A J van Doorn

Delft University of Technology, Delft, South Holland, Netherlands

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Publications (126)136.69 Total impact

  • Jan Koenderink · Andrea Van Doorn · Vebjørn Ekroll
    No preview · Article · Apr 2016 · ACM Transactions on Applied Perception
  • Baingio Pinna · Andrea van Doorn · Johan Wagemans · Jan Koenderink
    [Show abstract] [Hide abstract] ABSTRACT: Many pictures are approximately piecewise uniform quilts. The patches meet in transitional areas that have a vague, ribbon-like geometry. These borders may occasionally get lost and sometimes pick up again, creating a ‘passage’ that partly blends adjacent patches. This type of structure is widely discussed in treatises on painting technique. Similar effects (lost outlines, passages) occur in drawing. The border regions are characterized by width, or sharpness and amplitude – which is the contrast between the patches on each side. Moreover, border regions have various textural structures. We propose a formal theory of such transitions. Images can be understood as superpositions of border areas. Stylistic changes can be implemented through the selective treatment of borders. The theory is formally similar to, though crucially different in meaning from, the theory of ‘edges’ (a technical term) in image processing. We propose it as a formal framework that enables principled discussion of ‘edge qualities’ (a term used by painters in a way unrelated to the use of ‘edge’ in image processing) in a well-structured manner.
    No preview · Article · Feb 2016
  • Jan Koenderink · Andrea van Doorn · Robert Pepperell · Baingio Pinna
    [Show abstract] [Hide abstract] ABSTRACT: Are pictorial renderings that deviate from linear perspective necessarily ‘wrong’? Are those in perfect linear perspective necessarily ‘right’? Are wrong depictions in some sense ‘impossible’? Linear perspective is the art of the peep show, making sense only from one fixed position, whereas typical art works are constructed and used more like panel presentations, that leave the vantage point free. In the latter case the viewpoint is free; moreover, a change of viewpoint has only a minor effect on pictorial experience. This phenomenologically important difference can be made explicit and formal, by considering the effects of panning eye movements when perusing scenes, and of changes of viewpoint induced by translations with respect to pictorial surfaces. We present examples from formal geometry, photography, and the visual arts.
    No preview · Article · Feb 2016 · Asia Pacific Journal on Human Rights and the Law
  • Baingio Pinna · Jan Koenderink · Andrea van Doorn
    [Show abstract] [Hide abstract] ABSTRACT: Here, we address the phenomenology of visual objects, using verbal reports, spontaneous descriptions, answers to questions and responses to suggestions, as well as free associations. We occasionally ask for simple sketches. Such methods allow probing of the deep structure of visual awareness. This is above all revealed by what is not spontaneously mentioned, or is only mentioned by way of incidental properties. It is also disclosed by changes induced by minor variations or additions. We find remarkable agreement over a large number of participants. Thus verbal reports are a powerful probe of visual structure. Similarly to language, "simple visual objects" have deep roots in subsidiary awareness. These "invisible" foundations serve to define simple figures, like a "square", as unique, prototypical objects. The nature of "visual objects" thus involves an extensive "invisible" realm. Without taking this into account, a proper understanding of the nature of the visual object is not possible. Finally, this should lead to a formal syntactical theory of basic visual shapes.
    No preview · Article · Oct 2015 · Philosophia Scientiae
  • Jan Koenderink · Andrea van Doorn · Johan Wagemans
    [Show abstract] [Hide abstract] ABSTRACT: Three observers performed a task designed to quantify their “pictorial relief” in visual awareness for a photograph of a piece of sculpture. In separate sessions, they were instructed to assume one of two “mental viewpoints.” The main objective was to investigate whether human observers have such command. All three observers could redirect their “mental view direction” by up to 20°. These observers experience “paradoxical monocular” stereopsis, whereas a sizable fraction of the population does not. Moreover, they had some experience in assuming various “viewing modes.” Whereas one cannot generalize to the population at large, these findings at least prove that it is possible to direct the mental viewpoint actively. This is of importance to the visual arts. For instance, academic drawings require one to be simultaneously aware of a “viewing” (for the drawing) and an “illumination direction” (for the shading). Being able to mentally deploy various vantage points is a crucial step from the “visual field” to the “visual space.”
