Brian Wyvill - Academia.edu (original) (raw)

Papers by Brian Wyvill

Composition and Perception beyond Photorealism

Composition is an important aestheic aspect of celebrated works of art, and we examine a few comm... more Composition is an important aestheic aspect of celebrated works of art, and we examine a few common compositional techniques in the context of computer graphics rendering and perception. In computer graphics, photorealistic rendering simulates a camera, which defines an image of a scene in a single instant after the shutter is released. In contrast, a human observer looks at one part of a scene at a time and stitches a series of visual memories together to form a complete impression of the scene. This perception process is related to visual composition, in which an artist selectively articulates and suppresses details to direct the viewers' eyes. In non-photorealistic rendering research, painting is an important source of examples for stylized rendering. We discuss the importance of painting's specific presentation conditions, and how painting composition takes effect through a viewer's attentive looking. Based on these analysis, we demonstrate how to apply knowledge of composition to digital image synthesis with an interpolative material model and a staged photography art project.

By combining knowledge from computer graphics and visual arts, we have built a projection install... more By combining knowledge from computer graphics and visual arts, we have built a projection installation based on a novel sketch-based shape pattern rendering method. Our novel rendering method is guided by an artist's drawing, and generates shape patterns resembling the input image, creating animation with an organic appearance. We have also applied the proposed method to render foliage shadow effects for virtual scenes. The major contribution of method is its ability to automatically render richly detailed, animated lighting patterns from an approximate lighting plan drawing. In our research team, professional artists and computer graphics researchers work together to develop our rendering method and the artistic rendering projects side by side. This interdisciplinary approach helps us to design and evolve our method for creating aesthetic work with computer graphics technologies.

ACM Transactions on Graphics, 2014

We present a novel approach to interactive character skinning, which is robust to extreme charact... more We present a novel approach to interactive character skinning, which is robust to extreme character movements, handles skin contacts and produces the effect of skin elasticity (sliding). Our approach builds on the idea of implicit skinning in which the character is approximated by a 3D scalar field and mesh-vertices are appropriately re-projected. Instead of being bound by an initial skinning solution used to initialize the shape at each time step, we use the skin mesh to directly track iso-surfaces of the field over time. Technical problems are two-fold: firstly, all contact surfaces generated between skin parts should be captured as iso-surfaces of the implicit field; secondly, the tracking method should capture elastic skin effects when the joints bend, and as the character returns to its rest shape, so the skin must follow. Our solutions include: new composition operators enabling blending effects and local self-contact between implicit surfaces, as well as a tangential relaxati...

ACM Transactions on Graphics, Jul 12, 2019

Fabrication (FFF) technology, since most printers in this category can deposit along slightly cur... more Fabrication (FFF) technology, since most printers in this category can deposit along slightly curved paths, under deposition slope and thickness constraints. Our algorithm curves the layers, making them either follow the natural slope of the input surface or on the contrary, make them intersect the surfaces at a steeper angle thereby improving the sampling quality. Rather than directly computing curved layers, our algorithm optimizes for a deformation of the model which is then sliced with a standard planar approach. We demonstrate that this approach enables us to encode all fabrication constraints, including the guarantee of generating collision-free toolpaths, in a convex optimization that can be solved using a QP solver. We produce a variety of models and compare print quality between curved deposition and planar slicing. CCS Concepts: • Computing methodologies → Shape modeling.

Disruptions in Art, Science, Engineering and Modeling

Blockaid a Model for Program Execution

We illustrate a technique for picturing the dynamic behaviour of block structured programs under ... more We illustrate a technique for picturing the dynamic behaviour of block structured programs under execution. Examples are shown using Pascal programs but the method is perfectly general. It shows how procedures are incarnated when called and deleted on exit. A clear interpretation of the binding rule is given for local and global variables and parameters; and the need for multiple copies for recursively called procedures is demonstrated.

