Non-Photorealistic Computer Graphics Library

Stroke Surfaces: A Spatio-temporal Framework for Temporally Coherent Non-photorealistic Animations

Author(s): John P. Collomosse, D. Rowntree, Peter M. Hall.
Technical Report: University of Bath, No. CSBU 2003-01, June, 2003.
[BibTeX]

Abstract:
We present a novel framework for the automated synthesis of non-photorealistic animations from video sequences. Our approach is unique in that we interpret the source video sequence as a spatio-temporal voxel volume, with time as the third dimension. Video frames are segmented into homogeneous regions, and heuristic associations between regions formed over time to produce a collection of conceptually high level spatio-temporal objects. These objects carve sub-volumes through the video volume delimited by continuous isosurface ``Stroke Surface'' patches. By manipulating objects in this representation we are able to synthesise a wide gamut of artistic effects, which we allow the user to stylise and influence through a parameterised ``Video Paintbox''. In addition to novel temporal effects unique to our method we demonstrate the extension of `traditional' static NPR styles to video including painterly, sketchy and 'toon shading effects. An application to advanced rotoscoping is also identified. The high level of analysis afforded by our spatio-temporal approach allows us to maintain a high degree of temporal coherence; a property scarce in current NPR video techniques which process video at a low level (on a per pixel, per frame sequential basis). The paper concludes with a critical appraisal and discussion of future applications for the Stroke Surface representation, including potential for video compression.