Embedded Implicit Stand-ins for Animated Meshes: a Case of Hybrid Modelling

In this paper we address shape modelling problems, encountered in computer animation and computer games development that are difficult to solve just using polygonal meshes. Our approach is based on a hybrid modelling concept that combines polygonal meshes with implicit surfaces. A hybrid model consists of an animated polygonal mesh and an approximation of this mesh by a convolution surface stand-in that is embedded within it or is attached to it. The motions of both objects are synchronised using a rigging skeleton. This approach is used to model the interaction between an animated mesh object and a viscoelastic substance, normally modelled in implicit form. The adhesive behaviour of the viscous object is modelled using geometric blending operations on the corresponding implicit surfaces. Another application of this approach is the creation of metamorphosing implicit surface parts that are attached to an animated mesh. A prototype implementation of the proposed approach and several examples of modelling and animation with near real-time preview times are presented

Modelling of the Complex CASSOWARY/SLUGS Gravitational Lenses

We present the first high-resolution images of CSWA 31, a gravitational lens system observed as part of the SLUGS (Sloan Lenses Unravelled by Gemini Studies) program. These systems exhibit complex image structure with the potential to strongly constrain the mass distribution of the massive lens galaxies, as well as the complex morphology of the sources. In this paper, we describe the strategy used to reconstruct the unlensed source profile and the lens galaxy mass profiles. We introduce a prior distribution over multi-wavelength sources that is realistic as a representation of our knowledge about the surface brightness profiles of galaxies and groups of galaxies. To carry out the inference computationally, we use Diffusive Nested Sampling, an efficient variant of Nested Sampling that uses Markov Chain Monte Carlo (MCMC) to sample the complex posterior distributions and compute the normalising constant. We demonstrate the efficacy of this approach with the reconstruction of the group-group gravitational lens system CSWA 31, finding the source to be composed of five merging spiral galaxies magnified by a factor of 13.Comment: Accepted for publication in MNRA

Winter tears: a study in computer animation

This project is a study into the art and science of Animation. Specifically, this project focuses on the development of story and character through the use of Computer Animation. From beginning to end, this animation comprises work done completely by the author. The main goal of the project was to understand the development process of an animated short through concentration on Story Development, Character Creation, and Character Animation. In totality, the completed work comprises 10 months of individual labor that began in July 2001 and ended in April 2002. These 10 months of work have resulted in the creation of a 5 minute animated short entitled Winter Tears. The spirit of the work was devoted towards expanding, testing, and solidifying the skill of the author. What has followed this long process is the best work that the author has produced to date. The process of the project was a constant struggle of both work and discovery. In addition to the primary goals, secondary goals were included. The first of these goals was the learning of an industry standard computer animation package called AliasWaveFrontMaya and the second the creation of an animation piece to be used in a portfolio for job applications. What the author hopes will be seen is a true love of animation and a profound respect for the amount of work and detail required for any animated piece in any discipline

Progressive refinement rendering of implicit surfaces

The visualisation of implicit surfaces can be an inefficient task when such surfaces are complex and highly detailed. Visualising a surface by first converting it to a polygon mesh may lead to an excessive polygon count. Visualising a surface by direct ray casting is often a slow procedure. In this paper we present a progressive refinement renderer for implicit surfaces that are Lipschitz continuous. The renderer first displays a low resolution estimate of what the final image is going to be and, as the computation progresses, increases the quality of this estimate at an interactive frame rate. This renderer provides a quick previewing facility that significantly reduces the design cycle of a new and complex implicit surface. The renderer is also capable of completing an image faster than a conventional implicit surface rendering algorithm based on ray casting

A Rigging Convention for Isosurface-Based Characters

This thesis presents a prototype system for generating animation control systems for isosurface-based characters that blurs the distinction between a skeletal rig and a particle system. Managing articulation and deformation set-up can be challenging for amorphous characters whose surface shape is defined at render time and can only be viewed as an approximation during the process of defining an animation performance. This prototype system utilizes conventional scripted techniques for defining animation control systems integrated with a graphical user interface that provides art directable control over surface contour, shape and silhouette for isosurface-based characters. Once animated, these characters can be rendered using Rendermans RIBlobby implementation and provide visual feedback of fluid motion tests. The prototype system fits naturally within common practices in digital character setup and provides the animator control over isosurface-based characters

