Abstract We present a novel approach to the creation of varied animations from a small set of simple 2D input shapes. Instead of providing a new 2D shape for each keyframe of an animation sequence, we interpolate between a few example shapes in a reduced pose‐space. Similar approaches have been presented in the past, but were restricted in the types of input or range of deformations allowed. In order to address these limitations, we reformulate the problem as an N‐way morphing process on 2D input bitmap or vector graphics. Our formulation includes an N‐way mapping technique, an efficient, rigidity preserving nonlinear blending function, improved extrapolation and a novel scattered data interpolation technique to manage the reduced pose‐space. The resulting animations are correlated to paths in the reduced pose‐space, allowing users to intuitively and interactively control temporal behaviours with simple gestures. We demonstrate our techniques in several example animations. Copyright © 2009 John Wiley & Sons, Ltd.

We present new algorithms for the compatible embedding of 2D shapes. Such embeddings offer a convenient way to interpolate shapes having complex, detailed features. Compared to existing techniques, our approach requires less user input, and is faster, more robust, and simpler to implement, making it ideal for interactive use in practical applications. Our new approach consists of three parts. First, our boundary matching algorithm locates salient features using the perceptually motivated principles of scale-space and uses these as automatic correspondences to guide an elastic curve matching algorithm. Second, we simplify boundaries while maintaining their parametric correspondence and the embedding of the original shapes. Finally, we extend the mapping to shapes' interiors via a new compatible triangulation algorithm. The combination of our algorithms allows us to demonstrate 2D shape interpolation with instant feedback. The proposed algorithms exhibit a combination of simplicity, speed, and accuracy that has not been achieved in previous work.

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.

Abstract 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 one's own handwriting. Keywords: sketch, by‐example, style learning, scattered data interpolation, principal component analysis, radial basis functions, Gaussian processes, digital in‐betweening, handwriting synthesis

We present a flexible modeling approach capable of realistically simulating many varieties of brushes commonly used in painting. Our geometric model of brush heads is a combination of subdivision surfaces and hundreds of individual bristles represented by thin polygonal strips. We exploit bristle-to-bristle coherence, simulating only a fraction of the bristles and using interpolation for the remainder. Our dynamic model incorporates realistic physically-based deformation, including anisotropic friction, brush plasticity, and tip spreading. We use an energy minimization framework with a novel geometric representation of the brush head to generate a wider variety of brushes. Finally, we have developed an improved haptic model that provides realistic force feedback, directly related to the results of the brush dynamic simulation. Using this model, we are able to simulate a wide range of brush styles and create an excellent variety of strokes such as the crisp, curvy strokes of Western decorative painting, or rough scratchy strokes like certain Oriental calligraphy. We have also developed an exporter for a popular free 3D modeling package that makes it easier for non-programmers to create any desired style of brush, real or fanciful.

Abstract We present a viscous paint model for use in an interactive painting system based on the well‐known Stokes' equations for viscous flow. Our method is, to our knowledge, the first unconditionally stable numerical method that treats viscous fluid with a free surface boundary. We have also developed a real‐time implementation of the Kubelka‐Munk reflectance model for pigment mixing, compositing and rendering entirely on graphics hardware, using programmable fragment shading capabilities. We have integrated our paint model with a prototype painting system, which demonstrates the model's effectiveness in rendering viscous paint and capturing a thick,impasto‐like style of painting. Several users have tested our prototype system and were able to start creating original art work in an intuitive manner not possible with the existing techniques in commercial systems. Copyright © 2004 John Wiley & Sons, Ltd.

We present a survey of our recent research on the development of haptic interfaces for simulating creative processes with digital media, including 3D multiresolution modeling and 2D and 3D painting. We discuss the design issues involved and lessons learned. Based on the preliminary user studies, we observe that haptic interfaces can improve the level of usability of digital design systems and assist in capturing the feel of creative processes.

We present an algorithm and a system for accelerated display of massive static and dynamic environments using hierarchical simplification. Given a geometric dataset, we represent it using a scene graph and compute levels of detail (LODs) for each node in the graph. We augment the LODs with automatically-generated hierarchical levels of detail (HLODs) that serve as higher fidelity drastic simplifications of entire branches of the scene graph. We extend the algorithm to handle a class of dynamic environments by incrementally recomputing a subset of the HLODs on the fly when objects move. We leverage the properties of the HLOD scene graph in our system, using them to render the environment in a specified image quality or target frame rate mode. The resulting algorithms have been implemented as part of a system named SHAPE. We demonstrate its performance on complex CAD environments composed of tens of millions of polygons. Overall, SHAPE is able to achieve considerable speedups in frame rate with little loss in image quality.

We present a novel painting system with an intuitive haptic interface, which serves as an expressive vehicle for interactively creating painterly works. We introduce a deformable, 3D brush model, which gives the user natural control of complex brush strokes. The force feedback enhances the sense of realism and provides tactile cues that enable the user to better manipulate the paint brush. We have also developed a bidirectional, two-layer paint model that, combined with a palette interface, enables easy loading of complex blends onto our 3D virtual brushes to generate interesting paint effects on the canvas. The resulting system, DAB, provides the user with an artistic setting, which is conceptually equivalent to a real-world painting environment. Several users have tested DAB and were able to start creating original art work within minutes.