W. T. Reeves and R. Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. Computer Graphics, 19(3):313-322, July 1985.  Home/Search   Document Not in Database   Summary   Related Articles   Check

.... The basic building blocks of particle systems are well known and there are articles describing how one should build a real time particle system [Wit97] Lan98] McA00] Bur00] Particle systems are a popular tool for animation both in interactive graphics [Bur00] and in off line graphics [Ree85]. Thus most animation applications have direct support for particle systems (including Alias Wavefront Maya, LightWave and others) Wejchert has shown that it is important to use moving force fields when the aim is to create convincing animations [Wej91] Sims has given comprehensive overview of ....

.... Wejchert has shown that it is important to use moving force fields when the aim is to create convincing animations [Wej91] Sims has given comprehensive overview of the traditional particle systems [Sim90] Particle systems have been used to create flock behavior [Rey87] and structured systems [Ree85]. O Brien has shown a method for improving the performance of dynamics calculation [OBr01] by grouping particles to reduce the workload of force calculations. Particle systems are often used to create animations relying on fluid dynamics that can be modeled by using simplified versions of ....

Reeves W., Blau R., Approximate and probabilistic algorithms for shading and rendering structured particle systems, Approximate and probabilistic algorithms for shading and rendering structured particle systems, pages 313-322, 1985

....inhibition of growth due to several factors. Oppenheimer [Oppe86] took yet another approach (visually influenced by the work of Bloomenthal [Bloo85] using fractals to create tree models. His technique had the regrettable drawback of being limited to a small number of basic trees. Reeves and Blau [Reev85] developed a technique able of creating trees and grasses using a particle system. Recently, Benes and Millan [Bene02] presented an idea based on this work. It allows climbing plants to compete for space using oriented particles, which are able to sense the environment. Using directed random walks ....

Reeves W.T. and Blau R., Approximate and probabilistic Algorithms for Shading and Rendering Structured Particle Systems, SIGGRAPH ' 85, pp. 313-322, july 1985.

....rendering. Several modeling techniques were proposed to achieve realistic rendering. Models based on B ezier curves and surfaces are presented in [Deu98a, Fow92a] These methods are appropriate to render scenes for any viewing situation, even when the plants are very close to the viewer. Reeves [Ree85a] proposes a different technique for plant modeling that is also appropriate to render realistic scenes. His method is based on particle systems, where a blade of grass and other underbrush are represented by the trajectory of a particle. Unfortunately, both these methods are very computationally ....

Reeves, W. T., and Blan, R. Approximate and Probabilistic Algorithms for Shading and Rendering Structured Particle Systems. In Computer Graphics 19, pp. 313-322, 1985.

....number counting and visualization. Keywords Stochastic, substructure, tree growth, 3D plant simulation, fast algorithm 1. INTRODUCTION Since plant structures are diverse and irregular, stochastic geometrical parameters are often used in generating naturally looking image. For example, Reeves [Reev85] used random geometrical parameters drawn from uniform distribution to create stochastic trees with particle systems. Oppenheimer [Oppe86] drew statistically self similar tree by setting mean and standard deviation for parameters. Another kind of stochastic plant model was initiated by de ....

....is to represent similar objects with same data so that data storage drops down while the reduction of diversity cause only negligible visual impact. Instancing can be used in different levels thanks to hierarchical structure of plant and forest scene. This method was used in [Deus98] Hart92] [Reev85] to create plant figure. Recently, Yan [Yan02] presented an algorithm to construct rigid tree structure based on substructures. The current paper is a progress in the frame of GreenLab model. The automaton that is originally defined in [Zhao01] is used here as the topological model. In this ....

Reeves, W. T. and Blau, R. Approximate and probabilistic algorithms for shading and rendering structured particle systems. Computer Graphics 19, No. 3, pp. 313-322, 1985.

....whereas the stochastic model of [22] can. Dedicated tree rendering models On the other hand, several models dedicated to an efficient representation and rendering of trees and forests have been proposed, using ray tracing or real time techniques [16, 23] Reeves introduced the particles systems [19, 20]. This representation is dedicated to objects made of a huge amount of small long primitives that are drawn as simple strokes, well suitable for modeling trees. In his paper, the shadows are faked using a priori simple laws such as proportionality with depth inside a tree. Max proposed in [13] a ....