    No preview · Article · Oct 2015 · i-Perception
  • Robert Pepperell · Jan Koenderink · Andrea van Doorn · Baingio Pinna
    [Show abstract] [Hide abstract] ABSTRACT: Do generic observers in their free-style viewing of postcard-size pictures have a preference for specific modes of perspective rendering? This most likely depends upon the phrasing of the question. Here we consider the feeling of ‘presence’: does the observer experience a sense of being ‘immersed in the scene’? We had 40 Italian naïve participants and 19 British art students rate three types of rendering of ten ‘typical holiday pictures’. All pictures represented 130° over the width of the picture. They were rendered in linear perspective, Hauck maps, and Postel maps. The results are clearcut. About a quarter of the participants prefer linear perspective, whereas the Hauck map is preferred by more than half of the participants. Naïve observers and art students agree. Architectural scenes are somewhat more likely to be preferred in perspective. Preferences are not randomly distributed, but participants have remarkable idiosyncratic affinities, a small group for perspective projection, a larger group for the Hauck map. Such facts might find application in the viewing of photographs on handheld electronic display devices.
    No preview · Article · Oct 2015 · Asia Pacific Journal on Human Rights and the Law
  • Jan Koenderink · Andrea van Doorn · Johan Wagemans
    [Show abstract] [Hide abstract] ABSTRACT: Local solid shape applies to the surface curvature of small surface patches—essentially regions of approximately constant curvatures—of volumetric objects that are smooth volumetric regions in Euclidean 3-space. This should be distinguished from local shape in pictorial space. The difference is categorical. Although local solid shape has naturally been explored in haptics, results in vision are not forthcoming. We describe a simple experiment in which observers judge shape quality and magnitude of cinematographic presentations. Without prior training, observers readily use continuous shape index and Casorati curvature scales with reasonable resolution.
    No preview · Article · Oct 2015 · i-Perception
  • Liliana Albertazzi · Jan J Koenderink · Andrea van Doorn
    [Show abstract] [Hide abstract] ABSTRACT: In our study, for a small number of antonyms, we investigate whether they are cross-modally or ideaesthetically related to the space of colors. We analyze the affinities of seven antonyms (cold-hot, dull-radiant, dead-vivid, soft-hard, transparent-chalky, dry-wet, and acid-treacly) and their intermediate connotations (cool-warm, matt-shiny, numb-lively, mellow-firm, semi-transparent-opaque, semi-dry-moist, and sour-sweet) as a function of color. We find that some antonyms relate to chromatic dimensions, others to achromatic ones. The cold-hot antonym proves to be the most salient dimension. The dry-wet dimension coincides with the cold-hot dimension, with dry corresponding to hot and wet to cold. The acid-treacly dimension proves to be transversal to the cold-hot dimension; hence, the pairs mutually span the chromatic domain. The cold-hot and acid-treacly antonyms perhaps recall Hering's opponent color system. The dull-radiant, transparent-chalky, and dead-vivid pairs depend little upon chromaticity. Of all seven antonyms, only the soft-hard one turns out to be independent of the chromatic structure.
    No preview · Article · Aug 2015 · Perception
  • Jan Koenderink · Andrea Van Doorn
    No preview · Article · Aug 2015 · Perception
  • [Show abstract] [Hide abstract] ABSTRACT: We consider techniques used in the articulation of pictorial relief. The related ‘cue’ best known to vision science is ‘shading’. It is discussed in terms of an inverse optics algorithm known as ‘shape from shading’. However, the familiar techniques of the visual arts count many alternative cues for the articulation of pictorial relief. From an art technical perspective these cues are well known. Although serving a similar purpose as shading proper, they allow a much flatter value scale, making it easier to retain the picture plane, or major tonal areas. Vision research has generally ignored such methods, possibly because they lack an obvious basis in ecological optics. We attempt to rate the power of various techniques on a common ‘shading scale’. We find that naive observers spontaneously use a variety of cues, and that several of these easily equal, or beat, conventional shading. This is of some conceptual interest to vision science, because shading has a generally acknowledged ecological basis, whereas the alternative methods lack this.
    No preview · Article · Mar 2015