Animation in Warped Space

Free form deformations are useful for describing a class of complex motions within an animation s... more Free form deformations are useful for describing a class of complex motions within an animation system. Such deformations have been described using a generalization of parametric surfaces and their application to modeling is well documented. In this paper we present a method that can be applied to implicit surfaces which are defined as an iso-surface around a set of skeletal elements, contributing to a scalar field. The resulting surface is approximated by a polygon mesh. Shape distortions, such as "squash and stretch" are applied automatically to models in motion by warping the space in which the models exist. A model will change its shape as the function defining the warped space can change over time or, the model will deform as it moves through the warped space. Sophisticated, possibly non-linear deformations can be achieved on arbitrarily complex surfaces. Several examples are given including a running wave simulation and a slug like creature. The interesting, non-linear motion obtained, from space warping would be difficult to reproduce using other techniques.

With the increased complexity in state of the art models created using common digital content cre... more With the increased complexity in state of the art models created using common digital content creation applications, such as AutoCAD, Maya or XSI, the need to have more than one person work on a single model is common. Ideally people would work on the same model at the same time, from several workstations possibly at distant locations. Using a mesh based modelling approach requires synchronizing thousands of triangles over the network between all participating workstations. In contrast the BlobTree is based on combining skeletal primitives using standard CSG and various blending operators. Using this methodology complex models can be encoded with a smaller memory footprint than mesh based systems, thus allowing for less traffic across a network to synchronize two or more workstations with one model. In this paper we propose a network protocol to allow collaborative, sketch-based implicit modelling using the BlobTree.

Many of the most interesting behaviors in the biological world have to do with interactions betwe... more Many of the most interesting behaviors in the biological world have to do with interactions between species. The predator-prey interactions among aquatic organisms is an interesting part of the natural world which has not been seen much in computer animation. This paper explores the interaction between various sea anemones and the starfish Dermasterias imbricata. Although a simulation between a specific sea anemone, Stomphia coccinea to Dermasterias imbricata was created, an approach was taken such that different anemones can with minor parameter changes be used to replace S. coccinea. The animation was created using a parametric keyframe approach of procedural models. The anemone and starfish were modeled using the BlobTree. The implicit model within the system is defined as a hierarchical composition of multiple objects. Using a hierarchical construction of the model, we can refine the model locally and deform it globally while maintaining the integrity of surface details.

Visualising a Simulation Using Animated Pictures

We examine an application of Jaggies, a 2D graphics system designed as part of the Jade software ... more We examine an application of Jaggies, a 2D graphics system designed as part of the Jade software prototyping environment. The Jade research project is aimed at building an environment which comfortably supports the design, construction, and testing of distributed computer systems. Jaggies is based on a hierarchical data structure and avoids storage of large picture files. In this application, Jaggies provides versatile support for the graphical display of the state of the Andes simulation interpreter. Jaggies pictures are represented as linked lists of objects. An object describes an instance of a picture or a primitive. The Jaggies data structure is accessed via a set of procedures which may be called from an application program. Some of the more unusual features of Jaggies are: the system maintains an internal model of the display which may be altered incrementally; the system may be distributed across several processors; and recursively structured pictures may be defined. In Andes a simulation running on a host machine communicates with one or more Jaggies programs running on a Jade graphics workstation using Jade Inter Process Communication (JIPC). The user first goes through a design phase in which graphical icons are defined to represent specific entities in the simulation. These icons are represented in a compact form as a Jaggies data structure which resides on the workstation. Simple real-time animation functions may also be specified. As the simulation progresses the icons appear when entities are created and move in accordance with commands from the simulation program. The user may interact with the graphics; for example, different views may be created and areas of interest may be re-scaled to show details. Andes is being implemented on a VAX/780 host machine and a Corvus Concept workstation.