William T. Reeves and Ricki Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. In B. A. Barsky, editor, Computer Graphics (SIGGRAPH '85 Proceedings), volume 19(3), pages 313--322, July 1985.

....aspect of our problem, were an inspiration to us. They are described next. Object representations: The first obstacle for generating a virtual prairie is the number of geometric primitives that are needed. Rendering a geometric model for each blade of grass has been done using particle systems [10, 11]. But doing so with a sufficient frame rates and at the scale of a whole prairie is clearly impossible. Thus, coarser representations have to be generated. However, the prairie being a collection of many small objects rather than a single complex one, geometric methods such as polygons decimation ....

....we did not implement it, Lengyel s solution for soft shadowing would certainly be a good way of enhancing the visual realism of our prairies. Animation methods: A first method for generating a stochastic animation of fields of grass blowing in the wind is proposed by Reeves in the mid eighties [11], as an application of the particlebased modeling approach. Particles evolving in a 2D space are first used for modeling complex gusts of wind subject to random local variations of intensity. The resulting 2D wind maps are stored, for each animation step. Then, procedural trajectories are ....

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William T. Reeves and Ricki Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. In B. A. Barsky, editor, Computer Graphics (SIGGRAPH '85 Proceedings), volume 19(3), pages 313-- 322, July 1985.

....[SDB97] These methods are not well adapted to the high quality rendering of complex scenes poorly structured (e.g. forest) where parallax effects and specular highlights are reluctant to be cached. Conversely, some dedicated procedural rendering tools such as particle systems [Ree83] RB85] can be used to efficiently render some complex shapes, at the expense of using a limited repertoire of shading or reflectance models. Volumetric textures can provide a good trade off between generality and efficiency: the key concept, from the user s point of view, is the mapping of a replicated ....

....Strictly speaking, this is a density of occupation. We suppose it approximates not to bad the average ray occultation. Too small values for very thin objects are avoided thanks to the bias of our sampling, such as testing only the distance to the voxel center. tems and L systems [FvDFH90] RB85] PLH88] can be considered as primitive based techniques: these representations design a shape by combining simple shapes. Respectively, these primitive shapes are a solid, a facet, a skeleton element, a trajectory segment, and a terminal symbol. For a mesh, for instance, the distance function ....

William T. Reeves and Ricki Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. In B. A. Barsky, editor, Computer Graphics (SIGGRAPH '85 Proceedings), volume 19(3), pages 313--322, July 1985.

....above; color look up tables, allowing variations of the texture appearance without having to transfer the texture more than once. 2.4 Drops, burnt spots and whitened spots Little work has been done on drops. Drops used in CG applications are often based on particle systems (Reeves 1983; Reeves and Blau 1985) associating a fake visible object (a disk, a 2D sprite, a line segment) with a physically animated point object. Tears have been simulated in (Fournier et al. 1998) We do not need so much realism in the visual aspect, and we don t want to add hundreds of polygons in our scene, but we need the ....

Reeves, W. T. and R. Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. In B. A. Barsky (Ed.), Computer Graphics (SIGGRAPH '85 Proceedings), Volume 19(3), pp. 313-- 322.

....clusters of leaves is increased by the amount of ambient light denoted by Phi a , presented in the crown of the tree. In our simulation, we use 10 of total light flux of the hemisphere Phi a = 0:1 Phi: We use constant amount of ambient light in the crown, although we know that Reeves and Blau [16] use exponential scaling of this coefficient in their simulation. It does not change the shape of the plant significantly if directional light fluxes are considered. 4.3 Oscillation of leaves One of the disadvantages of this kind of sampling is that planar leaves sampled in the direction ....

W. Reeves and R. Blau. Approximate and Probabilistic Algorithms for Shading and Rendering Structured Particle Systems. In Proceedings of SIGGRAPH '85, volume 19(3), pages 313--322, 1985.

....and attributes of tree surface (i.e. deformations, deviations, bumps, coloring, etc. A great effort has been spent in recent years addressing the problems of producing realistic images of trees. These efforts include work on fractals [Smit84] geometric models [Aono84] particle systems [Reev85], textured surfaces [Gard84] Bloo85] L Systems [Prus90] combinatorial analysis [Vien89] and developmental botanical models [Reff88] Holt94] Regardless of the model used for the construction of trees, the principal elements of their representation are geometry and texture. Being the texture ....

