Hideki Todo

Locally controllable stylized shading

Recent progress in non-photorealistic rendering (NPR) has led to many stylized shading techniques that efficiently convey visual information about the objects depicted. Another crucial goal of NPR is to give artists simple and direct ways to express the abstract ideas born of their imaginations. In particular, the ability to add intentional, but often unrealistic, shading effects is indispensable for many applications. We propose a set of simple stylized shading algorithms that allow the user to freely add localized light and shade to a model in a manner that is consistent and seamlessly integrated with conventional lighting techniques. The algorithms provide an intuitive, direct manipulation method based on a paint-brush metaphor, to control and edit the light and shade locally as desired. Our prototype system demonstrates how our method can enhance both the quality and range of applicability of conventional stylized shading for offline animation and interactive applications.

A Practical Approach to Direct Manipulation Blendshapes

Abstract The original approach of direct manipulation blendshapes introduced a mathematical framework for manipulating blendshape face models directly and interactively while interoperating with traditional slider-based editing. This article introduces a few practical and useful techniques to the original work and presents the implementation details as a software tool. In addition, this article describes a statistical-prior algorithm that “learns” from previous animation and allows rapid creation of expressive animation in a given style. The animation examples illustrate how effectively this tool works for practical use.

Estimating reflectance and shape of objects from a single cartoon-shaded image

Although many photorealistic relighting methods provide a way to change the illumination of objects in a digital photograph, it is currently difficult to relight digital illustrations having a cartoon shading style. The main difference between photorealistic and cartoon shading styles is that cartoon shading is characterized by soft color quantization and nonlinear color variations that cause noticeable reconstruction errors under a physical reflectance assumption, such as Lambertian reflection. To handle this non-photorealistic shading property, we focus on shading analysis of the most fundamental cartoon shading technique. Based on the color map shading representation, we propose a simple method to determine the input shading as that of a smooth shape with a nonlinear reflectance property. We have conducted simple ground-truth evaluations to compare our results to those obtained by other approaches.

Digitization of natural objects with micro CT and photographs

In this paper, we present a three-dimensional (3D) digitization technique for natural objects, such as insects and plants. The key idea is to combine X-ray computed tomography (CT) and photographs to obtain both complicated 3D shapes and surface textures of target specimens. We measure a specimen by using an X-ray CT device and a digital camera to obtain a CT volumetric image (volume) and multiple photographs. We then reconstruct a 3D model by segmenting the CT volume and generate a texture by projecting the photographs onto the model. To achieve this reconstruction, we introduce a technique for estimating a camera position for each photograph. We also present techniques for merging multiple textures generated from multiple photographs and recovering missing texture areas caused by occlusion. We illustrate the feasibility of our 3D digitization technique by digitizing 3D textured models of insects and flowers. The combination of X-ray CT and a digital camera makes it possible to successfully digitize specimens with complicated 3D structures accurately and allows us to browse both surface colors and internal structures.

Textured splat based rendering for stylized shading

To create brush-stroke style animation with temporal coherence, the artist needs to refer the previous frame carefully for drawing. Moreover, brush-stroke lighting style is challenging to animate coherently because it dynamically changes and contains lots of features compared to physically-based lighting.

Inverse appearance modeling of interwoven cloth

This paper proposes an inverse approach for modeling the appearance of interwoven cloth. Creating the desired appearance in cloth is difficult because many factors, such as the type of thread and the weaving pattern, have to be considered. Design tools that enable the desired visual appearance of the cloth to be replicated are therefore beneficial for many computer graphics applications. In this paper, we focus on the design of the appearance of interwoven cloth whose reflectance properties are significantly affected by the weaving patterns. Although there are several systems that support editing of weaving patterns, they lack an inverse design tool that automatically determines the spatially varying bidirectional reflectance distribution function (BRDF) from the weaving patterns required to make the cloth display the desired appearance. We propose a method for computing the cloth BRDFs that can be used to display the desired image provided by the user. We formulate this problem as a cost minimization and solve it by computing the shortest path of a graph. We demonstrate the effectiveness of the method with several examples.

Measuring microstructures using confocal laser scanning microscopy for estimating surface roughness

Realistic image synthesis is an important research goal in computer graphics. One important factor to achieve this goal is a bidirectional reflectance distribution function (BRDF) that mainly governs an appearance of an object. Many BRDF models have therefore been developed. A physically-based BRDF based on microfacet theory [Cook and Torrance 1982] is widely used in many applications since it can produce highly realistic images. The microfacetbased BRDF consists of three terms; a Fresnel, a normal distribution, and a geometric functions. There are many analytical and approximate models for each of these terms.

Controllable region via texture projection for stylized shading

Existing texture projection methods are capable to produce irregular gradation shading, but still can not provide region control for acquiring artistic styles such as multiple lights effects and more detailed shading by painting. We improved the capability of light space normal notion from [Todo et al. 2013] by adjusting the z component so that region control can be achieved. Our approach effectively helps artist create smooth multiple lighting effects with additional painting control while keeping the high quality shading of the texture projection method..

Parametric stylized highlight for character animation based on 3D scene data

classroom use is granted without fee provided that copies are not made or distributed for commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for third-party components of this work must be honored. For all other uses, contact the Owner/Author. SIGGRAPH 2014, August 10 – 14, 2014, Vancouver, British Columbia, Canada. 2014 Copyright held by the Owner/Author. ACM 978-1-4503-2958-3/14/08 Parametric Stylized Highlight for Character Animation Based on 3D Scene Data

Practical region control in projective texture for stylized shading

Stylized shading in 3D rendering can boost the appeal of appearance and feeling to the viewer. In order to mimic stylized shading in artwork, much research focuses on remodelling illumination and texture functions.