Observer strategies in perception of 3-D shape from isotropic textures: developable surfaces

AbstractWe document the limitations of isotropic textures in conveying three-dimensional shape. We measured the perceived shape and pitch of upright and pitched corrugated surfaces overlaid with different classes of isotropic textures: patterns containing isotropic texture elements, isotropically filtered noise patterns, and patterns containing ellipses or lines of all orientations. Frequency modulations arising from surface slant were incorrectly interpreted as changes in surface distance, resulting in concavities being misclassified as convexities, and right and left slants as concavities. In addition, images of pitched surfaces exhibited oriented flows that confound surface shape and surface pitch. Observers related oriented flow patterns to particular surface shapes with a bias for perceiving convex surfaces. When concave and convex curvatures were concurrently visible, the number of correct shape classifications increased slightly. Isotropic textures thus convey correct 3-D shapes of developable surfaces only in some conditions, and the same perceptual strategies lead to non-veridical percepts in other conditions

On the Optimization of Visualizations of Complex Phenomena

The problem of perceptually optimizing complex visualizations is a difficult one, involving perceptual as well as aesthetic issues. In our experience, controlled experiments are quite limited in their ability to uncover interrelationships among visualization parameters, and thus may not be the most useful way to develop rules-of-thumb or theory to guide the production of high-quality visualizations. In this paper, we propose a new experimental approach to optimizing visualization quality that integrates some of the strong points of controlled experiments with methods more suited to investigating complex highly-coupled phenomena. We use human-in-the-loop experiments to search through visualization parameter space, generating large databases of rated visualization solutions. This is followed by data mining to extract results such as exemplar visualizations, guidelines for producing visualizations, and hypotheses about strategies leading to strong visualizations. The approach can easily address both perceptual and aesthetic concerns, and can handle complex parameter interactions. We suggest a genetic algorithm as a valuable way of guiding the human-in-the-loop search through visualization parameter space. We describe our methods for using clustering, histogramming, principal component analysis, and neural networks for data mining. The experimental approach is illustrated with a study of the problem of optimal texturing for viewing layered surfaces so that both surfaces are maximally observable

View Direction, Surface Orientation and Texture Orientation for Perception of Surface Shape

Textures are commonly used to enhance the representation of shape in non-photorealistic rendering applications such as medical drawings. Textures that have elongated linear elements appear to be superior to random textures in that they can, by the way they conform to the surface, reveal the surface shape. We observe that shape following hache marks commonly used in cartography and copper-plate illustration are locally similar to the effect of the lines that can be generated by the intersection of a set of parallel planes with a surface. We use this as a basis for investigating the relationships between view direction, texture orientation and surface orientation in affording surface shape perception. We report two experiments using parallel plane textures. The results show that textures constructed from planes more nearly orthogonal to the line of sight tend to be better at revealing surface shape. Also, viewing surfaces from an oblique view is much better for revealing surface shape than viewing them from directly above

The influence of feature-based information in the age processing of unfamiliar faces

The influence of the internal features (eyes, nose, and mouth) in the age processing of unfamiliar faces was examined. Younger and older versions of the faces of six individuals (covering three different age ranges, from infancy to maturity) were used as donor stimuli. For each individual in turn, the effects on age estimates of placing older features in the younger face version (or vice versa) were investigated. Age estimates were heavily influenced by the age of the internal facial features. Experiment 2 replicated these effects with a larger number of faces within a narrower age range (after growth is complete and before major skin changes have occurred). Taken together, these two experiments show that the internal facial features may be influential in conveying age information to the perceiver. However, the mechanisms by which features exert their influence remain difficult to determine: although age estimates might be based on local information from the features themselves, an alternative possibility is that featural changes indirectly influence age estimates by altering the global three-dimensional shape of the head

Transition Contour Synthesis with Dynamic Patch Transitions

In this article, we present a novel approach for modulating the shape of transitions between terrain materials to produce detailed and varied contours where blend resolution is limited. Whereas texture splatting and blend mapping add detail to transitions at the texel level, our approach addresses the broader shape of the transition by introducing intermittency and irregularity. Our results have proven that enriched detail of the blend contour can be achieved with a performance competitive to existing approaches without additional texture, geometry resources, or asset preprocessing. We achieve this by compositing blend masks on-the-fly with the subdivision of texture space into differently sized patches to produce irregular contours from minimal artistic input. Our approach is of particular importance for applications where GPU resources or artistic input is limited or impractical

