Discrete Event Simulation Implemented in a Virtual Environment

Virtual reality (VR) technology provides a human-computer interface that allows participants to interact naturally with digital objects which are represented as three-dimensional images that occupy positions in a three-dimensional world. Related to problems of engineering design and manufacturing, this new technology offers engineers the ability to work with computer models in a three-dimensional, immersive environment. This paper describes a virtual reality application where the results of a discrete event simulation of a manufacturing cell are integrated with a virtual model of the cell to produce a virtual environment. The program described in this paper, the VRFactory, combines results from a commercial discrete event simulation program, SLAM II, with a virtual environment. This allows the user to investigate, using three-dimensional computer models, how various changes to the manufacturing cell affect part production. This investigation is performed while immersed in a computer-generated three-dimensional representation of the cell. Existing discrete event programming software allows only two-dimensional views of the factory as the parts progress through the simulation. Parts are shown only as primitive geometric shapes on the computer monitor and instantaneously move from one station to the next. The virtual environment implementation of the SLAM II results allows users to experience the simulation in a fully immersive three-dimensional digital environment. The virtual environment used here is a CAVE™-like projection screen-based facility called the C2, which is located at Iowa State University. This paper describes the creation of the VR model of the manufacturing cell, the animation of the environment and the implementation of the results of the discrete event simulation

Collage Sculptures

In this thesis, I develop a program to automatically assemble collage sculptures, sets of arbitrary, non-overlapping elements arranged to fill out a recognizable target shape according to a set of procedural rules. A user provides the target and element shapes and the program procedurally places the elements in spherical holes in the target space. A signed distance function defined over the target space keeps track of the remaining holes to fill. Elements are preprocessed to determine the size of their smallest enclosing bounding sphere. They are placed in holes based on the radius of their bounding sphere. After each placement, the signed distance function is efficiently updated to account for the newly added element. Elements are placed from largest to smallest, filling the space to a predefined threshold. To demonstrate this program, I generated a number of collage sculptures. In accordance with our procedural rules, the elements in the resulting collage sculptures recognizably represent the target shape, do not overlap, are not deformed from their original shape, and display variety in size, position, and orientation

Implicit Decals: Interactive Editing of Repetitive Patterns on Surfaces

11 pagesInternational audienceTexture mapping is an essential component for creating 3D models and is widely used in both the game and the movie industries. Creating texture maps has always been a complex task and existing methods carefully balance flexibility with ease of use. One difficulty in using texturing is the repeated placement of individual textures over larger areas. In this paper we propose a method which uses decals to place images onto a model. Our method allows the decals to compete for space and to deform as they are being pushed by other decals. A spherical field function is used to determine the position and the size of each decal and the deformation applied to fit the decals. The decals may span multiple objects with heterogeneous representations. Our method does not require an explicit parameterization of the model. As such, varieties of patterns including repeated patterns like rocks, tiles, and scales can be mapped. We have implemented the method using the GPU where placement, size, and orientation of thousands of decals are manipulated in real time

The VR Factory : discrete event simulation implemented in a virtual environment

http://www.worldcat.org/oclc/3970218

Implémentation par automates cellulaires d'une modélisation architecturale de rétine biologique

Cet article traite de l'implémentation sur calculateur classique d'une modélisation cellulaire de la rétine biologique via deux mod`eles d'automates cellulaires (2D et 3D). Les algorithmes utilisés dans cet objectif, pénalisants en temps de calcul, nécessitent la plupart du temps une architecture de traitement spécifique et par conséquent, une adaptation de l'algorithme. Notre solution alternative utilise les fonctionnalités de composants logiciels de synthèse d'images enfouissables en partie dans la carte graphique pour permettre la parallélisation des traitements cellulaires

Collage Sculptures

In this thesis, I develop a program to automatically assemble collage sculptures, sets of arbitrary, non-overlapping elements arranged to fill out a recognizable target shape according to a set of procedural rules. A user provides the target and element shapes and the program procedurally places the elements in spherical holes in the target space. A signed distance function defined over the target space keeps track of the remaining holes to fill. Elements are preprocessed to determine the size of their smallest enclosing bounding sphere. They are placed in holes based on the radius of their bounding sphere. After each placement, the signed distance function is efficiently updated to account for the newly added element. Elements are placed from largest to smallest, filling the space to a predefined threshold. To demonstrate this program, I generated a number of collage sculptures. In accordance with our procedural rules, the elements in the resulting collage sculptures recognizably represent the target shape, do not overlap, are not deformed from their original shape, and display variety in size, position, and orientation