Voxelisation in the 3-D Fly Algorithm for PET

International audienceThe Fly Algorithm was initially developed for 3-D robot vision applications. It consists in solving the inverse problem of shape reconstruction from projections by evolving a population of 3-D points in space (the 'flies'), using an evolutionary optimisation strategy. Here, in its version dedicated to tomographic reconstruction in medical imaging, the flies are mimicking radioactive photon sources. Evolution is controlled using a fitness function based on the discrepancy of the projections simulated by the flies with the actual pattern received by the sensors. The reconstructed radioactive concentration is derived from the population of flies, i.e. a collection of points in the 3-D Euclidean space, after convergence. 'Good' flies were previously binned into voxels. In this paper, we study which flies to include in the final solution and how this information can be sampled to provide more accurate datasets in a reduced computation time. We investigate the use of density fields, based on Metaballs and on Gaussian functions respectively, to obtain a realistic output. The spread of each Gaussian kernel is modulated in function of the corresponding fly fitness. The resulting volumes are compared with previous work in terms of normalised-cross correlation. In our test-cases, data fidelity increases by more than 10% when density fields are used instead of binning. Our method also provides reconstructions comparable to those obtained using well-established techniques used in medicine (filtered back-projection and ordered subset expectation-maximisation)

Implicit surfaces for interactive animated characters

Thesis (S.M.)--Massachusetts Institute of Technology, Program in Media Arts & Sciences, 1999.Includes bibliographical references (leaves 64-68).Implicit surface modeling in computer graphics is a powerful technique for representing smooth and organic shapes. Skeletal elements of an implicit surface blend to create a smooth, seamless skin which exhibits desired properties for animation such as squash and stretch. Because of their high computational cost to render, implicit surfaces have not been used extensively in the real-time graphics domain. This thesis discusses the problems and some solutions in the application of implicit surfaces to the domain of interactive character animation. A design process for an implicit surface-based character is proposed, from the modeling and texturing stages to animation and rendering.by Kenneth Bradley Russell.S.M

Creation of modular 3D assets for videogames

Hráči počítačových her mají stále vyšší a vyšší nároky na grafické zpracování herního světa a jeho detaily. Aby jim mohlo být vyhověno, grafici musí neustále upravovat svůj přístup a používané modelovací techniky. Jeden z moderních a populárních přístupů je založen na modularitě a modulárním designu. Přestože tento přístup má spoustu benefitů, přesný popis technik a znalostí spojených s tímto konceptem není stále pevně definovaný. Tato práce poskytuje náhled na různé modelovací techniky, software pro 3D modelování a detailní popis modulárního přístupu aplikovaného v aktuálních počítačových hrách. Kombinací procedurálních modelovacích technik a modulárního designu jsme v programu Houdini připravili několik assetů už pouze čekajících na reálné využití. Dále jsme v Unreal Enginu poskládali testovací scénu a tím získali hlubší přehled o výhodách a nevýhodách použitého přístupu k tvorbě grafiky počítačových her.In order to keep up with the ever-increasing player's demand for higher visual fidelity of game environments, artists are continually implementing new modelling techniques and production methods into their workflow. One popular contemporary approach that has emerged is based on the notion of modular design. Although it offers many benefits for production workflow, the particular techniques and skills associated with this concept are still not well defined. This thesis provides an overview of various modelling techniques, 3D modelling software and thorough discussion of the modular design paradigm applied in computer games. We have combined procedural modelling techniques with the concept of modular design to create several game-ready assets in Houdini. We then assembled a simple test scene in Unreal Engine in order to gain a more in-depth insight into the advantages and disadvantages of the discussed workflow