Optimizing Highlight Effects in 3D Material Makeup Using Normal Maps

Background

3D material makeup relies on highlights to enhance the texture of the makeup; this paper proposes an optimization method that enables fine‑grained control of highlights to design aesthetically pleasing 3D makeup.

01 3D Material Makeup Introduction

Makeup technology is essentially computer graphics: it detects a face, computes a mesh, renders the mesh to obtain the makeup effect, and then blends the effect onto the face image. 3D makeup can be categorized into sticker makeup, custom makeup, and material makeup, with material makeup being widely used for its realism. Highlights are closely related to the visual quality of makeup.

Highlights are generated using virtual lighting models such as Phong, Physically Based Rendering (PBR), and Image‑Based Lighting (IBL). 3D material makeup has two main characteristics: strong light perception (highlight position, shape, and flow affect the final look) and strong visual appeal (aesthetic considerations may outweigh physical correctness).

02 Problem Description

Two face models (Model 1 and Model 2) extracted from different time frames of the same face have different geometric appearances but identical topology. Both use the same material and a directional light, rendered with a standard PBR model, resulting in noticeably different highlight positions and shapes due to geometry differences.

The goals are: (1) achieve consistent highlights across different faces under the same pose, and (2) make highlight position and shape controllable.

03 Problem Analysis

Analysis starts from the principle of highlight generation. Common lighting models (Phong, PBR, IBL) are discussed, with PBR being the most widely used. The PBR BRDF equation is presented, showing that metallic, roughness, base color, light direction, normal, and view vectors affect the final lighting.

Material parameters (metallic, roughness, base color) influence the intensity and color of highlights but not their position or shape. Light vector determines which region receives illumination but cannot adjust highlight shape. Geometry (normals) is identified as the key factor affecting highlight position and shape.

3.1 Lighting Model

Discussion of Phong, PBR, and IBL, emphasizing that PBR provides more physically accurate results and allows material definition via physical parameters.

3.2 Influence of Material Parameters

3.2.1 Metallic

Higher metallic reduces diffuse contribution, making highlights more pronounced. Images illustrate the effect of varying metallic values.

3.2.2 Roughness

Increasing roughness expands the highlight area. Images show the progression from small to large highlights.

3.2.3 Base Color

Base color changes the highlight hue. Red, green, and blue base colors produce corresponding highlight colors.

3.3 Influence of Light Vector

Directional light direction determines which facial region receives highlights but cannot modify highlight shape.

3.4 Influence of Geometry (Normals)

Experiments with two models of identical topology but different geometry show that using the same normal map on both yields nearly identical highlights, indicating normals are the dominant factor for highlight position and shape.

04 Highlight Optimization Scheme

Introduce a model‑space normal map into the rendering pipeline. By swapping or editing the normal map, designers can precisely control highlight position and shape while keeping material and lighting constant.

Applying different normal maps to the same model produces clearly different highlight patterns.

Thus, modifying the normal map alone can achieve any desired highlight effect.

05 Conclusion and Outlook

The paper identifies normals as the sole factor influencing highlight position and shape in 3D material makeup. By integrating a normal map into the rendering algorithm, both stability and controllability of highlights are achieved, enabling designers to create aesthetically pleasing makeup. Future work will further explore physically based material research for more realistic yet beautiful makeup effects.

References

[1] https://google.github.io/filament/Filament.html

[2] https://learnopengl-cn.github.io/

[3] https://www.pbr-book.org/

[4] https://blog.selfshadow.com/publications/s2013-shading-course/karis/s2013_pbs_epic_notes_v2.pdf