Inking defines readable forms with controlled line weight. Automatic cel lines generate toon outlines and hard shadows from images or 3D renders. Mixamo retopo prepares meshes so Mixamo can auto-rig and your cel lines stay stable in motion. You’ll find quick decision trees, step-by-step pipelines, shader and preprocessor options, retopo rules for deformation, and troubleshooting for artifacts like jittering outlines or broken weights.

• 2D: Best for stills, manga panels, and short loops. Use AI line extractors and flat-color fills, then add cel shadows and outlines.
• 3D: Best for animation and consistent poses. Retopo → Mixamo auto-rig → toon shader + outline method → render passes.
• Hybrid: 3D base for pose/lighting + 2D inking pass for style cohesion. Useful for episodic content.

1. Source art: rough sketch, photo, or render.
2. Line extraction:

• Use a line preprocessor (e.g., lineart_anime, canny, softedge). Adjust thresholds to preserve primary contours and drop interior noise.
• Aim for closed shapes to simplify flats.

3. Clean inking:

• Thicken main silhouettes, taper internal detail. Use vector or high-res raster (≥300 DPI). Snap curves for mechanical elements.

4. Flats and cel shading:

• Auto-fill regions (segmentation/flood fills). Keep 3–5 tone levels. Use hard-edged shadows with a consistent light direction.

5. Final outlines:

• Optional Sobel/post-process pass for uniform stroke width.
• Add selective rim lines to separate character from background.

6. Upscale and denoise:

• Use detail-preserving upscalers. Avoid smoothing away line texture. Deliverables: clean line layer, flats, shadow layer, FX highlights, final composite.

1. Mesh prep and retopo:

• Create or import a character. Retopo to clean, even quads with loops around shoulders, elbows, hips, knees.
• Target 10k–40k quads for general animation; keep facial loops denser if needed.

2. UVs and export:

• Unwrap with minimal distortion; single UDIM if possible for simplicity.
• Freeze transforms, apply scale, correct normals.

3. Mixamo auto-rig:

• Export FBX/OBJ in T-pose or A-pose. Upload, place markers (chin, wrists, elbows, knees, groin), select skeleton type.
• Download rigged FBX with desired animation clips.

4. Toon shading and outlines (in DCC like Blender, Maya, or Unity/Unreal):

• Cel shader: ramp-based diffuse, 2–3 bands. Specular as a 1–2 step ramp.
• Outline methods:
  • Inverted hull: duplicate mesh, flip normals, push along normals, solid dark color.
  • Edge/Freestyle/NPR lines: view-dependent line sets by crease/silhouette.
  • Post-process: screen-space Sobel/normal-depth edge detection.

5. Render passes:

• Beauty (cel), shadow band, spec band, outline mask, Z/depth if compositing.

6. Composite:

• Balance outline thickness by screen size; add subtle halftone or paper grain if comic look is desired.

• Inverted hull (3D): controllable thickness, stable in motion; may need per-part offsets.
• Freestyle/NPR (3D): rich rule-based lines; more setup time.
• Screen-space edges (2D/3D): quick, uniform; can flicker on thin details.
• AI line extractors (2D): stylized, fast; requires careful thresholding to avoid chatter.
• Hybrid: 3D outline for silhouettes + 2D inking pass for internal accents.

• Even quads and clear loops at joints. Avoid long tris/ngons near elbows/shoulders/hips.
• Keep mouth/eyes with circular loops if facial motion matters.
• Aim for straight edge flows along limbs; minimize poles at bends.
• Thickness: avoid paper-thin surfaces; close open seams.
• Symmetry: apply before UVs; ensure clean centerline.
• Scale and pose: export neutral T/A-pose, Z-up or Y-up as your DCC needs; apply transforms.
• UVs: contiguous shells for limbs, consistent texel density; avoid extreme stretching (it affects toon ramps).
• Naming: simple mesh names; avoid non-ASCII characters.

Positive cues:

• "clean inking, bold contour lines, tapered strokes, cel-shaded, 2-tone shadows, anime lineart, hard-edged lighting, flat colors" Negative cues:
• "photoreal, soft focus, painterly blur, noisy edges, gradient mush" Control tips:
• Use lineart/softedge preprocessors to lock contours.
• Keep color palettes limited. Define a single light direction.
• If backgrounds are photoreal, add outline-only pass to characters for separation.

• Wobbly outlines in animation: increase pixel-thick outline methods (inverted hull over post-process), lock camera sampling, raise render samples slightly.
• Broken elbows/knees after Mixamo: retopo more loops at joints; reduce extreme bend angles; re-upload in a cleaner T-pose.
• Shading band banding too harsh: add one middle ramp step or slight dither; keep ramp textures in linear space.
• Line extractor chatter: raise threshold, pre-blur input slightly, simplify internal textures.
• Texture crawl: bake to UV-space, avoid procedural patterns that alias at distance.

• 2D: line layer (transparent), flats, shadow bands, spec band, FX, final composite at target DPI.
• 3D: rigged FBX, toon shader settings, outline method notes, render presets, pass breakdown.
• Assets: palettes, ramp textures, brushes, LUTs.
• Naming: project_scene_v###, character_v###, shader_ramp_v###.
• Documentation: light direction, outline thickness in pixels or world units.

• Line extraction: lineart_anime, canny, softedge, scribble preprocessors; vector tracing for final polish.
• DCC/Shaders: Blender (Toon BSDF + Freestyle/Inverted Hull), Maya (toon shader), Unity/URP, Unreal (post-process outlines).
• Retopo: Quad Remesher, Instant Meshes, Blender QuadriFlow, manual quad drawing.
• Rigging/Animation: Mixamo auto-rig + motion library; bake to keyframes for portability.
• Compositing: After Effects, Blender Compositor, Nuke; use depth/ID masks for selective outlines.