Physically-Based Interactive Bi-Scale Material Design

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Physically-Based Interactive Bi-Scale Material Design

Hongzhi Wu Julie Dorsey Holly Rushmeier

Computer Graphics Group, Yale University





Abstract

We present the first physically-based interactive system to facilitate

the appearance design at different scales consistently, through ma-

nipulations of both small-scale geometry and materials. The core of

our system is a novel reflectance filtering algorithm, which rapidly

computes the large-scale appearance from small-scale details, by

exploiting the low-rank s***ctures of the Bidirectional Visible Nor-

mal Distribution Function and pre-rotated BRDFs in the matrix for-

mulation of our rendering problem. Our algorithm is three orders of

magnitude faster than a ground-***th method. We demonstrate vari-

ous editing results of different small-scale geometry with analytical

and measured BRDFs. In addition, we show the applications of our

system to physical realization of appearance, as well as modeling

of real-world materials using very sparse measurements.

CR Categories: I.3.7 [Computer Graphics]: Three-Dimensional

Graphics and Realism—Color, shading, shadowing, and texture

Keywords: bi-scale, material editing, reflectance filtering, low-

rank matrix

ric threads that are visible on close view merge into a material de-

scribed by a single reflectance function when viewed from a dis-

tance. Physically speaking, the large-scale appearance is uniquely

determined by averaging the look of small-scale details [***neton

and Neyret 2011]. Therefore, it would be desirable to build an edit-

ing system for interactive appearance design at different scales, by

manipulating small-scale s***ctures. This could be useful in appli-

cations like building exterior design, where the user edits the looks

of a building at different view distances.

Existing interactive material editing systems (e.g. [Ben-Artzi et al.

2006; Pellacini and Lawrence 2007]) focus on adjusting material

appearance only at a single scale. On the other hand, previous

work [Westin et al. 1992; Gondek et al. 1994], which computes

realistic large-scale appearance by simulating light interactions in

small-scale details, is too slow to provide interactive feedback.

Although converting small-scale s***ctures to large-scale appear-

ance is essentially performing reflectance filtering, related tech-

niques [***neton and Neyret 2011] are not suitable for our purpose,

due to the lack of support for general geometry and materials [Han

et al. 2007], or costly computational overhead [Wu et al. 2009].

This paper presents, to our knowledge, the first physically-based in-

teractive bi-scale material editing system, which manipulates small-

scale geometry and Bidirectional Reflectance Distribution Func-

tions (BRDFs), to facilitate appearance design at two different

scales consistently. The user can freely change both small-scale ge-

ometry and materials, then our system quickly computes the large-

scale appearance to provide interactive visual feedback. As illus-

trated in Fig. 1, various small-scale edits can have dramatic effects

on appearance. We achieve an acceleration rate of over 5000:1,

when compared with a ground-***th method similar to [Westin et al.

1992], implemented on modern hardware. The key to the per-

formance of our system is a novel reflectance filtering algorithm,

which efficiently processes the Bidirectional Visible Normal Dis-

tribution Function (BVNDF) and pre-rotated BRDFs, derived from

the changing small-scale details. We observe and exploit the low-

rank s***ctures in both quantities to accelerate the large-scale ap-

pearance computation, using Singular Value Decomposition (SVD)

combined with the random projection method [Vempala 2004].







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