Highly complex and dense models of 3D objects have recently become indispensable in digital industries. Mesh decimation then plays a crucial role in the production pipeline to efficiently get visually convincing yet compact expressions of complex meshes. However, the current pipeline typically does not allow artists control the decimation process, just a simplification rate. Thus a preferred approach in production settings splits the process into a first pass of saliency detection highlighting areas of greater detail, and allowing artists to iterate until satisfied before simplifying the model. We propose a novel, efficient multi-scale method to compute mesh saliency at coarse and finer scales, based on fast mesh entropy of local surface measurements. Unlike previous approaches, we ensure a robust and straightforward calculation of mesh saliency even for densely tessellated models with millions of polygons. Moreover, we introduce a new adaptive subsampling and interpolation algorithm for saliency estimation. Our implementation achieves speedups of up to three orders of magnitude over prior approaches. Experimental results showcase its resilience to problem scenarios that efficiently scales up to process multi-million vertex meshes. Our evaluation with artists in the entertainment industry also demonstrates its applicability to real use-case scenarios.

Despite the popularity of three-dimensional (3D) animation techniques, the style of 2D cel animation is seeing increased use in games and interactive applications. However, conventional 3D toon shading frequently requires manual editing to clean up undesired shadows or add stylistic details based on art direction. This editing is impractical for the frame-by-frame editing in cartoon feature film post-production. For interactive stylised media and games, post-production is unavailable due to real-time constraints, so art-direction must be preserved automatically. For these reasons, artists often resort to mesh and texture edits to mitigate undesired shadows typical of toon shaders. Such edits allow real-time rendering but are limited in resolution, animation quality and lack detail control for stylised shadow design. In our framework, artists build a “shading rig,” a collection of these edits, that allows artists to animate toon shading. Artists pre-animate the shading rig under changing lighting, to dynamically preserve artistic intent in a live application, without manual intervention. We show our method preserves continuous motion and shape interpolation, with fewer keyframes than previous work. Our shading shape interpolation is computationally cheaper than state-of-the-art image interpolation techniques. We achieve these improvements while preserving vector quality rendering, without resorting either to high texture resolution or mesh density.

Motion capture is increasingly used in games and movies, but often requires editing before it can be used, for many reasons. The motion may need to be adjusted to correctly interact with virtual objects or to fix problems that result from mapping the motion to a character of a different size or, beyond such technical requirements, directors can request stylistic changes. Unfortunately, editing is laborious because of the low-level representation of the data. While existing motion editing methods accomplish modest changes, larger edits can require the artist to “re-animate” the motion by manually selecting a subset of the frames as keyframes. In this paper, we automatically find sets of frames to serve as keyframes for editing the motion. We formulate the problem of selecting an optimal set of keyframes as a shortest-path problem, and solve it efficiently using dynamic programming. We create a new simplified animation by interpolating the found keyframes using a naive curve fitting technique. Our algorithm can simplify motion capture to around 10% of the original number of frames while retaining most of its detail. By simplifying animation with our algorithm, we realize a new approach to motion editing and stylization founded on the time-tested keyframe interface. We present results that show our algorithm outperforms both research algorithms and a leading commercial tool.

We propose a method of three-dimensional (3D) modeling of volumetric fluid phenomena from sparse multi-view images (e.g., only a single-view input or a pair of front- and side-view inputs). The volume determined from such sparse inputs using previous methods appears blurry and unnatural with novel views; however, our method preserves the appearance of novel viewing angles by transferring the appearance information from input images to novel viewing angles. For appearance information, we use histograms of image intensities and steerable coefficients. We formulate the volume modeling as an energy minimization problem with statistical hard constraints, which is solved using an expectation maximization (EM)-like iterative algorithm. Our algorithm begins with a rough estimate of the initial volume modeled from the input images, followed by an iterative process whereby we first render the images of the current volume with novel viewing angles. Then, we modify the rendered images by transferring the appearance information from the input images, and we thereafter model the improved volume based on the modified images. We iterate these operations until the volume converges. We demonstrate our method successfully provides natural-looking volume sequences of fluids (i.e., fire, smoke, explosions, and a water splash) from sparse multi-view videos. To create production-ready fluid animations, we further propose a method of rendering and editing fluids using a commercially available fluid simulator.

