The notion of quantitative invisibility and the machine rendering of solids

Appel, Arthur

doi:10.1145/800196.806007

Cited by 131 publications

(57 citation statements)

References 3 publications

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“…Such techniques include the use of visibility information [1,19] as well as the use of halos [2,11], the illustration method we also use in our own work. Halos, however, can not only be used in line rendering but have been applied in more traditional visualization techniques based, e. g., on line integral convolution [16] or volume rendering [5] to enhance depth perception.…”

Section: Illustrative Visualization and Rendering Techniquesmentioning

confidence: 99%

Depth-Dependent Halos: Illustrative Rendering of Dense Line Data

Everts

Bekker

Roerdink

et al. 2009

IEEE Trans. Visual. Comput. Graphics

111

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Abstract-We present a technique for the illustrative rendering of 3D line data at interactive frame rates. We create depth-dependent halos around lines to emphasize tight line bundles while less structured lines are de-emphasized. Moreover, the depth-dependent halos combined with depth cueing via line width attenuation increase depth perception, extending techniques from sparse line rendering to the illustrative visualization of dense line data. We demonstrate how the technique can be used, in particular, for illustrating DTI fiber tracts but also show examples from gas and fluid flow simulations and mathematics as well as describe how the technique extends to point data. We report on an informal evaluation of the illustrative DTI fiber tract visualizations with domain experts in neurosurgery and tractography who commented positively about the results and suggested a number of directions for future work.

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Section: Illustrative Visualization and Rendering Techniquesmentioning

confidence: 99%

Depth-Dependent Halos: Illustrative Rendering of Dense Line Data

Everts

Bekker

Roerdink

et al. 2009

IEEE Trans. Visual. Comput. Graphics

111

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“…Contour edges are those edges which separate frontfacing and backfacing polygons at those places where the surface curves behind itself or else edges which lie at the extremes of the surface, for surfaces which don't close on themselves [1]. Thus any area lying within the bounds of a set of contour edges for a single surface can be treated as a unit assuming that the bounded surface is the frontmost surface in the bounded area.…”

Section: A Second Class: the Two-pass Approachmentioning

confidence: 99%

“…The quantitative invisibility with respect to the light source (previously computed for all visible vertices) is then used to determine those segment parts which lie in shadow. Further detail is available in Appel's publications [1,2,3].…”

mentioning

confidence: 99%

Shadow algorithms for computer graphics

Crow

1977

SIGGRAPH Comput. Graph.

265

140

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Appel [3] and then Bouknight and Kelley [5] have demonstrated solutions to the shadow problem which are discussed in this paper in the context of a classification scheme for shadow algorithms. Three classes of solution are currently identifiable (there may be further undiscovered classes). Appel, Bouknight and Kelley have shown solutions of one class and algorithms suggesting the other two classes have been proposed but not yet implemented.The first class of algorithm, demonstrated by Appel, Bouknight and Kelley, detects shadow boundaries as the image is produced by a raster-scan. The edges of cast shadows are found by projecting potential shadowing polygon edges onto the surface being scanned. Shadow edges thus formed are then projected onto the image plane. Upon crossing a shadow edge, the color of a scan segment is changed appropriately.A second class of algorithm involves two passes through a hidden-surface algorithm, or perhaps a single pass through each of two differing algorithms. The first pass distinguishes shadowed and unshadowed surfaces and divides partially shadowed surfaces by determining hidden surfaces from a viewpoint coincident with the light source. The colors of shadowed surfaces are then modified and a second pass operates on the augmented data from the observer's viewpoint.The third class of shadow algorithm involves calculating the surface enclosing the volume of space swept out by the shadow of an object, its umbra. The umbra surface is then added to the data and treated as an invisible surface which, when pierced, causes a transition into or out of an object shadow.A more complete explanation of the three classes follows with suggested implementations in each class. These will be preceded by remarks on modeling of the light source and followed by an attempted comparison of the practical difficulties in implementing the three approaches. MODELING THE LIGHT SOURCELight sources are generally modeled as either points or directions. However, an actual light ABSTRACT Shadows are advocated for improved comprehension and enhanced realism in computer-synthesized images. A classification of shadow algorithms delineates three approaches: shadow computation during scanout; division of object surfaces into shadowed and unshadowed areas prior to removal of hidden surfaces; and inclusion of shadow volumes in the object data. The classes are related to existing shadow algorithms and implementations within each class are sketched. A brief comparison of the three approaches suggests that the last approach has the most appealing characteristics.

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“…Line visibility has been the subject of research since the 1960's. Appel [1967] introduced the notion of quantitative invisibility, and computed it by finding changes in visibility at certain (typically rare) locations. This approach was further improved and adapted to NPR by Markosian et al [1997] who showed it could be performed at interactive frame rates for models of modest complexity.…”

Section: Background and Related Workmentioning

confidence: 99%

Fast high-quality line visibility

Cole

Finkelstein

2009

Proceedings of the 2009 Symposium on Interactive 3D Graphics and Games

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Figure 1: Examples of models rendered with stylized lines. Stylized lines can provide extra information with texture and shape, and are more aesthetically appealing than conventional solid or stippled lines. AbstractLines drawn over or in place of shaded 3D models can often provide greater comprehensibility and stylistic freedom that shading alone. A substantial challenge for making stylized line drawings from 3D models is the visibility computation. Current algorithms for computing line visibility in models of moderate complexity are either too slow for interactive rendering, or too brittle for coherent animation. We present a method that exploits graphics hardware to provide fast and robust line visibility. Rendering speed for our system is usually within a factor of two of an optimized rendering pipeline using conventional lines, and our system provides much higher visual quality and flexibility for stylization.

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The notion of quantitative invisibility and the machine rendering of solids

Cited by 131 publications

References 3 publications

Depth-Dependent Halos: Illustrative Rendering of Dense Line Data

Depth-Dependent Halos: Illustrative Rendering of Dense Line Data

Shadow algorithms for computer graphics

Fast high-quality line visibility

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