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Kevin Sanik, Manish Singh; The relative effectiveness of different line drawing algorithms at conveying 3D shape. Journal of Vision 2014;14(10):727. doi: https://doi.org/10.1167/14.10.727.
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© ARVO (1962-2015); The Authors (2016-present)
Line drawings depict 3D shape using "minimal" information. Computer graphics algorithms have used different geometric surface features to define lines. While no line definition is universally superior to others (Cole09), the conditions under which some line definitions outperform others, are not well understood. We examine the efficacy of two line definitions in conveying 3D shape. "Suggestive contours" are occlusions in nearby viewpoints (DeCarlo03). "Apparent ridges" are extrema of view-dependent curvature (Judd07). We expect that apparent ridges are more effective along sharper curvature extrema, while suggestive contours are more effective near more well-defined inflections. Thus, as a surface moves from a sharp sawtooth wave to a smooth sinusoidal wave, the better depiction should switch from apparent ridges to suggestive contours. Stimuli were lines drawings of surfaces with waves. They were generated by modulating the (a) radius of a cylinder, (b) height laterally on a plane or (c) height radially, using either (I) a sawtooth or (II) a sinusoidal wave. For the six resulting surfaces, one drawing using each line definition was created. We used the gauge figure methodology on Amazon's Mechanical Turk, and compared subjects' fitted settings to the ground truth of both the sawtooth and sine-wave versions. The results showed that, for sawtooth waves, apparent ridges were superior. For sinusoidal waves, the settings for the apparent ridge drawings more closely matched the sawtooth waves than the sine waves. They were thus perceived as sharper than the depicted surface. Performance of suggestive contours for sinusoidal waves varied depending on their interaction with other geometric features, such as occluding contours, parabolic lines, and ridges/valleys. The results suggest a new classification scheme for suggestive contours and apparent ridges that predicts when their usage is, or is not, effective. This can help line-drawing generation algorithms select effective lines to depict 3D shape.
Meeting abstract presented at VSS 2014
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