Material Identity – Spectral (MI-S) v0.1

1. Purpose

MI-S (Material Identity – Spectral) defines a deterministic protocol for verifying material identity based on measured reflectance spectra (380–730 nm). Material identity is defined as energetic structure, not appearance.

2. Normative Basis

• Reflectance range: 380–730 nm
• Primary metric: λ*_V2 (energetic equilibrium)
• Root-finding: Brent method (deterministic, derivative-free)
• Atlas-only constraint: All references must exist in the official Atlas

3. Core Definitions

3.1 λ*_V2

Defined as the unique root of:

g(λ) = ∫₃₈₀^λ (1 − R(λ')) dλ' − ∫_λ^₇₃₀ R(λ') dλ'

λ*_V2 satisfies: g(λ*) = 0

3.2 λ*_EE

Energy centroid of reflected light.

3.3 Δλ*

Δλ* = λ*_V2 − λ*_EE
Indicates spectral asymmetry and metameric risk.

4. Spectral Windows

• calm – stable local structure
• pull – moderate directional bias
• tip – high sensitivity region
• break – structural discontinuity

5. Deterministic Atlas Mapping

All external inputs must be snapped to exactly one Atlas reference using ΔE₀₀ (D50 / 2°). No interpolation, no generation.

6. Workflow

1. Spectral acquisition
2. Preprocessing & validation
3. λ*_V2 computation (Brent)
4. λ*_EE computation
5. Δλ* analysis
6. Window classification
7. Atlas validation
8. Structured reporting (Hybrid Compact Schema)

7. Validation Layers

• Schema conformity
• Atlas existence check
• Physical plausibility
• Prompt logic compliance

8. Exclusions

• Not a color space
• Not a generator
• Not an optimization system
• No perceptual tuning