Ken-ichi Anjyo

A simple method for extracting the natural beauty of hair

A simple differential equation method is proposed for modeling the aesthetic features of human hair. In the method, a simplified cantilever beam simulation is employed for hairstyle modeling, which allows hairdressing variations with volumetric and realistic appearance. In order to describe the dynamical behavior of hair in an animation, one-dimensional projective differential equations of angular momenta for linked rigid sticks are also derived. For the problem of collision detection between hair and a human head, the “rough” approximate solution is provided, which gives visually satisfactory results by solving the projective equations under a ps~udo-force field. The hair’s pliability can be controlled by using a set of stiffness parameters in the method. In addition, a fast rendering technique for anisotropic reflection is introduced, which is derived from Blirm’s specular model. The efficiency of the proposed method is illustrated by the still images and short animations obtained. CR

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.

Tour Into the Picture using a Vanishing Line and its Extension to Panoramic Images

Tour into the picture (TIP) proposed by Horry et al.13 is a method for generating a sequence of walk‐through images from a single reference picture (or image). By navigating a 3D scene model constructed from the picture, TIP produces convincing 3D effects. Assuming that the picture has one vanishing point, they proposed the scene modeling scheme called spidery mesh. However, this scheme has to go through major modification when the picture contains multiple vanishing points or does not have any well‐defined vanishing point. Moreover, the spidery mesh is hard to generalize for other types of images such as panoramic images. In this paper, we propose a new scheme for TIP which is based on a single vanishing line instead of a vanishing point. Based on projective geometry, our scheme is simple and yet general enough to address the problems faced with the previous method. We also show that our scheme can be naturally extended to a panoramic image.

Tweakable light and shade for cartoon animation

Light and shade in the context of non-photorealistic imaging, such as digital cel animation, are semantic notations, rather than physical phenomena. Therefore stylized light and shade should be intentionally animated instead of simulated. This paper proposes an intuitive, direct manipulation method for animating stylized light and shade in real-time. Our method provides intuitive click-and-drag operations for translating and deforming the shaded areas, including rotation, directional scaling, splitting, and squaring of high-lights, all without tedious parameter tuning. Our prototype system demonstrates the algorithms in our method, which are implemented along with a real-time cartoon shader on commodity graphics hard-ware. This system allows the interactive creation of stylized shading keyframes for animations, illustrating the effectiveness of the proposed techniques.

Hair animation with collision detection

We propose an efficient method for hair animation. The movement of hairs is modeled by simplified physical simulations. In particular the method can treat successfully collisions between hair and a human body or other objects, which provides realistic hair animation. The fast collision detection is achieved using cylindrical representation of the head and human body parts, despite a large number of hairs. The cylindrical representation allows collision detection to be performed by table look-up and interpolation, which assures that the computation time is independent of the complexity of the objects. A reaction constraint algorithm is also applied for the collision reaction to simulate inelastic contact. The efficiency of the method is well illustrated by the animation obtained.

Rigid shape interpolation using normal equations

In this paper we provide a new compact formulation of rigid shape interpolation in terms of normal equations, and propose several enhancements to previous techniques. Specifically, we propose 1) a way to improve mesh independence, making the interpolation result less influenced by variations in tessellation, 2) a faster way to make the interpolation symmetric, and 3) simple modifications to enable controllable interpolation. Finally we also identify 4) a failure mode related to large rotations that is easily triggered in practical use, and we present a solution for this as well.

Bilinear interpolation for facial expression and metamorphosis in real-time animation

This paper describes a new method for generating facial animation in which facial expression and shape can be changed simultaneously in real time. A 2D parameter space independent of facial shape is defined, on which facial expressions are superimposed so that the expressions can be applied to various facial shapes. A facial model is transformed by a bilinear interpolation, which enables a rapid change in facial expression with metamorphosis. The practical efficiency of this method has been demonstrated by a real-time animation system based on this method in live theater.

Latent Doodle Space

We propose the concept of a latent doodle space, a low‐dimensional space derived from a set of input doodles, or simple line drawings. The latent space provides a foundation for generating new drawings that are similar, but not identical to, the input examples. The two key components of this technique are 1) a heuristic algorithm for finding stroke correspondences between the drawings, and 2) the use of latent variable methods to automatically extract a low‐dimensional latent doodle space from the inputs. We present two practical applications that demonstrate the utility of this idea: first, a randomized stamp tool that creates a different image on every usage; and second, “personalized probabilistic fonts,” a handwriting synthesis technique that mimics the idiosyncrasies of ones own handwriting.

Animating Pictures of Fluid using Video Examples

We propose a system that allows the user to design a continuous flow animation starting from a still fluid image. The basic idea is to apply the fluid motion extracted from a video example to the target image. The system first decomposes the video example into three components, an average image, a flow field and residuals. The user then specifies equivalent information over the target image. The user manually paints the rough flow field, and the system automatically refines it using the estimated gradients of the target image. The user semi‐automatically transfers the residuals onto the target image. The system then approximates the average image and synthesizes an animation on the target image by adding the transferred residuals and warping them according to the user‐specified flow field. Finally, the system adjusts the appearance of the resulting animation by applying histogram matching. We designed animations of various pictures, such as rivers, waterfalls, fires, and smoke.

A practical method of constructing surfaces in three-dimensional digitized space

We propose a new, practical algorithm for constructing the surface of a three-dimensional object from its planar cross-sections. This algorithm deals with a general case where each cross-section of the object is given as a two-dimensional digital image and no topological information about these two adjacent cross-sections is assumed. In particular, it can handle the case where there are several connected components with some holes in each cross-section. The algorithms principle is derived from the “region growing” technique. which is well-known in two-dimensional image processing. By combining this algorithm with existing shading techniques, we can obtain a realistic image of a three-dimensional object.