W.T. Reeves and R. Blau, "Approximate and probabilistic algorithms for Shading and Rendering Structured Particle Systems", 1985, Computer Graphics, vol. 19, no. 3, pp. 313--322

....(components of the model) at the time of daughter creation, is the most frequently simulated form of endogenous control, although many models have been formulated without referring to this term explicitly. For example, tree models proposed by Aono and Kunii [1] Bloomenthal [5] Reeves and Blau [32], Oppenheimer [25] and de Reffye and his collaborators [10, 19] are all controlled by lineage. In contrast, interactive mechanisms involve information flow between coexisting adjacent components of the developing structure. In a growing plant, this information may be represented by phytohormones, ....

W.T. Reeves and R. Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. Proceedings of SIGGRAPH '85 (San Francisco, California, July 22-26,

.... on models by Honda [18] Francon [10] observed that L systems can also capture the models of tree architecture classified by Hall e et al. 15] and the AMAP models originated by de Reffye [5] Stochastic L systems can emulate grass models described in terms of particle systems by Reeves and Blau [34] (Plate 4) Further analysis is needed to establish detailed relationships between these classes. Map L systems Map L systems [22] extend the expressive power of L systems beyond branching structures to graphs with cycles, called maps, representing cellular layers. Their geometrical ....

W. T. Reeves and R. Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. Proceedings of SIGGRAPH '85 (San Francisco, California, July 22-26,

....stochastic model that may be adjusted to approximately emulate a range of different phenomena reduces the need to develop procedures to model each of these phenomena individually. For these reasons, stochastic techniques have assumed a leading role in the synthesis of complex images (e.g. [10, 35, 36, 43, 31]) The usefulness of a particular stochastic model depends on both its computational advantages and on the extent to which it can be adjusted to describe different phenomena. The stochastic fractal techniques are somewhat limited in descriptive power in that they model only power spectra of the ....

Reeves, W. and Blau, R. Approximate and probabilistic algorithms for shading and rendering structured particle systems. In Siggraph 85 Proceedings. (San Francisco, Calif., July) ACM, New York, 1985, 313-322.

....and combined them with stones and ground materials. Alvy Ray Smith, one of the early authors dealing with fractals and formal plant descriptions created a cartoon tree with small disks representing bunches of leaves [19] A similar representation with smaller disks was used by Reeves and Blau [14] to constitute their structured particle systems for rendering realistic trees. The idea of representing numerous botanical leaves by an abstract geometric primitive inspired us (like Kowalski et al. 7] to work on pen andink illustrations of trees. A line drawing is usually created by combining ....

W. T. Reeves and R. Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. In Computer Graphics (SIGGRAPH '85 Proceedings), volume 19, pages 313--322, July 1985.

....used for clouds toalso display smoke. It seems to be natural to think of modelling the smoke as a set of smoke particles. The particle system is popular for natural phenomena. In this method, gas is dealt with as a set of particles. Reeves [1] Ebert, Carlson, and Parent [2] and Reeves and Blau [3] displayed smoke by using the particle system. However, to model the density distribution of the smoke requires a large number of particles. One of the methods to model the density distribution of smoke is to define a function that shows the density distribution of smoke or clouds. Musgrave ....

W.T. Reeves, and R. Blau, "Approximate and Probabilistic Algorithms for Shading and Rendering Structed Particle Systems, " Proc. of SIGGRAPH'85, 1985, pp.313-322.

....that are stuck to surfaces, we eliminate both the shower door effect and random temporal noisiness. Reeves first presented an algorithm for rendering particles without using traditional 3D models to represent them, instead drawing them as circles and motion blurred line segments in screen space [10]. We also render particles in screen space, but use 2d brush stroke shapes instead of circles and line segments. Rendering 2d shapes in screen space is one of the core concepts of our work. Fleischer et al. 2] described a similar method, except they place 3d geometric elements on surfaces in ....

....painted, we can imagine incorporating this look with traditional rendering methods. For example, when artists depict foliage, they don t paint every leaf. Instead, they use brush strokes to abstractly represent the leaves. Certainly particle rendering methods have been used for this purpose before [10], but we believe our technique can eliminate complex modeling issues such as generating realistic tree models made of particles, and that the level of control we provide for achieving different looks will prove to be a more powerful but easier to use tool. We foresee using this method to render ....

William T. Reeves and Ricki Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. In Computer Graphics (SIGGRAPH '85 Proceedings) , volume 19, pages 313--322, July 1985.