The goal of a practical facial animation retargeting system is to reproduce the character of a source animation on a target face while providing room for additional creative control by the animator. This article presents a novel spacetime facial animation retargeting method for blendshape face models. Our approach starts from the basic principle that the source and target movements should be similar. By interpreting movement as the derivative of position with time, and adding suitable boundary conditions, we formulate the retargeting problem as a Poisson equation. Specified (e.g., neutral) expressions at the beginning and end of the animation as well as any user-specified constraints in the middle of the animation serve as boundary conditions. In addition, a model-specific prior is constructed to represent the plausible expression space of the target face during retargeting. A Bayesian formulation is then employed to produce target animation that is consistent with the source movements while satisfying the prior constraints. Since the preservation of temporal derivatives is the primary goal of the optimization, the retargeted motion preserves the rhythm and character of the source movement and is free of temporal jitter. More importantly, our approach provides spacetime editing for the popular blendshape representation of facial models, exhibiting smooth and controlled propagation of user edits across surrounding frames.

This paper presents a method for controlling simulated explosions by prediction and optimization. Many methods have been proposed for simulating realistic explosion based on numerical fluid analysis. These methods are widely used in applications such as movies and computer games. In these applications, there is often a requirement for the explosion to conform to a specified final shape. The goal of our research is to meet this requirement by controlling the simulation so that the explosion evolves into a target shape specified by the user. The key ideas of our method are optimization of the initial velocities at the explosion source and predictive control of the simulation. Our method optimizes the initial velocities during the preprocessing step. Next, during the simulation, it predicts the future shape from the history of the explosion shape and controls the simulation to minimize the difference between the target shape and the predicted shape.

Abstract We present a method for synthesizing fluid animation from a single image, using a fluid video database. The user inputs a target painting or photograph of a fluid scene along with its alpha matte that extracts the fluid region of interest in the scene. Our approach allows the user to generate a fluid animation from the input image and to enter a few additional commands about fluid orientation or speed. Employing the database of fluid examples, the core algorithm in our method then automatically assigns fluid videos for each part of the target image. Our method can therefore deal with various paintings and photographs of a river, waterfall, fire, and smoke. The resulting animations demonstrate that our method is more powerful and efficient than our prior work.

The goal of scattered data interpolation techniques is to construct a (typically smooth) function from a set of unorganized samples. These techniques have a wide range of applications in computer graphics. For instance they can be used to model a surface from a set of sparse samples, to reconstruct a BRDF from a set of measurements, to interpolate motion capture data, or to compute the physical properties of a fluid. This course will survey and compare scattered interpolation algorithms and describe their applications in computer graphics. Although the course is focused on applying these techniques, we will introduce some of the underlying mathematical theory and briefly mention numerical considerations.

The definition of "important" or salient points on a shape is an old and fundamental problem in computer graphics. Important points, which we will term key points, can be used for representing a shape (e.g. as vertices of a polyline or as knots of a spline). Key points that correspond to perceptually salient points are useful as handles for editing. Key points are also good points to retain in simplifying a shape.

Abstract 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.

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.

Abstract In the context of non‐photorealistic imaging, such as digital cel animation, lighting is symbolic and stylized to depict the scene's mood and the geometric or physical features of the objects in the scene. Stylized light and shade should therefore be intentionally animated rather than rigorously simulated. However, it is difficult to achieve smooth animation of light and shade that are stylized with a user's intention, because such stylization cannot be achieved using just conventional 3D lighting. To address this problem, we propose a 3D stylized lighting method, focusing on several stylized effects including straight lighting, edge lighting, and detail lighting which are important features in hand‐drawn cartoon animation. Our method is an extension of the conventional cartoon shader and introduces a light coordinate system for light shape control with smooth animations of light and shade. We also extend a toon mapping process for detailed feature lighting. Having these algorithms in a real‐time cartoon shader, our prototype system allows the interactive creation of stylized lighting animations. We show several animation results obtained by our method to illustrate usefulness and effectiveness of our method. 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.

