Retopology

Clean, purposeful topology for deformation, UVs, and performance. Quad-dominant. Animation-ready.

When to Use

• After sculpting high-poly characters/creatures
• Before rigging any deforming mesh
• Poly reduction while preserving silhouette
• Fixing topology from boolean or scan cleanup

Workflow

High-Poly Reference → Guide Setup → Block Retopo → Loop Refinement
    → Pole Placement → Triangle Cleanup → Validation → UV Handoff

Retopology Methods

Method	Best For	Speed
Manual (Poly Build tool)	Hero characters	Slow, best quality
Shrinkwrap retopo	Creatures, organic	Medium
Quad Remesh (voxel)	Quick blockout retopo	Fast, needs cleanup
Instant Meshes (external)	Background assets	Fast
Symmetry retopo	Bilateral characters	Medium

Production default: Manual with shrinkwrap for hero; Quad Remesh + cleanup for background.

Edge Loop Rules

• Loops follow muscle/deformation direction
• One loop per major form change
• Maintain even edge length in deformation zones
• Redirect loops at poles (minimum 3 edges meeting)
• Hide poles at back of head, armpits, groin

Pole Management

Location	Acceptable	Avoid
Top of head	3–5 pole	—
Inner eye corner	Redirect pole	Pole directly at corner
Shoulder	3-edge pole hidden	Star pattern on deltoid
Back of knee	Pole in crease	Pole on front of knee

Triangle Policy

• Triangles OK on non-deforming static mesh
• Convert tris to quads on face, joints, fingers
• No n-gons on deforming surfaces
• Tris at hidden areas (scalp under hair, mouth interior)

Polycount Targets

See ../references/polycount-budgets.md. Retopo is where budget is enforced.

Shrinkwrap Retopo Setup

1. Duplicate high-poly to reference collection (hidden in render)
2. Create retopo mesh with Poly Build / manual extrude
3. Shrinkwrap modifier → Target: high-poly
4. Snap to face with project individual elements
5. Validate shrinkwrap distance (no intersection)

Validation Checklist

• Quad-dominant on all deformation areas
• Edge loops support planned rig joints
• No non-manifold geometry
• Silhouette matches high-poly reference
• Polycount within budget
• Poles placed at acceptable locations
• Mesh manifold and watertight (if required)

MCP Integration

1. Create retopo mesh object via MCP
2. Apply shrinkwrap modifier via MCP
3. Query face/edge count during retopo
4. Compare silhouette via MCP render/query
5. Transfer to COL_Geo_LowPoly collection

Constraints

MUST DO

• Retopo before rigging deforming meshes
• Preserve silhouette vs high-poly reference
• Plan loops for facial expressions (characters)
• Enforce polycount budget
• Validate manifold before UV pass

MUST NOT DO

• Auto-retopo without manual cleanup (hero assets)
• Leave n-gons on deformation surfaces
• Skip validation against reference
• Retopo without knowing rig requirements
• Uniform density (more density at face/hands)

Reference Guide

Topic	Reference	Load When
Facial retopo	references/facial-retopo.md	Character faces
Game vs cinematic	references/game-cinematic-topo.md	Budget decisions