Changes in Perceived Object Shape with Changes in Lighting Model and Surface Properties

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 103-103 ◽  
Author(s):  
L T Maloney ◽  
P Mamassian ◽  
M S Landy
Keyword(s):  
Distribution Function ◽  
Surface Properties ◽  
Unbiased Estimate ◽  
Observer Performance ◽  
Surface Shape ◽  
Surface Reflectance ◽  
Object Shape ◽  
Black Background ◽  
Wooden Object ◽  
Real Objects

We examined the influence of lighting and bidirectional surface reflectance distribution function (BRDF) on the perceived shape of real objects viewed monocularly and binocularly. We asked observers to adjust a ‘circle-stick’ gradient probe optically superimposed on a smooth, asymmetric, pear-shaped wooden object placed directly in front of the observer at a distance of 60 cm. By using real objects, we avoid problems with unrealistic rendering algorithms and CRT presentation of stimuli. The lighting models used were simple (a single near-punctate source and a flat black background), the viewing conditions (in the binocular case) realistic, and the BDRFs selected not implausible. We did not assume that the viewer's perception of shape is veridical under any of the conditions considered, nor did we assume that surface shape estimated from gradient probe settings is an unbiased estimate of perceived shape. We sought to establish whether changes in lighting model and BRDF affect observer performance and, by implication, perceived shape. Observers viewed the object under all eight of the possible combinations of the binary factors: (a) monocular and binocular viewing of the object, (b) near-punctate illumination from above-left or above-right, and (c) matte wooden BRDF (the natural surface of the object) and gloss white BRDF (the same object painted). For each condition there was a total of ten gradient settings at each of over one hundred surface locations. The same locations were used for each of the eight conditions. We report results of analyses and discuss their implications.

scholarly journals One-shot BRDF imaging system to obtain surface properties

2021 ◽  
Author(s):  
Hiroshi Ohno ◽  
Takahiro Kamikawa
Keyword(s):  
Surface Properties ◽  
Imaging System ◽  
Reconstruction Method ◽  
Surface Reflectance ◽  
Bidirectional Reflectance Distribution Function ◽  
Bidirectional Reflectance ◽  
Color Mapping ◽  
System A ◽  
Cone Surface ◽  
Bidirectional Reflectance Distribution

AbstractThe bidirectional reflectance distribution function (BRDF) that describes an angle-resolved distribution of surface reflectance is available for characterizing surface properties of a material. A one-shot BRDF imaging system can capture an in-plane color mapping of light direction extracted from a surface BRDF distribution. A surface roughness identification method is then proposed here using the imaging system. A difference between surface properties of a matt paper and a glossy paper is experimentally shown to be detected using the method. A surface reconstruction method of an axisymmetric micro-object using the imaging system is also proposed here. The imaging system experimentally shows that it can reconstruct an axisymmetric aluminium cone surface with a height of 37 μm.

scholarly journals Joint Effects of Illumination Geometry and Object Shape in the Perception of Surface Reflectance

i-Perception ◽  
10.1068/i0480 ◽  
2011 ◽  
Vol 2 (9) ◽  
pp. 1014-1034 ◽  
Author(s):  
Maria Olkkonen ◽  
David H Brainard
Keyword(s):  
Surface Reflectance ◽  
Object Shape ◽  
Joint Effects

Methods of 3D Object Shape Acquisition

2013 ◽  
pp. 473-497
Author(s):  
Pavel Zemcik ◽  
Michal Spanel ◽  
Premysl Krsek ◽  
Miloslav Richter
Keyword(s):  
Surface Shape ◽  
Optical Methods ◽  
Object Shape ◽  
3D Object ◽  
Single View ◽  
Shape Acquisition ◽  
3D Data ◽  
3D Data Processing ◽  
Shape Processing ◽  
Surface Image

This chapter contains an overview of methods for a 3D object shape from both the surface and the internal structure of the objects. The acquisition methods of interest are optical methods based on objects surface image processing and CT/NMR sensors that explore the object volume structure. The chapter also describes some methods for 3D shape processing. The focus is on 3D surface shape acquisition methods based on multiple views, methods using single view video sequences, and methods that use a single view with a controlled light source. In addition, the volume methods represented by CT/NMR are covered as well. A set of algorithms suitable for the acquired 3D data processing and simplification are shown to demonstrate how the models data can be processed. Finally, the chapter discusses future directions and then draws conclusions.

scholarly journals Shape coding in occipito-temporal cortex relies on object silhouette, curvature, and medial axis

2020 ◽  
Vol 124 (6) ◽  
pp. 1560-1570
Author(s):  
Paolo Papale ◽  
Andrea Leo ◽  
Giacomo Handjaras ◽  
Luca Cecchetti ◽  
Pietro Pietrini ◽  
...  
Keyword(s):  
Medial Axis ◽  
Temporal Cortex ◽  
Shape Description ◽  
Multiple Features ◽  
Object Shape ◽  
Shape Models ◽  
Shape Coding ◽  
Brain Responses ◽  
Real Objects

