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Item Using The Barnes-Hut Approximation for Fast N-Body Simulations in Computer Graphics(The Eurographics Association, 2023) Dravecky, Peter; Stephenson, Ian; Vangorp, Peter; Hunter, DavidParticle systems in CG often encounter performance issues when all the particles rely on mutual influence, producing an O(N2) performance. The Barnes-Hut approximation is used in the field of astrophysics to provide sufficiently accurate results in O(Nlog(N)) time. Here we explore a hardware accelerated implementation of this algorithm, implemented within SideFX Houdini - the commercial tool typically used for particle work in film. We are able to demonstrate a workflow with integrates into the existing artist friendly environment, with performance improved by orders of magnitudes for typically large simulations, and negligible visual change in results.Item Interactive Relighting for Stage Use(The Eurographics Association, 2009) Stephenson, Ian; Wen Tang and John CollomosseRe-lighting by combining images taken under known lighting conditions to synthesise new lighting configurations is a simple, but powerful technique capable of producing impressive results. However it has found little practical application. Here we demonstrate the integration of a relighting tool into a typical theatrical lighting system, to provide real time previews both offline when the stage is unavailable, and during performance.Item Hardware Accelerated Shaders Using FPGAs(The Eurographics Association, 2009) Goddard, Luke; Stephenson, Ian; Wen Tang and John CollomosseWe demonstrate that Field Programable Gate Arrays (FPGAs) can be used to accelerate shading of surfaces for production quality rendering (a task standard interactive graphics hardware is generally ill-suited to) by allowing circuits to be dynamically created at run-time on standard commercial logic boards. By compiling shaders to hardware descriptions, they can be executed on FPGA with the performance of hardware without sacrificing the flexibility of software implementations. The resulting circuits are fully pipelined, and for circuits within the capacity of the FPGA can shade MicroPolygons at a fixed rate independent of shader complexity.Item A Desktop Multi-Touch Interface for Posing Characters(The Eurographics Association, 2011) Stephenson, Ian; Ian Grimstead and Hamish CarrMulti-touch, direct manipulation interfaces have become common in mobile media applications, but their use on the desktop is limited. In this paper we propose that multi touch direct manipulation is well suited to the posing of animated characters using inverse kinematics, and demonstrate how it can be implemented in a desktop application, by the addition of commodity mobile touch devices. We also describe how the multi-touch display software developed for this system can be integrated into a number of other applications.Item Screen Space Re-Rendering for the Simulation of Concert Lighting(The Eurographics Association, 2010) Stephenson, Ian; Scanlan, Liam; John Collomosse and Ian GrimsteadThe visualisation of modern concert lighting requires complex illumination models to be calculated at interactive frame rates. Each light may have 20 or more parameters which are all changing in real time. Here we present a technique which allows static scenes with rapidly changing illumination to be re-rendered quickly in graphics hardware, with support for arbitrary geometry, complex BRDFs, shadowing and volumetric fogging. The rendering algorithm is re-factored to allow changing lighting to be applied to scenes which are otherwise fully rendered, minimising the calculation required when lights are moved.Item Computer Modelling of Theatrical Sets(The Eurographics Association, 2010) Stephenson, Ian; Pride, Rebecca; John Collomosse and Ian GrimsteadHere we discuss the design and implementation of a modelling tool specifically targeted for use by designers of theatrical sets. By applying domain specific knowledge and contraints to the design of the software, we demonstrate a system which can be used without signifigant training, by users with no previous computer graphics experience. We present initial end user experiences of using the tool in designing a real production of The First Arabian Night .