Figure 1: With the eight seeds (highlighted and shown in different colors) in a 64×64 grid on the leftmost picture, the progress of each round of the jump flooding algorithm is shown in the other six pictures, with the rightmost being the computed Voronoi diagram. This paper studies jump flooding as an algorithmic paradigm in the general purpose computation with GPU. As an example application of jump flooding, the paper discusses a constant time algorithm on GPU to compute an approximation to the Voronoi diagram of a given set of seeds in a 2D grid. The errors due to the differences between the approximation and the actual Voronoi diagram are hardly noticeable to the naked eye in all our experiments. The same approach can also compute in constant time an approximation to the distance transform of a set of seeds in a 2D grid. In practice, such constant time algorithm is useful to many interactive applications involving, for example, rendering and image processing. Besides the experimental evidences, this paper also confirms quantitatively the effectiveness of jump flooding by analyzing the occurrences of errors. The analysis is a showcase of insights to the jump flooding paradigm, and may be of independent interests to other applications of jump flooding.

Figure 1: Relief mapping of non-height-field surface details. Teapot with a weave pattern (left). Close-up views of the teapot’s body (center and right) reveal the back surface through the holes. Note the self-shadowing, occlusions and silhouettes. The ability to represent non-height-field mesostructure details is of great importance for rendering complex surface patterns, such as weave and multilayer structures. Currently, such representations are based on the use of 3D textures or large datasets of sampled data. While some of the 3D-texture-based approaches can achieve interactive performance, all these approaches require large amounts of memory. We present a technique for mapping non-height-field structures onto arbitrary polygonal models in real time, which has low memory requirements. It generalizes the notion of relief mapping to support multiple layers. This technique can be used to render realistic impostors of 3D objects that can be viewed from close proximity and from a wide angular range. Contrary to traditional impostors, these new one-polygon representations can be observed from both sides, producing correct parallax and views that are consistent with the observation of the 3D geometry they represent.

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Displacement mapping is a technique for applying fine geometric detail to a simpler base surface. The displacement is specified as a scalar function which makes it relatively easy to increase visual complexity without the difficulties inherent in more general modeling techniques. We would like to use displacement mapping in real-time applications. Ideally, a graphics accelerator should create a polygonal tessellation of the displaced surface on the fly to avoid storage and host bandwidth overheads. We present an online

We present a method relying on expansion textures to add details such as folds on a surface. The user paints the expansion attributes on the surface (amount and direction of expansion, wavelength and regularity of folds), using either interactive or procedural tools. The modeling system generates the folds by calculating the new surface equilibrium. Results show that this tool allows CG artists to easily control the aspect of folds and drapes by adding surface locally, which is close to the way sculptors think. Our original contribution does not lie in the equilibrium solver, but in the very principle of texturing expansions to specify shapes details.

This paper presents a method to simulate growth phenomena, and its application to the modeling of complex organic shapes (e.g., plants organs) and folded surfaces. Our main contribution is the interactive and stable resolution of the mechanical problem of growth-induced deformations, based on the minimization of the energy due to the various constraints in the shell. From this, we propose a new modeling approach based on a set of growing tools: The user can apply ’hot spots’, ’hot curves’, or paint growing parameters on the surface to grow. Growth can be simulated either simultaneously to the user interaction, or once all parameters have been settled on the surface (which allows the use of textures of parameters and procedural operations). The main parameters are the intensity and anisotropy of growth, as well as their variations over time. Geometric constraints and plasticity can also be considered. As our results show shapes can fold, bend, and curl as in nature, which deforming tools such as displacement map could not achieve. We demonstrate our tool with an interactive session and a gallery of shapes easily produced. 1. Introduction and Previous

This paper gives an overview of computer graphics representations of trees commonly used for the rendering of complex scene of vegetation. Looking for the right compromise between realism and efficiency has lead researchers to consider various types of geometrical plant models with different types of complexity. To achieve realist plant model, a complex structure of plant with full details is generally considered. In contrast, to promote efficiency, other approaches summarize plant geometry with few primitives allowing rapid rendering. Finally, to find a good compromise, structures with adaptive complexity are defined. Theses different types of representations and the ways to use them are presented, classified and discussed. The proposed classification principles rely on the type of structural details used in the plants representations. Characterization of all these methods is completed with various additional criteria including rendering primitive type, distance validity, interactive possibilities, animation ability and lighting properties.

Several techniques have been introduced to display meso-structure surface details to enhance the appearance of complex surfaces. One strategy is to avoid altogether costly semi-transparency in interactive contexts. However when dealing with hierarchical surface representations (important to filtering) and complex light transfers, semi-transparency must be treated. We propose a method that combines in a novel way multiple techniques from hardware rendering and volume visualization in order to render on current graphics hardware semitransparent meso-structure surface details stored in a 3D texture. The texture is mapped to an outer shell defined by tetrahedra extruded from the surface triangular mesh. The tetrahedra are first sorted on the CPU to be rendered in correct order. The attenuated color for each ray traversing each tetrahedron is efficiently computed with a hardware voxel traversal algorithm. The resulting structure is general enough to simulate at interactive rates from semitransparent surface details to opaque displacement maps, including several surface shading effects (visual masking, self-shadowing, absorption of light).

The simulation of complex layers of folds of cloth can be handled through algorithms which take the physical dynamics into account. In many cases, however, it is sufficient to generate wrinkles on a piece of garment which mostly appears spread out. This paper presents a corresponding fully GPU-based, easy-to-control, and robust method to generate and render plausible and detailed folds. This simulation is generated from an animated mesh. A relaxation step ensures that the behavior remains globally consistent. The resulting wrinkle field controls the lighting and distorts the texture in a way which closely simulates an actually deformed surface. No highly tessellated mesh is required to compute the position of the folds or to render them. Furthermore, the solution provides a 3D paint interface through which the user may bias the computation in such a way that folds already appear in the rest pose.

This paper introduces a technique for rendering animated grass in real time. The technique uses front-to-back compositing of implicitly defined grass slices in a fragment shader and therefore significantly reduces the overhead associated with common vegetation rendering systems. We also introduce a texture-based animation scheme that combines global wind movements with local turbulences. Since the technique is confined to a fragment shader, it can be easily integrated into any rendering system and used as a material in existing scenes.