Title:	Non-pohotorealistic shape cues for visualisation
Authors:	Hall, Peter
Citation:	Journal of WSCG. 1995, vol. 3, no. 1-2, p. 113-122.
Issue Date:	1995
Publisher:	Václav Skala - UNION Agency
Document type:	článek article
URI:	http://wscg.zcu.cz/wscg1995/wscg95.htm http://hdl.handle.net/11025/16024
ISSN:	1213-6972 (print) 1213-6980 (CD-ROM) 1213-6964 (online)
Keywords:	vizualizace aplikací;modelování;model se strukturovaným osvětlením
Keywords in different language:	visualisation applications;modelling;model with structured lighting
Abstract in different language:	Visualisation applications often need to display objects that are both three dismensional and coloured. The objects may be represented either by surfaces or by volumes. The motivation behind such displays is to demonstrate two or more independent variables at once. So one variable may determine object shape and another variable may determine the distribution of colour. A lighting model is need to provides cues for visual shape recognition. Conventional lighting models provide these cues by altering colour, Hence a conflict arises when this approach is adopted because the total colour variation is made up of two components that are perceptually indistinguishable. There are variations that show the distribution of a variable, and global variations caused by the lighting model. It might be said that a side effect of the light model is to distort the information represented by colour. This paper offers a solution to this problem be replacing the conventional lighting model with a structured lighting model of the kind used in machine vision contexts. The proposed solution simulates the shadow of a regular, planar, grid on the surface of an object. Improved shape cues can be obtained by using a grid that is sensitive to lighting conditions, this generates a cross-hatch shading effect. The notion of a planar grid easily generalises to three dimensions, where it can be used not only with surfaces, but also with volumes. The benefit of the method is that colour is effected only locally, and in well defined places; the remaining colour is readily identifiable and faithfully represents underlying data. In addition, the method in either of its forms is simple to incorporate into existing renderers. The method is demostrated with results obtained from a computational fluid dynamics application. Both coloured iso-surfaces and coloured volumes are shown.
Rights:	© Václav Skala - UNION Agency
Appears in Collections:	Volume 3, number 1-2 (1995)

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