Abstract We propose a set of algorithms to efficiently make speech animation for 3D cartoon characters. Our prototype system is based on blendshapes, a linear interpolation technique, which is widely used in facial animation practice. In our system, a few base target shapes of the character, prerecorded voice, and its transcription are required as input. We describe a simple technique that amplifies the target shapes from few inputs using a generic database of viseme mouth shapes. We also introduce additional lip‐synch editing parameters that allow designers to quickly tune the lip movements. Based on these, we implement our prototype system as a Maya plug‐in. The demonstration movies created with this system illustrate well the practicality of our approach. Copyright © 2008 John Wiley & Sons, Ltd.

Abstract We propose a simple framework for making elastic body animation with point constraints. In general, a physics‐based approach for constraint animation offers a variety of animations with physically correct realism, which are achieved by solving the equations of motion. However, in the digital animation industry, solving the equations of motion is an indirect path to creating more art‐directed animations that maintain a plausible realism. Our algorithms provide animators a practical way to make elastic body animation with plausible realism, while effectively using point‐constraints to offer directatorial control. The animation examples illustrate that our framework creates a wide variety of point‐constraint animations of elastic objects with greater directability than existing methods. Copyright © 2008 John Wiley & Sons, Ltd.

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 an intuitive, interactive modeling and rendering system for creating non-photorealistic hairstyle images. The main feature of our system lies in its user-friendly sketch interface that allows the user to generate his/her desired hairstyle simply by drawing a few free-form strokes on the 3D model of a scalp. Hairstyles are modeled with a polygon based technique called cluster polygons, and are rendered expressively to obtain non-photorealistic images similar to those found in hand-drawn animations and cartoons.

We present a new system for interactively modeling and rendering nonphotorealistic hairstyles. The system is featured with a user-friendly sketch interface allowing a user generate his/her desired hairstyle simply by drawing a few free-form strokes. Hairstyles are modeled with a new polygon based technique called cluster polygon, and can be rendered expressively to obtain hair images similar to those found in cell animation and cartoons.

In a cel animation workplace, nonphotorealistic rendering techniques are often applied to a 3D scene model, which is constructed by referring to the 2D hand-drawn images of the scene. There exist a lot of scene features that must be modeled from the 2D information. The accentuation effects are amongst the most important features in a hand-drawn scene. In this context, accentuation refers to adding hand-drawn shading of the scene. The specific region that an artist wishes the viewer to observe is drawn brighter than the other regions. A method is proposed for the extraction of the accentuation effects from a single 2D painted image of an animated scene. This method enables the automatic addition of the accentuation effects to each frame of the animation, observed from other viewpoints.

The author presents the digital techniques and know-how that have been motivated, created and tried out through our work for cel animation. The techniques focus on extracting three-dimensional characteristics from two-dimensional images of the scene to be animated, or on merging 2D and 3D animations. Several animation examples are also demonstrated to show our practical skills, such as those for camera projection mapping for 3D structuring the 2D drawing scenes, and implicit/explicit use of 3D CG techniques for visual effects.

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.

