UnityLaparoscopicSceneSimulator/.claude/commands/pbr-materials-tissue.md

PBR Materials for Tissue (project-scoped)

Constrains material work to a small, deliberate set of tissue-like PBR patterns. The material inventory is fixed; the goal is to tune them, not multiply them.

When to use

Load before creating, editing, duplicating, or assigning any .mat under Assets/Materials/LaparoscopicBenchmark/, or diagnosing "plastic-looking tissue", "mucosa too dry", "specular too harsh", or "normal map stretched" reports.

Material inventory (do not duplicate blindly)

Material	Purpose	Tunable axes
Tissue_Default.mat	"Clean" tissue reference	roughness, normal scale, albedo tint, AO
Tissue_Wet.mat	Wet specular variant for Scenario_02	higher specular tint, lower roughness, slight clearcoat
Tissue_LowTexture.mat	Low-texture variant for Scenario_03	uniform albedo, minimal normal, low contrast
CavityWall.mat	Moist wall of the cavity	roughness, normal scale, subsurface tint, specular tint
InstrumentProxy.mat	Instrument placeholder	metalness 1.0, low roughness, neutral albedo

New variants: add to Assets/Materials/LaparoscopicBenchmark/ with name ending in scenario tag, e.g., Tissue_Wet_S04.mat. Do not rename the five canonical materials.

Available textures

• Assets/Textures/LaparoscopicBenchmark/TissueMucosa.png — canonical mucosa base map.
  • sRGB: on. Alpha Source: None. Max Size: 1024 (or 2048 for hero work). Compression: BC7/ASTC.
• Assets/Models/FabOrgans/StylizedDigestiveSystem_{Diffuse,Normal,Roughness}.png — stylized organ set.
• Assets/Models/organs/textures/ and archive.fbm/ — do not move (FBX references by relative path).

URP/Lit PBR defaults for tissue

• Shader: Universal Render Pipeline/Lit (metallic workflow, opaque surface).
• Render Face: Front. Double Sided: off (except cavity wall when viewed from inside).

Property	Tissue_Default	Tissue_Wet	Tissue_LowTexture	CavityWall	InstrumentProxy
Base color	warm pink-red ~#B66A6A	warm pink-red	uniform pink-red	deep red ~#7A2A2A	neutral metal ~#C8C8C8
Metallic	0.0	0.0	0.0	0.0	1.0
Smoothness	0.35	0.55	0.20	0.40	0.85
Normal Map	TissueMucosa normal	same	none / flat	cavity bump at low scale	none / flat
Normal Scale	0.5–1.0	0.5–1.0	n/a	0.3–0.7	n/a
Emission	off	off	off	off	off

These are starting points, not finals. Confirm by screenshot.

Diagnosis guide

Symptom	Likely cause	Fix
Tissue looks plastic	_Smoothness too high	Lower to 0.25–0.35
Mucosa too dry	_Smoothness too low	Raise to 0.4–0.5
Specular too harsh	_Metallic > 0 on tissue	Set _Metallic to 0
Normal map stretched	UV scale mismatch	Adjust material tiling, not mesh scale
Tissue reads as emissive	Emission on	Set Emission to black

Hard limits

• Never set Metallic > 0 on tissue or cavity wall.
• Never set Emission > 0 on tissue.
• Never use Standard (Built-in) shader.
• Never use procedural textures without explicit approval.
• Never rename the five canonical materials.
• Never create a material with a clinical term in the name.

Common MCP calls

# Read a material
mcp__UnityMCP__manage_material(action="get_material_info", material_path="Assets/Materials/LaparoscopicBenchmark/Tissue_Default.mat")

# Set a property
mcp__UnityMCP__manage_material(action="set_material_shader_property", material_path="...", property="_Smoothness", value=0.42)

# Set a colour
mcp__UnityMCP__manage_material(action="set_material_color", material_path="...", property="_BaseColor", color=[0.71, 0.42, 0.42, 1.0])

# Assign to renderer
mcp__UnityMCP__manage_material(action="assign_material_to_renderer", material_path="...", target="...", search_method="by_name", slot=0)