....allow us to observe the evolution of crowd flows at different levels of resolution. There is very little literature which directly concerns the simulation of human hair structure using particle systems. Particle systems have been previously used by Reeves [7] to model fire and by Reeves and Blau [8] to represent tree and grass. The application of our method is exposed for human hair representation, but can also be applied to those former works. Usual hair structure of a human is composed of 100000 to 200000 strands of hair, whose diameter ranges from 40 to 120. In [5] Rosenblum, Carlson and ....

W.T.Reeves. Approximate and probabilistic algorithms for shading and rendering structured particle systems. IEEE Computer Graphics, 19(3):313-- 322, 1985. A. APPRENDIX We give here the result of an approximation at several resolutions of the model described in section 3.4 (

....The only force af UNC CH TR 00 007 fecting particles after their creation was gravity, yielding parabolic paths for all particles. The great complexity achieved by these particle systems stemmed mainly from complex, stochastic initial values, not from complex dynamics. Reeves follow on paper, [Reeves 1985], includes more sophisticated particle motion for grass and introduces constrained particles for modeling solid objects like grass and trees. Reynolds 1987] introduces Boids, which represent individual birds or other animals that flock or school in a realisticappearing manner. Boids can be seen ....

Reeves, W. T. and R. Blau. "Approximate and Probabilistic Algorithms for Shading and Rendering Structured Particle Systems". Proc. of SIGGRAPH '85, San Francisco, California, July, 1985.

....them will no longer be justified, given that they only occupy sub pixel areas in image space. The alternatives explored currently in the research community are higher order surfaces or simpler primitives such as points. Points became popular in particular with the introduction of particle systems [17] but have also been used by rendering systems as the final target for subdividing more complex modeling primitives [4] Today they have seen a comeback in image based rendering and real time graphics due to their modeling flexibility, efficiency, and ease of acquisition with digital cameras, 3D ....

W. T. Reeves and R. Blau: "Approximate and Probabilistic Algorithms for Shading and Rendering Structured Particle Systems". Proc. SIGGRAPH '85, pp 313-322, 1985.

....of the resulting image. A common method is to render single objects of a scene with the appropriate method and compose the images with an a channel. Reeves used particle systems and probabilistic algorithms to render complex natural scenes with an a channel related technology called frame buffer [REEV85]. Complex reflections and the casting of shadows, like those of trees onto terrain or themselves, can only be accomplished approximatively in this way. For the purpose of a consistent rendering method, where all objects are visualized in a uniform way and can mutually influence their appearance, ....

Reeves W.T., Approximate and Probabilistic Algorithms for Shading and Rendering Structured Particle Systems, ACM Computer Graphics SIGGRAPH Proc. 1985, Vol. 19, No. 3, pp. 313, 1985

....of a surface element from every direction. b) Point Sample Rendering stores a single point with colour and normal and computes views from arbitrary directions using the current lighting model Points have often been used to model soft objects such as smoke, clouds, dust, fire, water and trees [Reeves83, Smith84, Reeves85]. The idea of using points to model solid objects was mentioned nearly two decades ago by Csuri et al. Csuri79] and was briefly investigated by Levoy and Whitted some years later for the special case of continuous, differentiable surfaces [Levoy85] In 1988 Cline et al. generated surface points ....

William T. Reeves, "Approximate and Probabilistic Algorithms for Shading and Rendering Structured Particle Systems", Computer Graphics (SIGGRAPH '85 Proceedings), Vol 19, No. 3, pp. 313-322

....of logging on the landscape, visualization of models of ecosystems for research and educational purposes, and synthesis of scenes for computer animations, drive and flight simulators, games, and computer art. Beautiful images of forests and meadows were created as early as 1985 by Reeves and Blau [50] and featured in the computer animation The Adventures of Andr e and Wally B. 34] Reeves and Blau organized scene modeling as a sequence of steps: specification of a terrain map that provides the elevation of points in the scene, interactive or procedural placement of vegetation in this terrain, ....

....synthesis of natural scenes reflects the quest for a good tradeoff between the realism of the images and the amount of resources needed to generate them. The scenes synthesized by Reeves and Blau were obtained using (structured) particle systems, with the order of one million particles per tree [50]. To handle large numbers of primitive elements contributing to the scene, the particle models of individual trees were generated procedurally and rendered sequentially, each model discarded as soon as a tree has been rendered. Consequently, the size of memory needed to generate the scene was ....

