Approach Outline

1. CPU implementation Performance scales almost linearly with the number of processors/cores. Additional optimization techniques can be used to accelerate model evaluation: - employing time coherence (avoiding unnecessary evaluations outside zones of interest) - skipping surface extraction between certain frames - using faster function approximation GPU implementation Task is easily parallelized due to independent function evaluations in the volume. Function evaluation, mesh extraction and rendering performed entirely on the GPU. Current implementation is based on CUDA. Our technique can be implemented using DirectX or OpenGL, provided that geometry shaders are available. Results References [Kravtsov08] Kravtsov, D., Fryazinov, O., Adzhiev, V., Pasko, A., Comninos, P., “Embedded Implicit Stand-ins for Animated Meshes: a Case of Hybrid Modelling”. Technical report. The National Centre for Computer Animation, Bournemouth University, UK, 2008 [Pasko95] Pasko, A., Adzhiev, V., Sourin, A., Savchenko, V., 1995. "Function representation in geometric modeling: concepts, implementation and applications", The Visual Computer, vol.11, No.8, 1995, pp.429-446. [Sherstyuk99] McCormack, J., Sherstyuk, A. “Creating and Rendering Convolution Surfaces”, Computer Graphics Forum”17 (2), 1998, pp. 113-120.s Advantages • Effects hardly achievable with pure polygonal models • Automatic geometric LOD due to resolution independence of the FRep model • Scalability • Easy integration into existing pipelines with intuitive control • Large number of potential applications (user generated content, new special effects, advanced interactions with environment etc) Polygonal-Functional Hybrids for Computer Animation and Games NCCA National Centre for Computer Animation, UK D. Kravtsov*, O. Fryazinov, V. Adzhiev, A. Pasko and P. Comninos *dkravtsov @ bmth.ac.uk Abstract Approach Outline Implementation • The modern world of computer graphics is mostly dominated by polygonal models. Due to their scalability and ease of rendering such models have various applications in a wide range of fields. Unfortunately some shape modelling and animation problems can hardly be overcome using polygonal models only. For example, dramatic changes of the shape (involving change of topology) or metamorphosis between different shapes can not be performed easily. The Function Representation (FRep) [Pasko95] allows us to overcome some of the problems and simplify the process of the major model modification. Our system is based on a hybrid modelling concept, where polygonal and FRep models are combined together and can be evaluated in near-real or real time [Kravtsov08]. It allows us to: • produce animations involving dramatic changes of the shape (e.g. metamorphosis, mimicking viscoelastic behaviour, character modifications etc) in short times • integrate existing animated polygonal models and FRep models within a single model • interactively create complex shapes with changing topology and specified level of detail (LOD) 1. Initialization step Maya™ plug-in A. Generate FRep model approximating the mesh, either “embedding” or “attaching” FRep model to the mesh We have implemented the proposed approach as a plug-in for Maya™. Our plug-in requires the user to specify both the skeletons and polygonal meshes, which are used to calculate the initial parameters of all the skeletal primitives of the convolution surface. Intermediate results of the implicit surface polygonization can be seen in the editor window in near real-time. Each parameter can be animated over time B. Synchronize skeletons for polygonal model and functional model Mesh Skeleton approximation thus providing the user with more flexibility to produce various effects. Attachment Embedding Attachment Embedding 2. Process Related Work Update parameters Update skeleton We use convolution surfaces [Sherstyuk99] to approximate an animated mesh. This type of implicit surfaces is easy to manipulate using an underlying lower dimensional skeleton and can be blended with each other smoothly. Resulting surface can be blended with any FRep object using blending union [Pasko95]. Evaluate scalar field produced by the “object” Evaluate scalar field produced by the skeleton Deform polygonal model Combine scalar fields No blending Blending union with varying parameters Extract polygons from combined scalar field Combine models