Digital sculpture : conceptually motivated sculptural models through the application of three-dimensional computer-aided design and additive fabrication technologies

Thesis (D. Tech.) - Central University of Technology, Free State, 200

Virtual Clay for Direct Hand Manipulation

International audienceIn order to make virtual modeling as easy as real clay manipulation, we describe a realtime virtual clay model, specially designed for direct hand manipulation. We build on a previous layered model for clay, extending it to handle local properties such as colour or fluidity, to deal with an arbitrary number of tools, and to capture twist effects due to rotating tools. The resulting clay model is the first step towards a more long term goal, namely direct interaction through video tracking of the user's hands

Mutable elastic models for sculpting structured shapes

Special Issue: Proc. Eurographics, May 2013, Girona, Spain.International audienceIn this paper, we propose a new paradigm for free-form shape deformation. Standard deformable models minimize an energy measuring the distance to a single target shape. We propose a new, "mutable" elastic model. It represents complex geometry by a collection of parts and measures the distance of each part measures to a larger set of alternative rest configurations. By detecting and reacting to local switches between best-matching rest states, we build a 3D sculpting system: It takes a structured shape consisting of parts and replacement rules as input. The shape can subsequently be elongated, compressed, bent, cut, and merged within a constraints-based free-form editing interface, where alternative rest-states model to such changes. In practical experiments, we show that the approach yields a surprisingly intuitive and easy to implement interface for interactively designing objects described by such discrete shape grammars, for which direct shape control mechanisms were typically lacking

Expressive cutting, deforming, and painting of three-dimensional digital shapes through asymmetric bimanual haptic manipulation

Practitioners of the geosciences, design, and engineering disciplines communicate complex ideas about shape by manipulating three-dimensional digital objects to match their conceptual model. However, the two-dimensional control interfaces, common in software applications, create a disconnect to three-dimensional manipulations. This research examines cutting, deforming, and painting manipulations for expressive three-dimensional interaction. It presents a cutting algorithm specialized for planning cuts on a triangle mesh, the extension of a deformation algorithm for inhomogeneous meshes, and the definition of inhomogeneous meshes by painting into a deformation property map. This thesis explores two-handed interactions with haptic force-feedback where each hand can fulfill an asymmetric bimanual role. These digital shape manipulations demonstrate a step toward the creation of expressive three-dimensional interactions

Interactive simulation of fire, burn and decomposition

This work presents an approach to effectively integrate into one unified modular fire simulation framework the major processes related to fire, namely: a burning process, chemical combustion, heat distribution, decomposition and deformation of burning solids, and rigid body simulation of the residue. Simulators for every stage are described, and the modular structure enables switching to different simulators if more accuracy or more interactivity is desired. A “Stable Fluids” based three gas system is used to model the combustion process, and the heat generated during the combustion is used to drive the flow of the hot air. Objects, if exposed to enough heat, ignite and start burning. The decomposition of the burning object is modeled as a level set method, driven by the pyrolysis process, where the burning object releases combustible gases. Secondary deformation effects, such as bending burning matches and crumpling burning paper, are modeled as a proxy based deformation. Physically based simulation, done at interactive rates, enables the user to ef- ficiently test different setups, as well as interact and change the conditions during the simulation. The graphics card is used to generate additional frames for real-time visualization. This work further proposes a method for controlling and directing high resolution simulations. An interactive coarse resolution simulation is provided to the user as a “preview” to control and achieve the desired simulation behavior. A higher resolution “final” simulation that creates all the fine scale behavior is matched to the preview simulation such that the preview and final simulations behave in a similar manner. In this dissertation, we highlighted a gap within the CG community for the simulation of fire. There has not previously been a physically based yet interactive simulation for fire. This dissertation describes a unified simulation framework for physically based simulation of fire and burning. Our results show that our implementation can model fire, objects catching fire, burning objects, decomposition of burning objects, and additional secondary deformations. The results are plausible even at interactive frame rates, and controllable