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W. T. Reeves and R. Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. Computer Graphics (SIGGRAPH 85 Proceedings), 19(3):313--322, 1985.

....natural phenomena has mostly been possible only via computationally intensive physically based simulations. For example, steam, fog, smoke, and fire have been simulated in this manner [15, 13, 27, 28] Explosions, fire, and waterfalls have been successfully simulated by animated particle systems [23, 24, 26]. Simplified physically based models have also been used to produce synthetic waves and surf [17, 21] While the techniques mentioned above have been able to generate impressive results of compelling realism, a custom tailored model must be developed for each type of simulated phenomena. ....

William T. Reeves and Ricki Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. In B. A. Barsky, editor, Computer Graphics (SIGGRAPH '85 Proceedings), volume 19, pages 313--322, July 1985.

....top of the underlying geometry based on information derived from the associated surface s position in screen space. 2 Related Work Particle systems in general have been used extensively in photorealistic scenes to render complex textures and objects on top of simple geometric structures. Reeves [9] used particle systems to create trees and other complex objects. Fleischer et al. 2] used particle systems to render biologically based cellular textures. Meier [7] showed that particle based brush strokes could be used to produce painterly renderings. Her work is a precursor to our technique, ....

William T. Reeves and Ricki Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. Computer Graphics (Proceedings of SIGGRAPH 85), 19(3):313--322, July 1985. Held in San Francisco, California.

....natural phenomena has mostly been possible only via computationally intensive physically based simulations. For example, steam, fog, smoke, and fire have been simulated in this manner [16, 14, 30, 31] Explosions, fire, and waterfalls have been successfully simulated by animated particle systems [25, 26, 28]. Simplified physically based models have also been used to produce synthetic waves and surf [18, 23] While the techniques mentioned above have been able to generate impressive results of compelling realism, a custom tailored model must be developed for each type of simulated phenomena. ....

William T. Reeves and Ricki Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. In B. A. Barsky, editor, Computer Graphics (SIGGRAPH '85 Proceedings), volume 19, pages 313--322, July 1985.

....a specific representation and the mean to render it. The first category concerns L systems, fractals, botanical and physical models [Smi84, PLH88, dREF 88, FR86] which generate polygons. The second category mostly concerns particle systems and some landscape specialized models [Ree83, RB85, WP95] which use specific representations and rendering techniques. Procedural geometric models do not address the rendering aspect of the problem, and specific representations forbid the use of general modeling tools and existing databases. The integration of different kinds of objects in a ....

....the whole volume systematically, and is quite costly. Moreover, not only do we need to know the voxel occupation, but also the local reflectance, which implies that the method has to be extended. CSG, polygonal meshes, implicit functions, particle systems and L systems [FvDFH90, Smi84, Ree83, RB85, PLH88] are primitive based techniques : these constructions design a shape by combining simple shapes (the primitives being respectively a solid, a facet, a skeleton element, a trajectory segment, a terminal symbol) The simplicity of these primitives allows more efficient and accurate ....

William T. Reeves and Ricki Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. In B. A. Barsky, editor, Computer Graphics (SIGGRAPH '85 Proceedings) , volume 19(3), pages 313--322, July 1985.

....elements, and the particular methods used to mimic Dr. Seuss s and Geoffrey Hayes s [7] styles. 2 Prior Work Using art as a motivation for computer graphics techniques is not new, and our work builds on the efforts of many others. Fundamental to our ideas are the particle systems of Reeves [12, 13], which he used to create trees, fireworks, and other complex imagery from relatively simple geometry. Alvy Ray Smith s later use of particles, together with recursively defined L systems that he called graftals, extended this to more biologically accurate tree and plant models [15] His ....

William T. Reeves and Ricki Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. In SIGGRAPH 85 Conference Proceedings, pp. 313--322. ACM SIGGRAPH, July 1985.

....these effects in a physically accurate way, but the methods available to do so are inefficient, and tailored to computational fluid mechanics rather than computer graphics. Another popular method has been to treat gases as collections of particles. Ebert, Carlson, and Parent [3] Reeves and Blau [11], and Stam and Fiume [17] reduced the complexity of the gas volume modeling problem in this way by using discrete particles to represent gaseous motion. Particle systems are generally efficient, but have two inherent drawbacks. First, a real gas is a continuous medium; selecting particular ....