Pembinaan dan penilaian program rekabentuk rasuk keluli (PRRK) sebagai alat kognitif dalam pembelajaran rekabentuk struktur di kalangan pelajar diploma kejuruteraan awam KUiTTHO

Kajian awal yang telah dijalankan mendapati pelajar Kejuruteraan Awam KUiTTHO menghadapi masalah kognitif dalam pembelajaran mata pelajaran Rekabentuk Struktur khasnya dalam pemahaman konsep dan prosedur reka bentuk. Langkah pengiraan yang terlalu banyak selalunya mengelirukan pelajar sehinggakan mereka hilang minat dan tumpuan. Bagi membantu mereka, satu program telah disediakan dengan menggunakan perisian Microsoft Excel bagi tujuan menganalisis dan mereka bentuk rasuk keluli bagi meningkatkan tahap kemahiran kognitif terhadap matapelajaran tersebut. Program Rekabentuk Rasuk Keluli (PRRK) ini disediakan berdasarkan kaedah reka bentuk yang diamalkan oleh British Standard Institution, Structural Use of Steel Work In Building. Seramai dua puluh satu orang pelajar semester akhir Diploma Kejuruteraan A warn yang mengambil mata pelajaran Rekabentuk Struktur telah diminta menilai program ini. Penilaian telah dijalankan terhadap isi, sifat mesra pengguna dan kebolehlaksanaan program menggunakan kaedah skor min. Selain itu perkaitan antara pengalaman pelajar menggunakan komputer sebagai sumber pembelajaran dengan penilaian PRRK juga telah dilihat. Keputusan skor min menunjukkan isi PRKK adalah baik, bersifat mesra pengguna dan mempunyai sifat kebolehlaksanaan. Ujian korelasi Spearman pula menunjukkan bahawa tidak terdapat sebarang perkaitan yang signifikan di antara pengalaman pelajar menggunakan komputer sebagai sumber pembelajaran dengan penilaian PRRK

A Method for the Perceptual Optimization of Complex Visualizations

A common problem in visualization applications is the display of one surface overlying another. Unfortunately, it is extremely difficult to do this clearly and effectively. Stereoscopic viewing can help, but in order for us to be able to see both surfaces simultaneously, they must be textured, and the top surface must be made partially transparent. There is also abundant evidence that all textures are not equal in helping to reveal surface shape, but there are no general guidelines describing the best set of textures to be used in this way. What makes the problem difficult to perceptually optimize is that there are a great many variables involved. Both foreground and background textures must be specified in terms of their component colors, texture element shapes, distributions, and sizes. Also to be specified is the degree of transparency for the foreground texture components. Here we report on a novel approach to creating perceptually optimal solutions to complex visualization problems and we apply it to the overlapping surface problem as a test case. Our approach is a three-stage process. In the first stage we create a parameterized method for specifying a foreground and background pair of textures. In the second stage a genetic algorithm is applied to a population of texture pairs using subject judgments as a selection criterion. Over many trials effective texture pairs evolve. The third stage involves characterizing and generalizing the examples of effective textures. We detail this process and present some early results

The relative efficacy of cues for two-dimensional shape perception

AbstractThe visual system uses a variety of cues for form perception, including motion, color, binocular disparity, texture, and luminance. Physiological evidence suggests that these cues are processed by different neural mechanisms. Do the cues processed by some mechanisms convey any advantage for form perception when compared to cues processed by another? In response to this question we assessed the relative efficiency of several cues in conveying two-dimensional form from background noise. For the sake of comparison, every cue type used the same experimental design and stimulus set. Our results confirm that movement is one of the most efficient cues for shape perception. Also, a simple transient cue (an instantaneous flashing on or off) is equally useful. In comparison, local dot density (a type of texture cue) was the least efficient. The efficiencies of most other cues, such as color, stereopsis, and relative movement in noise, were conspicuously similar