A Simulation of Pearl Optical Phenomena
for Cosmetic Preproduction
Kensuke Tobitani∗
Kwansei Gakuin University1Akihiro Okada
Naris Cosmetics Co.,Ltd.
Lisa ParkKwansei Gakuin UniversityIntroduction

In the area of materials development, preproduction using visual simulation
has come to be considered essential. In this paper, we propose a simulationof pearl optical phenomena for cosmetic preproduction. Pearls manifest
a very specific optical phenomenon caused by their multilayered thin-film
structure, and most people have a common sense that pearls have a uniquebeauty. Therefore, the expected merits of the simulation for cosmetic preproduction are not negligible.

2Computational Model of A Pearl based on
Physics

The co-authors of this research succeeded in achieving a realistic representation of a pearl by means of three principal factors, namely, the interferencecomponent, mirroring component, and texture component, using physicsbased modeling (called an “illuminant model”) [Nagata et al. 1997]. Furthermore, Dobashi et al. indicated the importance of the blurring of light,
as a fourth factor, to improve the representation of a delicate appearance,and proposed its computational model and calculation algorithm. In thesestudies, they succeeded in a generating high-quality perfect sphere pearl
CG image which consists of four components: interference of incoherent
light, blurring, diffusion and interference of coherent light components. Itis, however, necessary to apply the visualizing method to a free-form surface
for our purpose.

3Expansion of Blurring Model

3.1

BRDF simulation using Monte Carlo method

The pearl visual simulation method described in Section 2 utilized the CookTorrance reflection model to represent the blurring of a pearl. In this research, we simulate the BRDF of a pearl using the Monte Carlo method formore detailed representation of the blurring. Figure 1(a) shows a simulation
result which represents transition of the BRDF by changing the incident angle at intervals of 10 degrees. As shown in Figure 1(a), the asymmetricity
shifts left side to right side of the distribution with increase the incident
angle, and the BRDF finally has a large peak value from the influence ofKumiko Nishiyama
Atsushi Ishida
Naris Cosmetics Co.,Ltd.
Kwansei Gakuin University
Noriko Nagata
Kwansei Gakuin UniversityFresnel reflection. We measured the BRDF of the underside of a pearl oyster shell as shown in Figure 1(b). Although the pearl shell was not a perfectly flat surface, the measured BRDF indicates a similar tendency of theBRDF simulation. Therefore, it is reasonable to support that the blurring
phenomenon is properly simulated by the method.

3.2 Generation of free-form surface and 3D face model
CG Image
We implement the BRDF as look-up table in a plug-in material shader ofthe 3DCG software MAYA to apply the blurring model to a free-form surface and generate 3D images of the free-form surface and face model applied pearl optical phenomena. Figure 2 shows the synthesized free-form
surface image with diffusion, interference of incoherent light, blurring, andinterference of the coherent light component images. Figure 3 shows thesynthesized 3D face model.

(a) Diﬀuse component(b) Blurring and mirroring
component(c) Incoherent lightinterference component(d) Coherent lightinterference component(e) Synthesized image

Figure 2: Synthesized free-form surface with four components.

Figure 3: Synthesized face image.

4 Conclusion
1,000,000 trials per an insident angle

200,000

1.0
0°
10°
20°
30°
40°
50°
60°
70°
80°
90°

160,000

Number of samples

140,000
120,000
100,000

0°
10°
20°
30°
40°
50°
60°
70°

0.8

Relative reﬂectance

180,000

For cosmetic preproduction, we simulated pearl optical phenomena on afree-form surface by expansion of the blurring model, and confirmed that
this simulation was successful In the future, we plan to introduce naturalfluctuations and irregularities to build a model much closer to the actualphenomena of a pearl.

Incident elevation angle

Incident elevation angle

80,0000.6

0.4

60,00040,0000.2

20,0000-50 -40 -30 -20 -100010203040506070

Outgoing elevation angle (°)(a) Transition of simulated BRDF

80

90010203040

5060

7080

90

Figure 1: Simulated BRDF and BRDF of pearl oyster shell.
∗ e-mail:tobitani@kwansei.ac.jp
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SIGGRAPH 2013, July 21 – 25, 2013, Anaheim, California.
2013 Copyright held by the Owner/Author.
ACM 978-1-4503-2261-4/13/07
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References

Outgoing elevation angle (°)(b) BRDF of pearl oyster shell

NAGATA , N., D OBASHI , T., M ANABE , Y., U SAMI , T., AND I NOKUCHI ,S. 1997. Modeling and visualization for a pearl-quality evaluation simulator. Visualization and Computer Graphics, IEEE Transactions on 3,4 (oct-dec), 307 –315.