Apparent relief: a shape descriptor for stylized shading

Shape depiction in non-photorealistic rendering of 3D objects has mainly been concerned with the extraction of contour lines, which are generally detected by tracking the discontinuities of a given set of shape features varying on the surface and/or the picture plane. In this paper, we investigate another approach: the depiction of shape through shading. This technique is often used in scientific illustration, comics, cartoon animation and various other artwork. A common method consists in indirectly adapting light positions to reveal shape features; but it quickly becomes impractical when the complexity of the object augments. In contrast, our approach is to directly extract a set of shape cues that are easily manipulated by a user and re-introduced during shading. The main problem raised by such an approach is that shape cues must be identified in a continuous way in image space, as opposed to line-based techniques. Our solution is a novel view-dependent shape descriptor called Apparent Relief, which carries pertinent continuous shape cues for every pixel of an image. It consists of a combination of object- and image-space attributes. Such an approach provides appealing properties: it is simple to manipulate by a user, may be applied to a vast range of styles, and naturally brings levels-of-detail functionalities. It is also simple to implement, and works in real-time on modern graphics hardware.

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Graphics [cs.GR]

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minimal2.png (161.01 Ko)

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xShade1Convex.png (298 Ko)

xShade2Concav.png (271.1 Ko)

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https://inria.hal.science/inria-00277084

Submitted on : Sunday, October 27, 2013-12:01:19 PM

Last modification on : Thursday, February 15, 2024-3:32:35 AM

Long-term archiving on: Tuesday, January 28, 2014-4:32:16 AM

Dates and versions

inria-00277084 , version 1 (05-05-2008)

inria-00277084 , version 2 (27-10-2013)

Identifiers

HAL Id : inria-00277084 , version 2
DOI : 10.1145/1377980.1377987

Cite

Romain Vergne, Pascal Barla, Xavier Granier, Christophe Schlick. Apparent relief: a shape descriptor for stylized shading. NPAR '08: Proceedings of the 6th international symposium on Non-photorealistic animation and rendering, Jun 2008, Annecy, France. pp.23-29, ⟨10.1145/1377980.1377987⟩. ⟨inria-00277084v2⟩

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