Painting with flowsnakes

Space filling curves, invented by mathematicians in the 19th century, have long been a fascinatio... more Space filling curves, invented by mathematicians in the 19th century, have long been a fascination for artists, however there are no interactive tools to allow an artist to create and explore various levels of recursion of the curve in different parts of the artwork. In this work a new type of painting tool for artists is introduced, which gives the artist control over the very base of a space filling curve, i.e recursive subdivision. Although there are many such curves that would lend themselves to this treatment, the Flowsnake (Gosper) curve has been chosen in this work, mainly for its aesthetics. The curve is based on a hexagonal grid, and in our system hexagons are subdivided at the artist's touch in a non-homogeneous manner, leaving a trail that forms the space filling curve. Some tools are introduced for controlling the painting, such as limiting the depth of recursion, and the 'slow brush', which interpolates slowly between subdivisions to allow the artist to stop at a chosen level. A set of space filling curve brush types provide different shapes and profiles, for giving the artist control of the nonhomogeneous subdivision, including the ability to un-subdivide the hexagons. An algorithm for drawing the curve non-recursively is introduced in order to produce a polyline suitable for processing on the GPU to make the system function at interactive rates. An animated version of the image can be made by replaying the subdivisions from the first level. Some examples made by art students and graduates are shown, along with the artist's comments on the system.

Jade シミュレーションとソフトウエア・プロトタイピング環境

Natural Phenomenae-I: Static Modelling

Springer eBooks, 2009

An overview is presented of the use of spatial data structures in spatial databases. The focus is... more An overview is presented of the use of spatial data structures in spatial databases. The focus is on hierarchical data structures, including a number of variants of quadtrees, which sort the data with respect to the space occupied by it. Such t e c hniques are known as spatial indexing methods. Hierarchical data structures are based on the principle of recursive decomposition. They are attractive because they are compact and depending on the nature of the data they save space as well as time and also facilitate operations such as search. Examples are given of the use of these data structures in the representation of di erent data types such as regions, points, rectangles, lines, and volumes.

Eurographics Workshop on Parallel Graphics and Visualization, 2012

In this research we tackle the problem of rendering complex models which are created using implic... more In this research we tackle the problem of rendering complex models which are created using implicit primitives, blending operators, affine transformations and constructive solid geometry in a design environment that organizes all these in a scene graph data structure called BlobTree. We propose a fast, scalable, parallel polygonization algorithm for BlobTrees that takes advantage of multicore processors and SIMD optimization techniques available on modern architectures. Efficiency is achieved through the usage of spatial data structures and SIMD optimizations for BlobTree traversals and the computation of mesh vertices and other attributes. Our solution delivers interactive visualization for modeling systems based on BlobTree scene graph.

Implicit surface modeling systems have been used since the mid-1980's for the generation of carto... more Implicit surface modeling systems have been used since the mid-1980's for the generation of cartoon-like characters. Recently implicit models combined with constructive solid geometry (CSG) have been used to build engineering models with automatic blending. This work is based on a structured implicit modeling system which includes CSG, warping, 2D texture mapping and operations based on the BlobTree, and its application to the generation of a complex and visually accurate biological model of the sea shell Murex cabritii. Since the model is purely procedurally defined and does not rely on polygon mesh operations, it is resolution independent and can be rendered directly using ray tracing. An interface has been built for the BlobTree using an interpreted programming language (Python). The language interface readily allows a user to procedurally describe the shell based on numeric data taken from the actual object.

Computer Aided Design, 2016

h i g h l i g h t s • We show how to improve BlobTree traversal time by one order of magnitude. •... more h i g h l i g h t s • We show how to improve BlobTree traversal time by one order of magnitude. • We demonstrate how to incorporate Warp Transformations within the BlobTree into new traversal. • The performance is measured on computer generated and hand built models.

Soft objects for soft shadows

A framework for rule-based behavioural simulation in voxel space

This dissertation presents a framework for rule based behavioural simulation (FRBBS). This framew... more This dissertation presents a framework for rule based behavioural simulation (FRBBS). This framework is based on our structured understanding of the field of behavioural simulation. The important concepts, principles and application scope of behavioural simulation are identified and described in the dissertation. They are supported in FRBBS with an object oriented approach. A set of new techniques for behavioural simulation are developed in this dissertation. They include the methods for formal behaviour rule specification with TCCS, building specific behavioural systems from an abstract model, modeling reproduction for behavioural systems, and a mechanism to implement the environment, including actor-environment interaction, by using a voxel space representation. The rationale for using these techniques are explained. Several examples are presented and used in the evaluation of the ideas of this dissertation. Future research directions are also discussed.