Reeves, W.T., and Blau, R., "Approximate and Probabilistic Algorithms for Shading and Rendering Structured Particle Systems ", SIGGRAPH '85, Computer Graphics 19(3), 1985, pp. 313--322.

....The simulation module produces a data base of hair segments for each frame, that are used as input for the rendering module. In our system, hair rendering is done by raytracing using a modified version of the public domain Rayshade program. An implementation module of the shadow buffer algorithm [H8][H9] H13] has been added to the public domain RAYSHADE program, based on an earlier version of hair rendering based on pixel blending [H5] It works fine for calculating shadows of normal objects and is also used to figure out the shadows cast by hair. In the hair rendering module, the process is ....

Reeves W.T., Blau R. (1985) "Approximate and Probabilistic Algorithm for Shading and Rendering Structured Particle Systems", Computer Graphics 19(3), pp. 313-322.

....represented as raster points in the simplest of schemes. As these particles are advected, their raster positions are updated and the motion of the particle can be studied. Just using raster points can lead to clutter and a meaningless image when many particles are displayed simultaneously. Reeves [77, 78] introduced structured particle systems for representing fuzzy objects. These were applied to image synthesis to produce fuzzy phenomena such as grass, trees, fire and waterfalls. Sims [83] developed a parallel system for handling particles with hidden surfaces and anti aliasing and applied these ....

....[41] developed a model for rendering teddy bear fur. They developed and used anisotropic volume textures, which they called texels. Watanabe [93] describes techniques to render hair using connected prisms. They also describe physically based models for the bending and shaping of the hair. Reeves [77, 78] particle systems have been used to generate a variety of fuzzy phenomena such as grass, trees and fire. 86 7.2 Hair Splats Hair splats are similar to line bundles and are more volume oriented than surface oriented. How they are applied to different visualization tasks can vary greatly, as will ....

Reeves, W.T. and R. Blau, Approximate and Probabilistic Algorithms for Shading and Rendering Structured Particle Systems. Computer Graphics, July 1985. 19(3): p. 313-322.

....create the fire that sweeps over a planet in the Genesis Sequence of the movie Star Trek II: The Wrath of Khan. He defined a particle system model as a cloud of primitive particles, where each particle is generated into the system, moves, changes form and color, and then dies. Reeves and Blau [44] present the concept of structured particle systems to create trees and grass. Others have utilized particle systems to simulate a variety of physical phenomena [10, 26] Sims [50] demonstrated how particle systems could be efficiently implemented on a massively parallel computer to produce ....

Reeves, W.T. and R. Blau, "Approximate and Probabilistic Algorithms for Shading and Rendering Structured Particle Systems," Computer Graphics (Proc. SIGGRAPH), Vol. 19, No. 3, pp. 313-322, July 1985.

....2.1 Particle systems Particle Systems were first used in computer graphics by Reeves in 1983 [36] He defined a particle system model as a cloud of primitive particles, where each particle is generated into the system, moves, ages, and then dies. This work was later extended by Reeves and Blau [37], Fournier and Reeves [20] Sims [42] and many others to model such diverse phenomena as trees and grass, ocean spray, fireworks, waterfalls, fire, snowstorms and explosions. Reynolds [38] in his work on flocking behavior, greatly enhanced the power of the particle system as a modeling tool. He ....

Reeves, W.T. and R. Blau, "Approximate and Probabilistic Algorithms for Shading and Rendering Structured Particle Systems," Computer Graphics (Proc. SIGGRAPH), Vol. 19, No. 3, pp. 313-322, July 1985.

....Sims [14] and Wejchert and Haumann [17] model a wind field as the superposition of deterministic fields. Modelling a visually convincing turbulent wind field this way is painstaking. The greatest success in this direction was the particle based Blowing in the Wind animation by Reeves and Blau [10]. Stochastic modelling is a natural alternative strategy. In [13] Shinya and Fournier describe an approach developed independently of ours but which has some similarities. They employ stochastic processes and Fourier synthesis to derive a wind field in spatiotemporal frequency domain, and invert ....

W. T. Reeves and R. Blau. "Approximate and Probabilistic Algorithms for Shading and Rendering Structured Particle Systems". ACM Computer Graphics (SIGGRAPH '85), 19(3):313--322, July 1985.

