3D Character Rigging Brief Generator

3D Character Modeling & Rigging Technical Brief

1. Project Overview & Scope

Character Concept: Stylized cyberpunk samurai girl with a high-tech robotic right arm and a loose-fitting streetwear coat. Hand-painted or stylized PBR look, with clean silhouettes and readable shapes at mobile screen size.

Target Platform/Engine: Unity (URP, mobile) with Blender as the source/authoring tool. Final assets must import into Unity with no manual fixing, and the Blender source must be clean enough for later edits.

Primary Function: Playable hero character for a third-person action mobile game, with dialogue cutscenes (facial animation needed).

2. Geometry & Topology Specifications

Polygon Budget: Hard limit of 35,000 triangles for the full character (body, coat, robotic arm, hair, accessories, weapon if included). Suggested allocation:

Triangle count must be shown with Blender's Statistics overlay in the review screenshots. No hidden or unused meshes in the final file.

• Topology & Edge Flow:
  • All-quad base mesh is preferred, with triangulation only where needed.
  • At least 3 edge loops at the knees, elbows and shoulders, with 2 loops at the wrist and ankles.
  • Radial loops around the mouth and eyes (3+ loops each), with edge flow following the facial muscles for clean blendshape deformation.
  • The coat must have vertical edge flow with enough horizontal loops in the hem area for smooth bending around the secondary bones.
  • Robotic arm: mechanical parts stay rigid (non-deforming). Only the organic joint areas (shoulder, upper arm blend) use deformation loops.
  • No n-gons, no non-manifold geometry, no interior or hidden faces, and no overlapping vertices.

Scale & Unit Setup: Metric, 1 unit = 1 m (Unity-correct scale at 1.0 on import). Character height about 1.65–1.7 m. Apply all transforms (scale 1, rotation 0) before export. Neutral

A-pose (about 30–45° arm angle) with feet at world origin, facing +Y in Blender (forward in Unity after export).

• UVs & Materials:
  • One non-overlapping UV set (UV0) with a consistent texel density.

Maximum 3 materials: (1) body, face and clothing atlas, (2) robotic arm and metals, (3) hair/transparency or emissive parts if needed.

• Texture resolution: 1024×1024 (head/face area may use 2048×2048 if justified), with power-of-two sizes only.
• Texture maps: Base Color, Normal (OpenGL/Unity-compatible), and a packed Metallic/Smoothness map, plus Emission for the cyberpunk glowing parts.
• Materials must be compatible with Unity URP (Lit or Simple Lit shader). Mobile-friendly: no heavy transparency, and alpha cutout only for hair if needed.

3. Skeletal Hierarchy & Body Rigging

Core Skeleton Architecture: Unity Humanoid-compatible biped (Mixamo-style naming or standard Humanoid bone names), so the Humanoid Avatar configures cleanly and animation retargeting works. Single root bone, about 20–25 core bones, with all extra bones (cloth, arm mechanics) parented under the humanoid bones and not breaking the avatar mapping.

• IK/FK Controls:
  • Blender control rig with IK/FK switching on both arms and legs, pole vector targets for the elbows and knees, and foot roll controls.
  • Spine FK controls (3 segments) plus neck and head controls.

Important: control rigs stay in the Blender source file. The exported FBX contains

deform bones only (clean hierarchy, no control or helper bones), because Unity handles IK separately.

Deformation & Twist Bones: Twist bones on the upper arms, forearms and thighs (1 per segment) to prevent candy-wrapper collapse at the wrists and shoulders. For the robotic arm, the forearm twist should be mechanically plausible (e.g., a rotating hand ring).

• Secondary Dynamics:

Coat hems: secondary bone chains (2–3 bones per chain) with 8–12 chains total spread around the front, sides and back hems. Chains must be named consistently (e.g., coat_hem_L_01, coat_hem_L_02) so they can be used with a Unity spring-bone or dynamic-bone solution. Do

not use Unity's Cloth component, which is too expensive for mobile.

Robotic arm pistons: each piston is modeled as two parts (cylinder and rod) driven by

Damped Track or Aim constraints (or an equivalent aim-based setup) between two anchor points, so the piston visibly extends and compresses as the arm moves. The freelancer must also deliver a Unity-compatible setup: either Unity

Animation Rigging (Multi-Aim/Aim constraints) on the exported rig or, if constraints cannot be exported, piston motion baked into the animations with a documented fallback. Constraint setups do not export through FBX, so the freelancer must explain which approach they use before starting.

• Hair (if long or loose): optional 1–2 bone chains for ponytail or strands, within budget.
• Skinning Quality Standards:
  • Maximum 4 bone influences per vertex (Unity mobile default), with weights normalized.
  • Smooth, artifact-free weight painting at shoulders, elbows, hips and knees. Rigid 100% weighting on mechanical arm parts.
  • Weights must be tested through the full range of motion, with no stretching, volume loss or vertex popping.
  • Total bone count under 90 (including secondary bones).

4. Facial Rigging & Blendshapes

Methodology: Blendshape-based facial setup using the

ARKit naming convention (reduced set for mobile). Joint-based jaw only if needed for the engine.

• Phonemes & Expressions:
  • Minimum required set (about 20 shapes): eyeBlinkLeft/Right, eyeWideLeft/Right, eyeLookUp/Down/In/OutLeft/Right (or an equivalent eye-direction setup), browDownLeft/Right, browInnerUp, browOuterUpLeft/Right, jawOpen, mouthSmileLeft/Right, mouthFrownLeft/Right, mouthFunnel, mouthPucker, cheekPuff.
  • Visemes for basic lip sync (A/E/I/O/U, M/B/P, F/V) can be generated from the ARKit shapes above.
  • Full 52-shape set: optional upgrade, quoted as a separate line item.
  • Eyes are separate meshes, and eyelids are blendshape-driven (no eyelid bones).

Corrective Shapes: Maximum 2–3 corrective shapes, only where the basic blendshapes visibly break (e.g., wide-open mouth combined with a smile). Blendshapes must be additive with no conflicting vertex movement, and each starts from the same neutral base mesh.

5. Deliverables & Acceptance Checklist

• Export Formats:
  • .fbx (Unity-ready, deform bones only, meshes and blendshapes embedded, textures not embedded).
  • Clean, organized .blend source file with the control rig and layered collections (mesh, rig, controls).
  • Textures as PNG (or TGA) in a separate folder with consistent naming.
  • Unity package or tested prefab (URP materials, Humanoid Avatar configured, piston and cloth bone setup working).
  • A short README documenting the bone naming, piston setup and how to run the cloth bones.
• Milestone Verification Steps:
  1.

Concept/model review: silhouette check in A-pose, triangle count verified at or below 35,000, clean topology (no n-gons) and UV layout.
2. Texturing review: materials (max 3) and texture sizes confirmed in Unity URP under mobile-like lighting.
3.

Rig review: Range-of-Motion (ROM) deformation test of all joints, IK/FK switching in Blender, weights with 4 influences max, twist bones working.
4.

Mechanics review: robotic piston motion working through arm movement, and coat hem bones moving correctly with spring-bone dynamics.
5.

Facial review: blendshape slider verification for all required shapes and a short test of dialogue-style lip movement.
6.

Engine import test: clean .fbx import into Unity with a valid Humanoid Avatar, correct scale, no joint zeroing or rotation errors, no extra root nodes, and an idle and run animation previewed in-engine.
7. Final payment release only after all six checks pass and the source files are delivered.

If you'd like, I can also write a shorter, post-ready version of this brief with a budget and timeline section for Upwork or Fiverr.