A new method called TIP (Tour Into the Picture) is presented for easily making animations from one 2D picture or photograph of a scene.In TIP, animation is created from the viewpoint of a camera which can be three-dimensionally "walked or flownthrough" the 2D picture or photograph.To make such animation, conventional computer vision techniques cannot be applied in the 3D modeling process for the scene, using only a single 2D image.Instead a spidery mesh is employed in our method to obtain a simple scene model from the 2D image of the scene using a graphical user interface.Animation is thus easily generated without the need of multiple 2D images.Unlike existing methods, our method is not intended to construct a precise 3D scene model.The scene model is rather simple, and not fully 3D-structured.The modeling process starts by specifying the vanishing point in the 2D image.The background in the scene model then consists of at most five rectangles, whereas hierarchical polygons are used as a model for each foreground object.Furthermore a virtual camera is moved around the 3D scene model, with the viewing angle being freely controlled.This process is easily and effectively performed using the spidery mesh interface.We have obtained a wide variety of animated scenes which demonstrate the efficiency of TIP.CR Cat e g o ri e s an d S ub j e c t De s c ri p t o rs : I.3.3 [Computer Graphics]: Picture/Image Generation -viewing algorithms; I.3.7 [Computer Graphics] Three-dimensional Graphics and Realism, Animation Addi ti o nal Key wo rds : graphical user interface, imagebased modeling/rendering, vanishing point, field-of-view angle

This paper describes the method for modeling human figure locomotions with emotions.Fourier expansions of experimental data of actual human behaviors serve as a basis from which the method can interpolate or extrapolate the human locomotions.This means, for instance, that transition from a walk to a run is smoothly and realistically performed by the method.Moreover an individual's character or mood, appearing during the human behaviors, is also extracted by the method.For example, the method gets "briskness" from the experimental data for a "normal" walk and a "brisk" walk.Then the "brisk" run is generated by the method, using another Fourier expansion of the measured data of running.The superposition of these human behaviors is shown as an efficient technique for generating rich variations of human locomotions.In addition, step-length, speed, and hip position during the locomotions are also modeled, and then interactively controlled to get a desired animation.

article Free Access Share on A simple method for extracting the natural beauty of hair Authors: Ken-ichi Anjyo Hitachi Research Lntmratory, 4026 Kuji, Hitachi, Ibaraki 319-12, Systems Engineering Division, IIitachi, Ltd., 4-6, Kanda-Surugadai, Chiyoda Tokyo 101 Hitachi Research Lntmratory, 4026 Kuji, Hitachi, Ibaraki 319-12, Systems Engineering Division, IIitachi, Ltd., 4-6, Kanda-Surugadai, Chiyoda Tokyo 101View Profile , Yoshiaki Usami Hitachi Research Lntmratory, 4026 Kuji, Hitachi, Ibaraki 319-12 Hitachi Research Lntmratory, 4026 Kuji, Hitachi, Ibaraki 319-12View Profile , Tsuneya Kurihara Hitachi Central Resenrch LAmratory, 1-280 Higashi-Koigakubo, Kokubunji, Tokyo 185 Hitachi Central Resenrch LAmratory, 1-280 Higashi-Koigakubo, Kokubunji, Tokyo 185View Profile Authors Info & Claims ACM SIGGRAPH Computer GraphicsVolume 26Issue 2July 1992 pp 111–120https://doi.org/10.1145/142920.134021Published:01 July 1992Publication History 139citation2,443DownloadsMetricsTotal Citations139Total Downloads2,443Last 12 Months159Last 6 weeks23 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

Semi-globalized spectral synthesis is proposed as a new tool for three-dimensional scene description consisting of many natural objects, such as terrain, sea waves, and clouds. The method is based on the mathematical theory of spectral representation of stochastic processes. In this paper, mathematical models in the method are presented under rigorous formulation and then their stochastic properties are shown. Some simple techniques for practical improvements of the original models in depicting scenes are also explained along with the examples obtained.

Stochastic modeling has been widely used in computer graphics to depict natural objects or phenomena. Various techniques are available, depending on what object is to be represented and what extent of realism to be achieved. This paper presents a simple approach to stochastic spectral synthesis for producing a large range of natural objects and scenes at low computational cost. By considering a wide class of power spectra, the method can provide twodimensional stochastic models for various objects, involving terrains, clouds and sea waves. Moreover, some functional operations and parameters for the models are introduced, which can make the models more flexible in describing a three-dimensional complex scene.