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Geometric Approximations Towards Free Specular Comic Shading
Holger Winnemöller, Shaun Bangay.
Computer Graphics Forum (EG'02),
2002. [BibTeX]
Implementing Non-photorealistic Rendering Enhancements with Real-Time Performance
Holger Winnemöller.
Computer Science Department, Rhodes University, February,
2002. [BibTeX]
Perceptually-motivated Non-Photorealistic Graphics
Holger Winnemöller.
Northwestern University, Evanston, Illinois, U.S.A.,
2006. [BibTeX]
Real-Time Video Abstraction
Author(s): Holger Winnemöller, Sven C. Olsen, Bruce Gooch.
Article: ACM Transactions on Graphics (Proc. of SIGGRAPH'06), Vol. 25, No. 3, pp. 1221--1226, July,
2006.
[BibTeX] [DOI] 
Abstract:
We present an automatic, real-time video and image abstraction framework that abstracts imagery by modifying the contrast of visually important features, namely luminance and color opponency. We reduce contrast in low-contrast regions using an approximation to anisotropic diffusion, and artificially increase contrast in higher contrast regions with difference-of-Gaussian edges. The abstraction step is extensible and allows for artistic or data-driven control. Abstracted images can optionally be stylized using soft color quantization to create cartoon-like effects with good temporal coherence. Our framework design is highly parallel, allowing for a GPU-based, real-time implementation. We evaluate the effectiveness of our abstraction framework with a user-study and find that participants are faster at naming abstracted faces of known persons compared to photographs. Participants are also better at remembering abstracted images of arbitrary scenes in a memory task.
Rendering optimisations for stylised sketching
Holger Winnemöller, Shaun Bangay.
2nd International Conference on Computer Graphics, Virtual Reality and Visualisation in Africa (AFRIGRAPH'03), pp. 117--122, Cape Town, South Africa,
2003. [BibTeX]