Controlling Rigid Bodies with Dynamic Constraints

We present a technique, "Dynamic Constraints," for controlling the positions and orientations of rigid bodies n computer graphics models. The technique addresses the issue of providing control over a physically-based model, in which the bodies' behavior is determined by simulation of Newton's Laws of Motion. The "Dynamic Constraints" technique allows the modeler to control the configuration of bodies in a model by specifying constraints which must be met and maintained, as the simulation unfolds. To meet the constraints, we introduce forces into the model; these "constraint forces" forces are applied to the bodies that are constrained. We use an inverse dynamics method to derive a linear "constraint-force equation," whose solution yields the values of the constraint forces. We continually solve the constraint-force equation during the simulation of a model, so that the bodies' behavior will be consistent with the constraints. This thesis is accompanied by a narrated 10 -minuted videotape, "Caltech Modeling Demos, 1987" that contains several animations demonstrating the "Dynamic Constraints" technique. This thesis additionally includes a glossary of terms relating to physically-based modeling and dynamic constraints

A structured approach to physically-based modeling for computer graphics

This thesis presents a framework for the design of physically-based computer graphics models. The framework includes a paradigm for the structure of physically-based models, techniques for "structured" mathematical modeling, and a specification of a computer program structure in which to implement the models. The framework is based on known principles and methodologies of structured programming and mathematical modeling. Because the framework emphasizes the structure and organization of models, we refer to it as "Structured Modeling." The Structured Modeling framework focuses on clarity and "correctness" of models, emphasizing explicit statement of assumptions, goals, and techniques. In particular, we partition physically-based models, separating them into conceptual and mathematical models, and posed problems. We control complexity of models by designing in a modular manner, piecing models together from smaller components. The framework places a particular emphasis on defining a complete formal statement of a model's mathematical equations, before attempting to simulate the model. To manage the complexity of these equations, we define a collection of mathematical constructs, notation, and terminology, that allow mathematical models to be created in a structured and modular manner. We construct a computer programming environment that directly supports the implementation of models designed using the above techniques. The environment is geared to a tool-oriented approach, in which models are built from an extensible collection of software objects, that correspond to elements and tasks of a "blackboard" design of models. A substantial portion of this thesis is devoted to developing a library of physically-based model "modules," including rigid-body kinematics, rigid-body dynamics, and dynamic constraints, all built with the Structured Modeling framework. These modules are intended to serve both as examples of the framework, and as potentially useful tools for the computer graphics community. Each module includes statements of goals and assumptions, explicit mathematical models and problem statements, and descriptions of software objects that support them. We illustrate the use of the library to build some sample models, and include discussion of various possible additions and extensions to the library. Structured Modeling is an experiment in modeling: an exploration of designing via strict adherence to a dogma of structure, modularity, and mathematical formality. It does not stress issues such as particular numerical simulation techniques or efficiency of computer execution time or memory usage, all of which are important practical considerations in modeling. However, at least so far as the work carried on in this thesis, Structured Modeling has proven to be a useful aid in the design and understanding of complex physically based models.</p

We don’t do Google, we do massive attacks: Notes on creative R&D collaborations

The article presents findings from an exploratory study investigating the nature of collaborative research and development in creative industries. Participants in the study are two creative SMEs with extensive experience of participating in collaborative projects. A collective case study approach is adopted with data collected on the factors impinging on the effectiveness of such collaborations. Findings are presented at the macro and micro levels of such collaborations. The paper concludes with a summary of some of the challenges faced by small creative SMEs when collaborating with other organizations during the research and development process

Adjustable tools: an object-oriented interaction metaphor

To provide a simpler metaphor for representing, selecting, and adjusting collections of attributes for interactive operations

Adjustable tools: an object-oriented interaction metaphor

To provide a simpler metaphor for representing, selecting, and adjusting collections of attributes for interactive operations

A modeling system based on dynamic constraints

We present "dynamic constraints," a physically-based technique for constraint-based control of computer graphics models. Using dynamic constraints, we build objects by specifying geometric constraints; the models assemble themselves as the elements move to satisfy the constraints. The individual elements are rigid bodies which act in accordance with the rules of physics, and can thus exhibit physically realistic behavior. To implement the constraints, a set of "constraint forces" is found, which causes the bodies to act in accordance with the constraints; finding these "constraint forces" is an inverse dynamics problem