3D-Modellierung mit interaktiven Oberflächen

3D models are at the core of many important applications from industry, science, and also entertainment. The creation of 3D models is a complex and time consuming process. Current modeling tools are hard to learn and require a deep understanding of the underlying mathematical models. Furthermore, established input devices like the mouse and keyboard do not utilize the full interaction potential -- especially regarding bimanual control -- of the human hand. The growing interest and the commercial breakthrough of multi-touch displays and interactive surfaces raises questions about their potential in the context of 3d modeling, which are thoroughly discussed and evaluated in this work. The presented approach is closely aligned to the whole processing chain for multi-touch applications, starting with the hardware and tracking issues, continuing with fundamental design discussions and operations like selection and 3D manipulation of objects and finishing with complex modeling techniques and metaphors. In regard to hardware and tracking, a robust illumination setup for the diffuse illumination technique is presented along with two extensions of this approach, i.e., hover detection and hand distinction. The design space is organized into specific design dimensions characterized by extremal positions to allow a better overview of design choices and a classification of existing and future systems. Fundamental techniques for selection and integrated 3D manipulation with six degrees of freedom are presented and empirically evaluated. Finally, two established modeling techniques -- implicit surfaces and virtual sculpting -- are extended and evaluated for multi-touch input

An efficient active B-spline/nurbs model for virtual sculpting

This thesis presents an Efficient Active B-Spline/Nurbs Model for Virtual Sculpting. In spite of the on-going rapid development of computer graphics and computer-aided design tools, 3D graphics designers still rely on non-intuitive modelling procedures for the creation and manipulation of freeform virtual content. The ’Virtual Sculpting' paradigm is a well-established mechanism for shielding designers from the complex mathematics that underpin freeform shape design. The premise is to emulate familiar elements of traditional clay sculpting within the virtual design environment. Purely geometric techniques can mimic some physical properties. More exact energy-based approaches struggle to do so at interactive rates. This thesis establishes a unified approach for the representation of physically aware, energy-based, deformable models, across the domains of Computer Graphics, Computer-Aided Design and Computer Vision, and formalises the theoretical relationships between them. A novel reformulation of the computer vision approach of Active Contour Models (ACMs) is proposed for the domain of Virtual Sculpting. The proposed ACM-based model offers novel interaction behaviours and captures a compromise between purely geometric and more exact energy-based approaches, facilitating physically plausible results at interactive rates. Predefined shape primitives provide features of interest, acting like sculpting tools such that the overall deformation of an Active Surface Model is analogous to traditional clay modelling. The thesis develops a custom-approach to provide full support for B-Splines, the de facto standard industry representation of freeform surfaces, which have not previously benefited from the seamless embodiment of a true Virtual Sculpting metaphor. A novel generalised computationally efficient mathematical framework for the energy minimisation of an Active B-Spline Surface is established. The resulting algorithm is shown to significantly reduce computation times and has broader applications across the domains of Computer-Aided Design, Computer Graphics, and Computer Vision. A prototype ’Virtual Sculpting’ environment encapsulating each of the outlined approaches is presented that demonstrates their effectiveness towards addressing the long-standing need for a computationally efficient and intuitive solution to the problem of interactive computer-based freeform shape design

A HYBRID ORIGIN: re-thinking computer aided design through hand-printing clay

In A Hybrid Origin, the coiled vessel is thought of as the source of 3D printing. The meditative coiling state, which I define as hand-printing clay is an instrument to think through ideas relating to my wider sculptural practice. It has now transformed into a hybridised version of learnt printing patterns and observations taken from computer aided design, mesh editing, and 3D slicing software. This software’ is understood through a heightened sense of movement and material awareness that has been influenced by my interaction with clay and digital fabrication techniques. I take the position that there is a systemic problem within the processes of computer aided design (CAD) for expressive practitioners who place importance on a physical material connection. Formal decisions are being made more and more by computer programs with little to no material origin. My sculptural practice requires a conduit between the different processes involved within CAD and 3D printing, so that the physical experience of hand-printing clay (HPC) can be better digitally expressed. Examples of this Hybrid Origin are enacted in a series of practical projects that are recorded and manipulated in different ways, using varying computational platforms and electronic sensory conduits. My research questions examine hybrid movements towards a sensitivity in digital objects via HPC, CAD, and other satellite computer-based design programs. The fields of Fine Art, Fabrication, Design, Architecture, Craft and Human-Computer-Interaction can benefit from this research with cross overs occurring in many other academic disciplines which gives practical examples of integrating varying levels of hand making into the space of CAD and the 3D printing workflow. It offers contributions that change the direction of travel for CAD: not originating from a desk-based beginning, but with a connection to the material and labour that is essential in bringing something physical into the world. It enables a connection we need to get back, that promotes care and offers a new way of designing into computers that uses material as origin