NPR Shading & Look Development

Problem

During Cinev Studio development, we explored a shift from MetaHuman-based PBR to anime-style characters while keeping PBR environments. The two looks needed to work together. Even textures connected to Emissive appeared duller than intended, making the desired bright character look difficult to achieve.

Solution

When reference implementations were limited, I followed practitioners and developers and tested their approaches. I combined SDF face shadows, outlines, Matcap, and environment controls to develop the NPR prototype into looks used in the product.

I configured four base materials for different character types. In-house Toon and VRM Toon use Custom Depth and Post Process, while Zo Toon uses Emissive shading and Inverted Hull outlines for characters that combine PBR and NPR parts. SDF face shadows and dot-product-based two-tone shading provided the foundation for look development.

The turning point for a brighter character look

The turning point was compensating for Filmic Tone Mapping with FilmToneMapInverse at the material stage. Precompensating colors for subsequent tone mapping established a basis for the bright Japanese anime look I was targeting. I combined this with SDF face shadows and environment controls to adapt the look to automated lighting.

Decision: when shading conflicts with the intended mood

With AI controlling cameras and lighting, backlighting in a bright scene could make a character look more threatening than intended. I changed that treatment from two-tone shadows to environment-driven color tones. The decision came from evaluating how the rendered result served the scene’s intended mood.

Result

4 Base Materials

In-house and VRM have different material structures, and even within VRM, realistic and non-realistic parts are mixed. So four separate base materials were created.

4 base materials

1. In-house Toon

Dedicated toon material for in-house characters. On top of a structure that separates characters via Custom Depth buffer and renders them in NPR style through Post Process, I developed and maintained features such as SDF face shadow and Matcap reflection.

Global Shadow OFF / ON toggle demo

SDF Face Shadow

Standard NdotL produces unintuitive shadows around the nose and eye sockets. By controlling shadow boundaries with pre-baked distance information in SDF textures, face shadows fall naturally even as the lighting angle changes.

SDF face shadow lighting demo

SDF Shadow Mask texture

SDF texture sample → Light Direction dot → shadow mask output

Matcap Reflection

PBR reflections don't suit NPR environments. I used Matcap textures for view-based reflections on hair highlights, skin sheen, etc. Turned out it could fake rim lighting too, so I built Matcap Painter to make those textures faster.

Matcap reflection demo

2. VRM Toon

Restructured parameter input names based on the in-house toon material to conform to MToon conventions. Ensured MToon textures and flags are automatically connected upon VRM import. Outline uses the same Post Process approach as the in-house material.

PP outline mask processing — unnecessary line removal + Material/Blueprint implementation

Angel Ring Matcap

Applied Matcap to the specular map to create a natural sheen effect that shifts with camera direction. Hair highlights like angel rings are achieved with a single ShadowSoft Matcap texture, and Matcap parameters are exposed on the material instance so the art team can easily adjust per-character look dev.

Angel Ring Matcap Before / After

Matcap_ShadowSoft parameter settings

3. VRM PBR

This material adapts VRM4U-based PBR shading for VRM characters. An SSS Profile adds volume to the skin for a bisque-doll-like finish, with the tone adjusted to sit alongside Toon characters and PBR environments.

4. VRM Zo Toon

The in-house post-process NPR approach made mixed PBR and NPR parts within one character difficult to handle. I developed a separate material using Emissive-based shading and inverted-hull outlines, matching its tone to the in-house characters.

Zo Toon material node graph — Emissive-based toon shading

Zo Toon(Inverted Hull) vs VRM Toon(Post Process) outline comparison

Zo Toon + PBR non-realistic/realistic combination showcase

PBR realistic part + Toon non-realistic part mixed result

Material	Base Pass	Samplers
In-house Toon	433 inst	7 / 16
VRM Toon	369 inst	4 / 16
Zo Toon	226 inst	3 / 16

Recorded Base Pass instruction counts: 433 → 226. This is a material statistic, not a GPU frame-time measurement.

UDS / ToD Integration Test

A nine-frame record comparing character and environment looks across lighting and Time of Day settings. I checked the results in scene context as well as under individual lighting setups.