Pauline Jepp

Sketching, scaffolding, and inking: a visual history for interactive 3D modeling

Inspired by the comic-book production pipeline, a method is proposed for integrating visual aspects of the sketching process into 3D sketch-based modeling systems. In particular, artist-drawn construction aids called visual scaffolding are explored. Two scaffolding components which simulate elements of pencil sketching, geometric massing and eraser marks, are integrated into a rendering pipeline which also includes a suite of new object-space techniques for high-fidelity pen-and-ink depiction of implicit surfaces. Based on a hybrid, hierarchical approach which leverages both the implicit surface definition and an underlying coarse tessellation, new methods are described for computing silhouettes, suggestive contours, surface stippling, and surfel-based visibility culling. These techniques are real-time but require no pre-computation, allowing them to be applied to dynamic hierarchical implicit surfaces, and are demonstrated in ShapeShop, an interactive sketch-based modeling tool. The result is a real-time display pipeline which composites these novel scaffolding and pen-and-ink techniques to depict a visual history of the modeling process.

Pen-and-Ink for BlobTree Implicit Models

We present new techniques for rendering hierarchical, skeletal implicit models in several pen-and-ink styles. Our approach extracts silhouette strokes and lines following local shape features, such as those caused by CSG junctions. To this end, it uses particle systems to find interesting areas on the surface and perform stroke stylization guided by local shape features. Also, it removes hidden lines either by applying a surfel technique for rapid prototyping, or more accurately by using ray tracing. Examples from simple to complex models illustrate the capabilities of our system.

Sketch based construction and rendering of implicit models

We present an implicit modeling system as a tool for creating a wide range of aesthetic models. Because of their ability to form blends and produce both organic shapes as well as man-made objects, implicit surfaces are a good medium for artists seeking new ways to experiment with 3D modeling. Implicit models can be created using our sketch-based modeling tool Shapeshop and also by using a procedural interface. Further, we exploit the differential properties of implicit surfaces to explore new techniques for rendering hierarchical, skeletal implicit models in several pen and ink styles. Our method extracts and stylizes silhouette strokes, lines following local shape features, such as those caused by CSG junctions and abrupt blends, and short interior marks to reveal basic form. In this approach we use a particle system as a basis for the stroke extraction method.

A Survey on Implicit Surface Polygonization

Implicit surfaces (IS) are commonly used in image creation, modeling environments, modeling objects, and scientific data visualization. In this article, we present a survey of different techniques for fast visualization of IS. The main classes of visualization algorithms are identified along with the advantages of each in the context of the different types of IS commonly used in computer graphics. We focus closely on polygonization methods, as they are the most suited to fast visualization. Classification and comparison of existing approaches are presented using criteria extracted from current research. This enables the identification of the best strategies according to the number of specific requirements, such as speed, accuracy, quality, or stylization.

An Agent Framework for a Modular Serious Game

The architecture described in this paper provides emotional, believable agents for a serious game environment. Agents are designed to help players learn skills and to evaluate performance. The framework has been designed with a close connection to the development of other system components: the Game Engine for creating the virtual world; the Narrative Engine for driving the story; and the Dialogue System for communication. In order to provide a synchronized, intelligent solution it is essential to adapt traditional designs for independent components to consider the system as a whole. Effective communication and synchronization between system components is created by introducing a new system element: the Translation Engine. In this paper we describe the Agent Framework and associated services within the Translation Engine. This includes communication to other relevant system components but the components themselves are treated as black boxes.

Using Multi-agent Systems for Sampling and Rendering Implicit Surfaces

In this paper a multi-agent system for sampling and rendering implicit surfaces is presented (MASSRIS). Previous approaches to pen-and-ink style renderings of implicit surfaces were based on particle systems, which, for a complex surface, are slow to achieve a good distribution of particles and subsequently to trace features. The method proposed in this research extends traditional particles into semi-autonomous agents that sample the implicit model and illustrate surface features. Agents use goal directed behaviors to achieve a good coverage of surface strokes and feature outline identification faster than with previous particle-based methods.

Subdivision Surfaces for Fast Approximate Implicit Polygonization

We propose a fast method of generating an approximate polygonal mesh from an implicit surface. Current workstations are still not capable of producing polygon meshes fast enough for the interactive modelling of complex implicit models. We propose a hybrid method that combines current implicit polygonization techniques with the faster sub-division surface technique applied as a post-process to smooth the implicit mesh. In an interactive enviroment the smooth mesh points can be migrated to the implicit surface, in idle moments when the user is not interacting with the model. The technique can be further enhanced by providing tools for the user to indicate areas of interest that can be preferentially smoothed.

Style nodes and repolygonization for hierarchical tree-based implicit surface modelling

In this paper we present an extension to a hierarchical tree based implicit surface modelling system that includes interactively controlling style and appearance, and also creating a more accurate curvature based polygonal approximation. Multiple styles can be layered and applied to objects so that they are guided by local geometry although not strictly bound by it. To achieve this a new node, the Style Unary Node, is added to the ShapeShop BlobTree, which creates a style blending region inspired by primitive field blending. As visualization of implicit surfaces in interactive environments is often based on polygonization a more accurate curvature based polygonisation algorithm is also presented.

Implicit Modeling with Skeleton Curves: Controlled Blending in Contact Situations

Interactive implicit modelling with complex skeletons was recently improved with the introduction of primitives defined at different LODs. These implicit primitives use a subdivision curve as a skeleton. In this paper an extension to this representation is presented, in order to make it suitable for the interactive modelling and animation of soft objects in contact situations. The first contribution improves the display method for subdivision-based implicit primitives; this uses an adaptive polygonisation which locally refines, where necessary, according to the currently selected LOD. The second contribution consists of a new method for preventing unwanted blending when a skeleton-curve folds back onto itself. The third introduces local deformations where surfaces that should not blend come into contact. We illustrate the benefits of this methodology by describing two applications: the interactive modelling of complex organic shapes in contact situations and the physically-based animation of such organic shapes.