There are several possible ways of characterizing the shape of an object. Which shape description better describes our brain responses while we passively perceive objects? Here, we employed three competing shape models to explain brain representations when viewing real objects. We found that object shape is encoded in a multidimensional fashion and thus defined by the interaction of multiple features.

scholarly journals High-resolution airborne imaging DOAS measurements of NO<sub>2</sub> above Bucharest during AROMAT

2017 ◽  
Vol 10 (5) ◽  
pp. 1831-1857 ◽  
Author(s):  
Andreas Carlos Meier ◽  
Anja Schönhardt ◽  
Tim Bösch ◽  
Andreas Richter ◽  
André Seyler ◽  
...  
Keyword(s):  
Surface Properties ◽  
Urban Areas ◽  
Strong Dependence ◽  
Horizontal Distribution ◽  
Optical Absorption Spectroscopy ◽  
Surface Reflectance ◽  
Emission Rates ◽  
Vertical Column ◽  
Airborne Imaging ◽  
The City

Abstract. In this study we report on airborne imaging DOAS measurements of NO2 from two flights performed in Bucharest during the AROMAT campaign (Airborne ROmanian Measurements of Aerosols and Trace gases) in September 2014. These measurements were performed with the Airborne imaging Differential Optical Absorption Spectroscopy (DOAS) instrument for Measurements of Atmospheric Pollution (AirMAP) and provide nearly gapless maps of column densities of NO2 below the aircraft with a high spatial resolution of better than 100 m. The air mass factors, which are needed to convert the measured differential slant column densities (dSCDs) to vertical column densities (VCDs), have a strong dependence on the surface reflectance, which has to be accounted for in the retrieval. This is especially important for measurements above urban areas, where the surface properties vary strongly. As the instrument is not radiometrically calibrated, we have developed a method to derive the surface reflectance from intensities measured by AirMAP. This method is based on radiative transfer calculation with SCIATRAN and a reference area for which the surface reflectance is known. While surface properties are clearly apparent in the NO2 dSCD results, this effect is successfully corrected for in the VCD results. Furthermore, we investigate the influence of aerosols on the retrieval for a variety of aerosol profiles that were measured in the context of the AROMAT campaigns. The results of two research flights are presented, which reveal distinct horizontal distribution patterns and strong spatial gradients of NO2 across the city. Pollution levels range from background values in the outskirts located upwind of the city to about 4  ×  1016 molec cm−2 in the polluted city center. Validation against two co-located mobile car-DOAS measurements yields good agreement between the datasets, with correlation coefficients of R =  0.94 and R =  0.85, respectively. Estimations on the NOx emission rate of Bucharest for the two flights yield emission rates of 15.1 ± 9.4 and 13.6 ± 8.4 mol s−1, respectively.

Methods of 3D Object Shape Acquisition

2012 ◽  
pp. 1-27
Author(s):  
Pavel Zemcik ◽  
Michal Spanel ◽  
Premysl Krsek ◽  
Miloslav Richter
Keyword(s):  
Surface Shape ◽  
Optical Methods ◽  
Object Shape ◽  
3D Object ◽  
Single View ◽  
Shape Acquisition ◽  
3D Data ◽  
3D Data Processing ◽  
Shape Processing ◽  
Surface Image

This chapter contains an overview of methods for a 3D object shape from both the surface and the internal structure of the objects. The acquisition methods of interest are optical methods based on objects surface image processing and CT/NMR sensors that explore the object volume structure. The chapter also describes some methods for 3D shape processing. The focus is on 3D surface shape acquisition methods based on multiple views, methods using single view video sequences, and methods that use a single view with a controlled light source. In addition, the volume methods represented by CT/NMR are covered as well. A set of algorithms suitable for the acquired 3D data processing and simplification are shown to demonstrate how the models data can be processed. Finally, the chapter discusses future directions and then draws conclusions.

Contrast Negation Impairs Sorting Unfamiliar Faces by Identity: A Comparison With Original (Contrast-Positive) and Stretched Images

Perception ◽  
2020 ◽  
pp. 030100662098220
Author(s):  
Adam Sandford ◽  
Dominica Pec ◽  
Angelisa N. Hatfield
Keyword(s):  
Image Quality ◽  
Surface Properties ◽  
Presentation Order ◽  
The Other ◽  
Informational Content ◽  
Surface Reflectance ◽  
Shape Information ◽  
Facial Identity ◽  
Unfamiliar Faces