A Multiple-Mechanism Developmental Model for Defining Self-Organizing Geometric Structures

This thesis introduces a model of multicellular development. The model combines elements of the chemical, cell lineage, and mechanical models of morphogenesis pioneered by Turing, Lindenmayer, and Odell, respectively. The internal state of each cell in the model is represented by a time-varying state vector that is updated by a differential equation. The differential equation is formulated as a sum of contributions from different sources, describing gene transcription, kinetics, and cell metabolism. Each term in the differential equation is multiplied by a conditional expression that models regulatory processes specific to the process described by that term. The resulting model has a broader range of fundamental mechanisms than other developmental models. Since gene transcription is included, the model can represent the genetic orchestration of a developmental process involving multiple mechanisms. We show that a computational implementation of the model represents a wide range of biologically relevant phenomena in two and three dimensions. This is illustrated by a diverse collection of simulation experiments exhibiting phenomena such as lateral inhibition, differentiation, segment formation, size regulation, and regeneration of damaged structures. We have explored several application areas with the model: Synthetic biology. We advocate the use of mathematical modeling and simulation for generating intuitions about complex biological systems, in addition to the usual application of mathematical biology to perform analysis on a simplified model. The breadth of our model makes it useful as a tool for exploring biological questions about pattern formation and morphogenesis. We show that simulated experiments to address a particular question can be done quickly and can generate useful biological intuitions. As an example, we document a simulation experiment exploring inhibition via surface chemicals. This experiment suggests that the final pattern depends strongly on the temporal sequence of events. This intuition was obtained quickly using the simulator as an aid to understanding the general behavior of the developmental system. Artificial evolution of neural networks. Neural networks can be represented using a developmental model. We investigate the use of artificial evolution to select equations and parameters that cause the model to create desired structures. We compare our approach to other work in evolutionary neural networks, and discuss the difficulties involved. Computer graphics modeling. We extend the model to allow cells to sense the presence of a 3D surface model, and then use the multicellular simulator to grow cells on the surface. This database amplification technique enables the creation of cellular textures to represent detailed geometry on a surface (e.g., scales, feathers, thorns). In the process of writing many developmental programs, we have gained some experience in the construction of self-organizing cellular structures. We identify some critical issues (size regulation and scalability), and suggest biologically-plausible strategies for addressing them

Stochastic microgeometry for displacement mapping

Proceedings of Shape Modeling International 2005, June 2005, pp. 164-173. Retrieved 3/16/2006 from http://www.cs.drexel.edu/~david/Papers/schroeder_SMI05.pdf.Creating surfaces with intricate small-scale features (microgeometry) and detail is an important task in geometric modeling and computer graphics. We present a model processing method capable of producing a wide variety of complex surface features based on displacement mapping and stochastic geometry. The latter is a branch of mathematics that analyzes and characterizes the statistical properties of spatial structures. The technique has been incorporated into an interactive modeling environment that supports the design of stochastic microgeometries. Additionally a tool has been developed that provides random exploration of the technique's entire parameter space by generating sample microgeometry over a broad range of values. We demonstrate the effectiveness of our technique by creating diverse, complex surface structures for a variety of geometric models, e.g. arrowheads, candy bars, busts, planets and coral

The morphological development of a wood burl shader

In the field of computer graphics, shaders provide an interface between lights and surfaces, giving the appearance of metal, plastic, wood, etc. As the field progresses, more and more shaders are required to simulate a wider and wider variety of materials. We present a new shader for the simulation of wood burl, a complex material used in furniture, art, car interiors, and a host of other luxury items. This shader was developed through a morphological approach - a study of the original material, its structure, and growth. Consequently, research began with a thorough look at wood burl, polished and unpolished, in an assortment of different species. We discovered the appearance can be broken into three sub-appearances - knots, curl, and a subtle undergrain. These three sub-appearances interact to create the characteristic swirls and whorls of burl. For the subtle undergrain, we used a common oak shader, added noise, and faded it into the background. We then developed a system of randomly placing points through the material to act as knots. Since the knots grow and distort the surrounding grain, we used distance-scaled forces to push the surface coordinates around and between all the knots. When the oak shader is applied, it appears to swirl and curl around the knots, much like a stream between rocks. This created the first level of curl or swirly grained wood, but one level alone appeared flat. To solve this, we procedurally blended levels of curl to give a look of increased depth. Finally, we added reflection, gloss, and other surface properties to give a look of warmth and polish. All of these properties are controlled by a set of parameters in the shader's interface. By adjusting these parameters, the user can emulate a variety of different burl types