Human figures have been animated using a variety of geometric models including stick figures, polygonal models, and NURBS-based models with muscles, flexible skin, or clothing. This paper reports on experimental results indicating that a viewer’s perception of motion characteristics is affected by the geometric model used for rendering. Subjects were shown a series of paired motion sequences and asked if the two motions in each pair were the same or different. The motion sequences in each pair were rendered using the same geometric model. For the three types of motion variation tested, sensitivity scores indicate that subjects were better able to observe changes with the polygonal model than they were with the stick figure model.

Abstract. Altering the viewing parameters of a 3D object results in computergraphics images of varying quality. One aspect of image quality is the composition of the image. While the esthetic properties of an image are subjective, someheuristics used by artists to create images can be approximated quantitatively. We present an algorithm based on heuristic compositional rules for finding the for-mat, viewpoint, and layout for an image of a 3D object. Our system computes viewing parameters automatically or allows a user to explicitly manipulate them.

Placing shadows is difficult task since shadows depend on the relative positions of lights and objects in an unintuitive manner. To simplify the task of the modeler, we present a user interface for designing shadows in 3d environments. In our interface, shadows are treated as first-class modeling primitives just like objects and lights. To transform a shadow, the user can simply move, rescale or rotate the shadow as if it was a 2d object on the scene’s surfaces. When the user transforms a shadow, the system moves lights or objects in the scene as required and updates the shadows in realtime during mouse movement. To facilitate interaction, the user can also specify constraints that the shadows must obey, such as never casting a shadow on the face of a character. These constraints are then verified in real-time, limiting mouse movement when necessary. We also integrate in our interface fake shadows typically used in computer animation. This allows the user to draw shadowed and non-shadowed regions directly on surfaces in the scene.

We present a framework for interactive lighting design based on linear re-rendering. The rendering operation is linear with respect to light sources, assuming a fixed scene and camera geometry. This linearity means that a scene may be interactively rerendered via linear combination of a set of basis images, each rendered under a particular basis light.We focus on choosing and designing a suitable set of basis lights. We provide examples of bases that allow 1) interactive adjustment of a spotlight direction, 2) interactive adjustment of the position of an area light, and 3) a combination in whichlight sources are adjusted in both position and direction. We discuss a method for reducing the size of the basis using principal components analysis in the image domain.

Specifying parameters of analytic BRDF models is a difficult task as these parameters are often not intuitive for artists and their effect on appearance can be non-uniform. Ideally, a given step in the parameter space should produce a predictable and perceptually-uniform change in the rendered image. Systems that employ psychophysics have produced important advances in this direction; however, the requirement of user studies limits scalability of these approaches. In this work, we propose a new and intuitive method for designing material appearance. First, we define a computational metric between BRDFs that is based on rendered images of a scene under natural illumination.

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direct indirect paint-all paint-one lighting lighting lighting painting lighting painting 225- s: key refinement 215- s: key refinement 240- s: lighting features 285- s: adjustments 160-225 s: fill light 190-215 s: fill light 135-240 s: intensity 140-265 s: key intensity 75-160 s: key light 155-175 s: key light 0-70 s: background 65-140 s: key hotspot Figure 1: Example workflow of a novice subject lighting a simple scene with one key and one fill light using four different lighting interfaces.

shaped halls bring the audience closer to the stag e than other configBCSq;BCD but they may fail to make the listener feel surrounded by the sound. The application ofhig( y absorbent materials may reducedisturbing echoes, but they may also deaden the hall. In many renovations,budg etary, aesthetic, or physical impediments limit modifications, compounding the difficultiesconfronting thedesig(3 . In addition, a hall migq need to accommodate a widerang e of performances, from lectures to symphonic music, each with different acoustic requirements. In short, a concert hall's acoustics depends on thedesigCS 's ability to balance many factors. Here, we present an inverse, interactive acoustic desig approach that helps adesig(q produce an architecturalconfigqC: CVD that achieves a desired acoustic performance. For a newbuilding the system maysug g est optimalconfig3BB:q;0 that would not otherwise be considered; for a hall with modifiable components or for a renovation project, it may assist in

Figure 1: Traditional computer graphics algorithms produce “accurate ” shadows (left). Artists often deliberately render abstract shadows, such as the shadow with reduced contour detail in this painting by Vanderlyn, 1818 (middle). Our system offers controls for creation of stylized shadows (right). While much research has focused on rendering physically-correct shadows, a “correct ” shadow often exhibits unnecessary detail that distracts from the primary subject of the scene. Artists often prefer to have creative control over the rendered appearance of the shadow. This paper presents an algorithm offering control over stylized shadows, based on four intuitive parameters – inflation, brightness, softness, and abstraction – that together support a broad range of effects. The algorithm, which works largely in image space, can easily be incorporated into existing rendering pipelines, and is independent of scene geometry or shadow determination method. 1

We present a new framework for rendering virtual environments. This framework is proposed as a complete scene description, which embodies the space of all possible renderings, under all possible lighting scenarios of the given scene. In effect, this hypothetical rendering space includes all possible light sources as part of the geometric model. While it would be impractical to implement the general framework, this approach does allow us to look at the rendering problem in a new way. Thus, we propose new representations that are subspaces of the entire rendering space. Some of these subspaces are computationally tractable and may be carefully chosen to serve a particular application. The approach is useful both for real and virtual scenes. The framework includes methods for rendering environments which are illuminated by artificial light, natural light, or a combination of the two models. 1 Introduction The emerging field of visualization in computer science combines calculations with c...