Micro-geometric Modeling of Human Face Skis for Cosmetic Analysis

彬彬

1 Introduction

Condition of skin is an important factor for the impression of faces.

Well-cared skins give shiny and beautiful impression, while dry and

rough skins loss the gloss and therefore they are less attractive.

These differences often attribute to the difference of their microgeometry.

Such micro-geometry of human skins consists of furrows

forming a mesh, ridges surrounded by the furrows, and pores.

Many of pores exist at intersections between furrows. We observed

that widths of pores are approximately proportional to their depths.

Most of existing works on impression analysis of human skins are

based on images of real photographs. However, this approach is

often very expensive: we need to ask many people to take photographs

of their skins to gather various conditions of skin images.

In contrast, we attempt to use images of computer-synthesized skins

for impression analysis of various conditions of skins while controlling

ridges, pores, and furrows independently. Human skin representation

is an important technique for entertainment movie production,

and skin modeling is therefore an active research topic.

This paper presents a technique for micro-geometry simulation of

human skins. The technique first generates pores forming a pattern

of a well-aligned triangular grid. It then divides the skin region by

applying the Delaunay triangulation algorithm to connect the pores.

It treats the triangles as ridges, and the edges as furrows. Finally,

the technique divides the pattern into a finer triangular mesh, so that

it can finely represent 3D geometry of pores, ridges, and furrows.

2 Geometric modeling of skin structure

We captured micro-geometry of real human skins to discuss and

design the modeling technique. We subjectively observed skins in

the following three conditions which are especially important for

cosmetics analysis:

[1: Well-cared skin] Furrows are continuous. Ridges are regularly

aligned, equally-sized, and roundly.

[2: Dry skin] Ridges are flat but regularly aligned. However, furrows

are so depthless that patterns are unclear.

[3: Pore-expanded skin] Pores are not only large but also deep.

Based on the above observation, we concluded that the following

parameters should be controllable while representing microgeometry

of skins:

Pore: radius, depth, and randomness of positions.

Ridge: heights, and randomness of heights.

Furrow: depths, widths, and directional dependency.

We aimed to develop a 3D modeling technique so that we can generate

various skins by freely controlling the above parameters. The

technique first generates patterns of pores, ridges, and furrows, applying

Delaunay triangular meshing. It then tessellates the patterns

into fine triangular polygons.

Figure 1(Upper-left) shows an illustration of processing flow of the

pattern generation, including generation of pores, ridges, and furrows.

The technique first generates a set of pores so that they form

a pattern of a well-aligned triangular grid. Here, it controls radii,

depths, and positions of pores based on the predefined parameters.

∗e-mailmihayu, mami, itot)@itolab.is.ocha.ac.jp

†e-mailnaruhito.toyoda, hiromi.sasamoto)@to.shiseido.co.jp

The technique then divides the skin region by applying the Delaunay

triangulation algorithm to connect the pores. It then treats

the triangles as ridges, and the edges as furrows, and controls their

shapes based on the parameters.

The technique then divides the pattern into a finer triangular mesh,

so that it can represent finer 3D geometry of pores, ridges, and furrows.

The technique first generates vertices of the triangular mesh.

It generates vertices inside pores on their centre and concentric circles.

It evenly generates vertices on the furrows. It also evenly

generates vertices inside the ridges, and assigns heights so that they

form a smoothly curved surface. Figure 1(Upper-left) shows an illustration

of the vertex generation. Finally, the technique generates

a finer triangular mesh by applying the Delaunay triangular mesh

to connect the vertices.

3 Examples and Future Work

Figure 1(Upper-right) shows an example simulating a well-cared

skin. In this example ridges and pores are regularly generated,

depths and widths of furrows are not direction-depend, and ridges

are plump and therefore look rich. Figure 1(Lower-left) shows an

example simulating a dry skin. In this example ridges are flat and

therefore relatively look poor. Figure 1(Lower-rihgt) shows an example

of a pore-expanded skin. This example also looks poor because

of randomness of sizes of pores. They demonstrate our technique

can simulate various skins by controlling the parameters.

We are dealig with the following issues as our on-going work: 1)

improvement of pattern generation considering directional dependency,

2) adjustment and reconsideration of parameters, 3) implementation

of polygon mapping technique onto the geometric models

of faces, and 4) integration with realistic rendering techniques.

tc

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