  • Jan Koenderink · Andrea van Doorn · Johan Wagemans
    [Show abstract] [Hide abstract] ABSTRACT: The visual field is the spatial form of visual awareness, that is, immediate visual experience ignoring qualities and meanings. Such an entity only exists in the discursive representation, for the awareness as such is quality and meaning throughout. Thus the discursive, formal treatment is necessarily limited. We identify a number of important distinctions of a geometrical nature. This description is confronted with experimental phenomenology, that is the psychology of the Gestalt Schools, and with well known principles of artistic practice. We also trace the connections with biology, especially ethology, aesthetics, and the field of cognitive science based upon Cassirer’s concept of symbolic forms.
    No preview · Article · Feb 2015 · Pattern Recognition Letters
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    [Show abstract] [Hide abstract] ABSTRACT: The Poggendorff illusion is one of the most exhaustively studied illusions. Can it be revived as an interesting problem? Perhaps by moving it to a slightly different domain. Here, we consider the occlusion of a subjectively linear ramp of tonal values. In a simple experiment, we find results closely resembling those of the geometrical Poggendorff. Yet, the "explanations" offered for the latter hardly apply to the former case. Depending upon one's perspective, this may be taken to "revive" the Poggendorff illusion.
    Full-text · Article · Jan 2015 · Perception
  • [Show abstract] [Hide abstract] ABSTRACT: Does human vision deploy a generic template for open landscapes that might fit the gist of current optical input? In an experiment, participants judged depth order in split-field images in which the two fuzzily delineated half-images were filled with different hues. For the majority of observers, we find a systematic dependence of depth order of these half-images on their hue and/or brightness difference. After minor cleaning of the data, we are left with two mutually wellseparated clusters. Correlation with the statistical distribution of hue and brightness in generic "open landscape" photographs reveals that one cluster correlates with hue, the other with brightness. This suggests that human observers indeed at least partly rely on "generic landscape" templates in the psychogenesis of their visual awareness.
    No preview · Article · Jan 2015 · i-Perception
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    Jan Koenderink · Andrea van Doorn · Johan Wagemans
    [Show abstract] [Hide abstract] ABSTRACT: How is pictorial relief represented in visual awareness? Certainly not as a "depth map," but perhaps as a map of local surface attitudes (Koenderink & van Doorn, 1995). Here we consider the possibility that observers might instead, or concurrently, represent local surface shape, a geometrical invariant with respect to motions. Observers judge local surface shape, in a picture of a piece of sculpture, on a five-point categorical scale. Categories are cap-ridge-saddle-rut-cup-flat, where "flat" denotes the absence of shape. We find that observers readily perform such a task, with full resolution of a shape index scale (cap-ridge-saddle-rut-cup), and with excellent self-consistency over days. There exist remarkable inter-observer differences. Over a group of 10 naive observers we find that the dispersion of judgments peaks at the saddle category. There may be a relation of this finding to the history of the topic-Alberti's (1827) omission of the saddle category in his purportedly exhaustive catalog of local surface shapes.
    Preview · Article · Aug 2014 · Perception
  • Jan Koenderink · Andrea van Doorn
    [Show abstract] [Hide abstract] ABSTRACT: Shading is one of the generic “monocular depth (and shape) cues”. It is of conceptual interest because it apparently implies “causal relations” between the geometry of the scene in front of the observer, the formal description of brain activity, and the visual awareness of the observer. These are three disjunct ontological levels, so the very notion of “causal connections” is problematic. Some silent assumptions in current accounts indeed invoke “magic”, we identify internal and external local sign as instances.We attempt an account of the shading cue that avoids at least some of these pitfalls. We conclude that (for the human observer, machine vision has different objectives) the shading cue allows “direct perception” of surface shape.
    No preview · Chapter · Jan 2014
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    Andrea van Doorn · Jan Koenderink · Johan Wagemans
