Non-Color. The script forces it, but hand-made nodes often don't.
- Apply scale before computing curvature or setting
--scale. Both are world-sized. TX_Curvatureis mesh data. Applying modifiers or remeshing afterward invalidates it, so re-run after topology changes.- Viewport EEVEE vs Cycles: identical masks (no Bevel/Pointiness/AO shader nodes are used, because those are Cycles-only or screen-space).