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Workflow: Character Artist

Persona: Maya — only character artist at a 15-person studio shipping a fantasy RPG in Unity. 40+ unique NPC characters per project. Auto-rigging is the biggest time-saver.

What you'll build

End-to-end NPC character pipeline:

  1. Reference concept sheet (front/back/side views)
  2. 3D mesh from the concept sheet (image-to-3D)
  3. Auto-rig with humanoid skeleton
  4. Idle and walk animation preview
  5. Mocap extraction from a reference video

Prerequisites

pip install "assgen[inference]"
assgen server status   # confirm CUDA device is visible

Step 1 — Concept reference sheet

A front/back/side reference sheet gives the image-to-3D model the geometry cues it needs. Do not skip this — text-to-3D for bipedal characters is unreliable.

assgen gen visual concept generate \
  --prompt "elf ranger NPC, full body character sheet, front back side views, white background, clean line art, fantasy RPG style" \
  --wait

Review the output. Check:

  • Limbs are symmetric and clearly separated from the body in all views
  • No overlapping silhouettes between front and side

If unsatisfied, tweak the prompt and regenerate (takes ~1 minute).

Step 2 — Image-to-3D mesh

assgen gen visual model create \
  --input concept_<id>.png \
  --wait

When to use --prompt vs --input

--input (image-to-3D) almost always produces better results for characters. TripoSR is trained on object images — give it one. Text-only --prompt works for simple props but not bipedal characters.

Output: model_<id>.glb

Quick mesh quality check before rigging:

# Open in any GLB viewer (e.g. gltf.report) and look for:
# - Watertight mesh (no holes at wrists, ankles, neck)
# - Reasonable poly count (< 50k for game NPC)
# - No inverted normals (shading should be smooth)

Mesh is not clean enough for UniRig?

Import into Blender (free), run Mesh → Clean Up → Fill Holes, export back to .glb, then retry the rig step. UniRig fails loudly if the mesh has holes — you'll see a clear error message, not a silent 500.

Step 3 — Auto-rig

assgen gen visual rig auto \
  --input model_<id>.glb \
  --skeleton humanoid \
  --wait

The --skeleton humanoid flag tells UniRig to output a biped rig that maps to Unity's Humanoid avatar definition — required for Mecanim and any retargetable animation clip.

Output: rig_<id>.glb — mesh + skeleton + skin weights.

Rig quality checklist:

Check How
Spine chain is single, vertical Open in Blender → Armature → Bones
Finger count matches mesh Count bones in hand chain
Skin weights paint smoothly Object Mode → Weight Paint

Step 4 — Keyframe animation preview

What this step produces

visual.animate.keyframe uses AnimateDiff to render a video preview of the motion — it is not a retargetable BVH or FBX animation clip. Use it to validate the rig looks plausible before investing in mocap or hand-keyed animation.

assgen gen visual animate keyframe \
  --input rig_<id>.glb \
  --prompt "looping idle animation, breathing, weight shift, natural" \
  --wait

Output: animate_<id>.mp4 — a short preview video.

To get actual keyframe animation data for Unity, use the mocap step below or a dedicated animation tool like Cascadeur or Mixamo.

Step 5 — Mocap from reference video

If you have a short reference video of the motion you want:

assgen gen visual animate mocap \
  --input reference_walk.mp4 \
  --wait

Output: mocap_<id>.bvh — a BVH motion file.

Import BVH into Unity:

  1. Import the .bvh via the Unity Package Manager BVH importer, or use the BVH Importer asset from the Unity Asset Store (free)
  2. Set Rig → Animation Type → Humanoid and map to the assgen-generated skeleton
  3. Drag animation clips onto your Animator Controller

Full pipeline script

#!/bin/bash
set -e
CHARACTER="elf ranger NPC, fantasy RPG"

echo "→ Generating concept sheet..."
CONCEPT=$(assgen gen visual concept generate \
  --prompt "$CHARACTER, full body, front back side views, white background" \
  --wait --output-dir ./output | grep "output:" | awk '{print $2}')

echo "→ Creating 3D mesh from concept..."
MESH=$(assgen gen visual model create --input "$CONCEPT" --wait \
  --output-dir ./output | grep "output:" | awk '{print $2}')

echo "→ Auto-rigging (humanoid)..."
RIG=$(assgen gen visual rig auto --input "$MESH" --skeleton humanoid --wait \
  --output-dir ./output | grep "output:" | awk '{print $2}')

echo "→ Preview animation..."
assgen gen visual animate keyframe \
  --input "$RIG" --prompt "looping idle, breathing" --wait

echo "✓ Done: $RIG"

Unity export checklist

Before handing off to engineering:

  • [ ] Mesh is < 50k triangles (use Blender Decimate modifier if over)
  • [ ] Single UV island per mesh (no overlaps)
  • [ ] Skeleton uses Humanoid mapping (--skeleton humanoid ✓)
  • [ ] Textures are power-of-two resolution (512, 1024, 2048)
  • [ ] .glb file is < 50 MB

Known limitations

Gap Status Workaround
Text-to-motion (BVH from text prompt) No open model available (2026-03) Use Mixamo for standard motions, mocap for custom
Animation retargeting Manual Blender's Rigify retarget or Unity Humanoid avatar
Facial rigging Not in catalog Manual in Blender; ARKit blendshapes not yet supported

Next steps