    [Show abstract] [Hide abstract] ABSTRACT: "Exocentric pointing in the visual field" involves the setting of a pointer so as to visually point to a target, where both pointer and target are objects in the visual field. Phenomenologically, such pointings show systematic deviations from veridicality of several degrees. The errors are very small in the vertical and horizontal directions, but appreciable in oblique directions. The magnitude of the error is largely independent of the distance between pointer and target for stretches in the range 2-27°. A general conclusion is that the visual field cannot be described in terms of one of the classical homogeneous spaces, or, alternatively, that the results from pointing involve mechanisms that come after geometry proper has been established.
    Preview · Article · Dec 2013 · Perception
  • J. J. Koenderink · A. J. van Doorn · S. C. Pont
    [Show abstract] [Hide abstract] ABSTRACT: When a light source moves, the isophotes of the illuminance field (observed as “shading” in the case of Lambertian surfaces) move over the surfaces of illuminated objects. The sense of rotation of the isophotes relative to the sense of rotation of the “surface illuminance flow,” that is the tangential component of the illumination direction over the surface, depends on the Gaussian curvature of the surface. The temporal change of orientation, the “shading twist,” reveals this purely surface related quality. Since the shading twist depends only on the local curvature of the surface it doesn’t matter at all how the light source moves or where the light sources are, the “shading twist” is a pure surface property, that is to say, it behaves as being painted upon the surface. The formal relations pertaining to the shading twist are analyzed and a numerical simulation is presented that fully corroborates the conclusions from the formal study. The algorithm is also tested on a real scene.
    No preview · Article · Oct 2013 · International Journal of Computer Vision
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    Jan Koenderink · Andrea van Doorn · Johan Wagemans
    [Show abstract] [Hide abstract] ABSTRACT: SFS (Shape From Shading) theory is based upon the Lambertian paradigm. Our visual demonstrations imply that this paradigm fails to apply to the conventional stimuli used to probe vision.
    Preview · Article · May 2013 · i-Perception
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    Jan Koenderink · Maarten Wijntjes · Andrea van Doorn
    [Show abstract] [Hide abstract] ABSTRACT: The "zograscope" is a "visual aid" (commonly known as "optical machine" in the 18th century) invented in the mid-18th century, and in general use until the early 20th century. It was intended to view single pictures (thus not stereographic pairs) with both eyes. The optics approximately eliminates the physiological cues (binocular disparity, vergence, accommodation, movement parallax, and image blur) that might indicate the flatness of the picture surface. The spatial structure of pictorial space is due to the remaining pictorial cues. As a consequence, many (or perhaps most) observers are aware of a heightened "plasticity" of the pictorial content for zograscopic as compared with natural viewing. We discuss the optics of the zograscope in some detail. Such an analysis is not available in the literature, whereas common "explanations" of the apparatus are evidently nonsensical. We constructed a zograscope, using modern parts, and present psychophysical data on its performance.
    Full-text · Article · May 2013 · i-Perception
  • Jan Koenderink · Andrea van Doorn
    [Show abstract] [Hide abstract] ABSTRACT: In The Problem of Form (1893), the German sculptor Adolf Hildebrand distinguishes categorically between perception obtained from multiple fixations or vantage points (G.: Bewegungsvorstellungen; we call these ‘assemblages’), and from purely ‘iconic’ imagery (G.: Fernbilder). Only the latter he considers properly ‘artistic’. Hildebrand finds the reason for this ontological distinction in the microgenesis of visual awareness. What to make of this? We analyze the various ‘modes of seeing’ in some detail. The conceptual issues involved are fundamental, and relevant to both vision science and the visual arts.
    No preview · Article · Jan 2013

Publication Stats

6k Citations
136.69 Total Impact Points

Institutions

  • 2009-2011
    • Delft University of Technology
      • Department of Industrial Design
      Delft, South Holland, Netherlands
  • 1972-2010
    • Universiteit Utrecht
      • • Department of Physics and Astronomy
      • • Division of Physics of Man
      • • Division of Zoological Medicine
      • • Laboratory for Physical Geography
      Utrecht, Utrecht, Netherlands
  • 2001
    • Cambridge College
      Cambridge, Massachusetts, United States
  • 1992-1994
    • Netherlands Institute for Space Research, Utrecht
      Utrecht, Utrecht, Netherlands
  • 1974
    • University of Groningen
      • Department of Psychology
      Groningen, Groningen, Netherlands