Recognition of unfamiliar faces is difficult in part due to variations in expressions, angles, and image quality. Studies suggest shape and surface properties play varied roles in face learning, and identification of unfamiliar faces uses diagnostic pigmentation/surface reflectance relative to shape information. Here, participants sorted photo-cards of unfamiliar faces by identity, which were shown in their original, stretched, and contrast-negated forms, to examine the utility of diagnostic shape and surface properties in sorting unfamiliar faces by identity. In four experiments, we varied the presentation order of conditions ( contrast-negated first or original first with stretched second across experiments) and whether the same or different photo-cards were seen across conditions. Stretching the images did not impair performance in any measures relative to other conditions. Contrast negation generally exacerbated poor sorting by identity compared with the other conditions. However, seeing the contrast-negated photo-cards last mitigated some of the effects of contrast negation. Together, results suggest an important role for surface properties such as pigmentation and reflectance for sorting by identity and add to literatures on informational content and appearance variability in discrimination of facial identity.

scholarly journals High-resolution airborne imaging DOAS-measurements of NO<sub>2</sub> above Bucharest during AROMAT

2016 ◽  
Author(s):  
Andreas Carlos Meier ◽  
Anja Schönhardt ◽  
Tim Bösch ◽  
Andreas Richter ◽  
André Seyler ◽  
...  
Keyword(s):  
Surface Properties ◽  
Urban Areas ◽  
Strong Dependence ◽  
Horizontal Distribution ◽  
Optical Absorption Spectroscopy ◽  
Surface Reflectance ◽  
Emission Rates ◽  
Vertical Column ◽  
Airborne Imaging ◽  
The City

Abstract. In this study we report on airborne imaging DOAS measurements of NO2 from two flights performed in Bucharest during the AROMAT campaign (Airborne ROmanian Meeasurements of Aerosols an Trace gases) in September 2014. These measurements were performed with the Airborne imaging Differential Optical Absorption Spectroscopy (DOAS) instrument for Measurements of Atmospheric Pollution (AirMAP) and provide nearly gapless maps of column densities of NO2 below the aircraft with a high spatial resolution of better than 100 m. The airmass factors, which are needed to convert the measured differential Slant Column Densities (dSCDs) to Vertical Column Densities (VCDs) have a strong dependence on the surface reflectance, which has to be accounted for in the retrieval. This is especially important for measurements above urban areas, where the surface properties vary strongly. As the instrument is not radiometrically calibrated, we have developed a method to derive the surface reflectance from measured intensities at the aircraft. This method is based on radiative transfer calculation with SCIATRAN and a reference area for which the surface reflectance is known. While surface properties are clearly seen in the NO2 dSCD results, this effect is successfully corrected for in the VCD results. Furthermore we investigate the influence of aerosols on the retrieval for a variety of aerosol profiles that were measured in the context of the AROMAT campaigns. The results of two research flights are presented which reveal distinct horizontal distribution patterns and strong spatial gradients of NO2 across the city. Pollution levels range from background values in the outskirts located upwind of the city to about 4 × 1016 molec cm−2 in the polluted city center. Validation against two co-located mobile car-DOAS measurements yields good agreement between the datasets with correlation cofficients of R = 0.94 and R = 0.85, respectively. Estimations on the NOx emission rate of Bucharest for the two flights yield emission rates of 15.1 &amp;pm; 9.4 mol s−1 and 13.6 &amp;pm; 8.4 mol s−1, respectively.

scholarly journals Shape coding in occipito-temporal cortex relies on object silhouette, curvature and medial-axis

2019 ◽  
Author(s):  
Paolo Papale ◽  
Andrea Leo ◽  
Giacomo Handjaras ◽  
Luca Cecchetti ◽  
Pietro Pietrini ◽  
...  
Keyword(s):  
Medial Axis ◽  
Temporal Cortex ◽  
Brain Regions ◽  
Local Contrast ◽  
Object Representations ◽  
Shape Representations ◽  
Object Shape ◽  
Visual Hierarchy ◽  
Real Objects ◽  
Brain Processing

AbstractObject recognition relies on different transformations of the retinal input, carried out by the visual system, that range from local contrast to object shape and category. While some of those transformations are thought to occur at specific stages of the visual hierarchy, the features they represent are correlated (e.g., object shape and identity) and selectivity for the same feature overlaps in many brain regions. This may be explained either by collinearity across representations, or may instead reflect the coding of multiple dimensions by the same cortical population. Moreover, orthogonal and shared components may differently impact on distinctive stages of the visual hierarchy. We recorded functional MRI (fMRI) activity while participants passively attended to object images and employed a statistical approach that partitioned orthogonal and shared object representations to reveal their relative impact on brain processing. Orthogonal shape representations (silhouette, curvature and medial-axis) independently explained distinct and overlapping clusters of selectivity in occitotemporal (OTC) and parietal cortex. Moreover, we show that the relevance of shared representations linearly increases moving from posterior to anterior regions. These results indicate that the visual cortex encodes shared relations between different features in a topographic fashion and that object shape is encoded along different dimensions, each representing orthogonal features.New & NoteworthyThere are several possible ways of characterizing the shape of an object. Which shape description better describes our brain responses while we passively perceive objects? Here, we employed three competing shape models to explain brain representations when viewing real objects. We found that object shape is encoded in a multi-dimensional fashion and thus defined by the interaction of multiple features.

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