....of the potentially complicated interdependenciesof the elements, it is difficult to create either geometric or textural models of such objects by hand. So we turn to automatic data amplification techniques, which are similar to the structured particle systemsused to generate models of plants [26, 30]. Developmental Approach For generating organic patterns, it is natural to consider a biologically based simulation. In previous work [8] we developed a biological developmental model to simulate and study patterns generated by the motions and interactions of discrete cells (Figure 3) These ....

....further distances are rendered with fewer polygons. The bottom image shows a closeup of the nearest and furthest objects, so we can see the reduced number of polygons. thorny spheres in Figure 7. Rendering an appropriately scaled representation One of the drawbacks of data amplification techniques [30, 26] such as ours is their ability to generate a ridiculous amount of geometry to render. To ameliorate this, we use the particle converter to choosegeometric primitives appropriate to the size of the object in the final image (Figure 4) This approach could be carried even further,for instance, by ....

William T. Reeves and Ricki Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. In Computer Graphics (SIGGRAPH '85 Proceedings), volume 19, pages 313--322, July 1985.

....simulation, collision detection. 1 Introduction Particle computer simulations are an established technique used in many fields including physics, fluid mechanics and biomechanics. Recently particle systems have been used to solve a surprisingly wide spectrum of problems in computer graphics [29, 28, 33, 25, 3, 4, 22, 23, 20, 24, 18, 30, 10]. Although their utility can hardly be questioned, they have a serious weakness: they become prohibitively slow as the number of particles increases and consequently present a serious computational challenge. The current methods cannot provide interactive speeds for all but prohibitively small ....

William T. Reeves and Ricki Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. In B. A. Barsky, editor, Computer Graphics (SIGGRAPH '85 Proceedings), volume 19, pages 313--322, July 1985.

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W. T. Reeves and R. Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. Computer Graphics, 19(3):313-322, July 1985.

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REEVES W., BLAU R.: Approximate and probabilistic algorithms for shading and rendering structured particle systems. In Computer Graphics (SIGGRAPH '85 Proceedings) (July 1985), vol. 19(3), pp. 313--322. 2

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W. Reeves and R. Blau. "Approximate and Probabilistic Algorithms for Shading and Rendering Structured Particle Systems". SIGGRAPH 1985, pp. 313-322.

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Reeves, W., and Blau, R. Approximate and Probabilistic Algorithms for Shading and Rendering Structured Particle Systems. SIGGRAPH '85. p. 313-322. 1985

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W. T. Reeves and R. Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. In Computer Graphics (SIGGRAPH '85 Proceedings), volume 19, pages 313--322, July 1985.

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W. T. Reeves and R. Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. In Computer Graphics (SIGGRAPH '85), volume 19(3), pages 313--322, July 1985.

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REEVES W., BLAU R.: Approximate and probabilistic algorithms for shading and rendering structured particle systems. In Computer Graphics (SIGGRAPH '85 Proceedings) (July 1985), vol. 19(3), pp. 313--322. 2

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William T. Reeves and Ricki Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. In SIGGRAPH 85, Conference Proceedings, Annual Conference Series. ACM SIGGRAPH, 1985.

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W.T. Reeves, "Approximate and Probabilistic Algorithms for Shading and Rendering Structured Particle Systems", SIGGRAPH '85 Proceedings, pp. 313-322

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Reeves, William, and Blau, Ricki. Approximate and Probabilistic Algorithms for Shading and Rendering Structured Particle Sytems. Proceedings of SIGGRAPH'85 (San Francisco, California, July 22-26,

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W. T. Reeves, Approximate and Probabilistic Algorithms for Shading and Rendering Structured Particle Systems. Computer Graphics, vol. 19, no. 3, pp 313-322, 1985.

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Reeves, W.T.and Blau, R., "Approximate and Probabilistic Algorithms for Shading and Rendering Structured Particle Systems," Computer Graphics, 19(3), pp. 313-322 (July 1985).

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W. Reeves and R. Blau. "Approximate and Probabilistic Algorithms for Shading and Rendering Structured Particle Systems". SIGGRAPH 1985, pp. 313-322.

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Reeves, W.T., and Blau, R., #Approximate and Probabilistic Algorithms for Shading and Rendering Structured Particle Systems ", SIGGRAPH '85, Computer Graphics 19#3#, 1985, pp. 313#322.

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William Reeves and Riki Blau. Approximate and probabilistic algorithms for shading and rendering structured particle systems. Computer Graphics, 19(3):313--322, 1985. ACM SIGGRAPH Conference Proceedings.

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