ISBCS 2020 – Effect of expectations on perception of dynamic material properties

Authors – Amna Malik, Katja Doerschner, Hüseyin Boyaci

The current global situation that we are all facing has forced us to look to the virtual world in order to continue within academia and research. Amna Malik, hosted by the University of Bilkent, has done just, virtually narrating her video for ISBCS presentation.

In the abstract Amna says:

“Visual information plays a vital role in object and material recognition. Based on our daily life interaction with objects, our brain learns to make associations between how an object looks like, what material it is made of and its physical and functional properties. Hence, before even we touch an object, simply by looking at it, we have expectations about how it will behave under different forces. For example, we expect a wine glass to shatter if it falls and hits the ground. Upon viewing an object, incoming visual information is combined with prior knowledge to help us recognizing objects, accessing their properties and making efficient decisions regarding actions involving interaction with objects. In this study we aimed to investigate the role of expectations in perception of material properties in dynamic scenes and how they affect perceptual decisions. We used novel computer animations of objects falling on ground, which are manipulated to behave in an expected or unexpected manner. Observers were asked to answer whether the object broke or not upon hitting the ground. We measured reaction times and percent correct responses for each condition. We found out that observers take longer to respond in the surprising condition. Hence, we concluded that expectations influence perception of dynamic material properties and perceptual decision making is delayed when these expectations are violated, which implies that additional processing is required when incoming sensory information does not match the expectations.”

We would like to congratulate Amna on a terrific presentation and encourage everyone to watch the video!

Self-isolation tips

From Ellen De Korte

Our researchers, supervisors and partners across Europe are all finding their way through this new reality. Ellen De Korte, based at the University of Bradford, has shared some insight into how she plans to work and live during the lockdown period in the UK.

I start my day with a 15-minute power yoga workout. While we are still able to go outside for an hour, I plan to walk to the nearest park if I can over lunchtimes. In order to maintain a bit of structure and combat loneliness, I make a schedule of whom I speaking to (either on the phone or video-conferencing) on a nice Yorkshire themed calendar

Ellen has also shared a picture of her “home office” set-up.

Ellen De Korte home office set-up

Visual Science of Art Conference 2019

Written by Jacob Cheeseman

As someone who considers himself a scientist first, and an artist second, I came to the Visual Science of Art Conference (VSAC) 2019 with keen interest. The meeting aims to enhance our scientific understanding of how visual artists depict the world, and to further communication between fields that, while traditionally divided within academia, share a passion for seeing.
This year we were gathered in Leuven, Belgium, a city that could well have the perfect balance of culture and functionality. And the opening reception was held at the Stadhuis, an absolutely gorgeous example of 15th-century gothic architecture. Our group was welcomed in this grand hall by no less than the mayor of Leuven, Mohamed Ridouani, whose presence signified how this alliance of art and science has strengthened both communities.

Stadhuis van Leuven

The content of the meeting spanned a range of diverse topics, including the visual perception of material properties, empirical aesthetics, and historical studies of rendering techniques. There was also no shortage of visual art—the work of Maaike Schoorel being a notable example. Working from reference photographs of real scenes, she paints a kind of phantasmic representation of the original image, accentuating only the critical lines and shading that suggest the underlying forms. The effect is to break any photographic constraints on interpretation, and to allow each viewer to project their own imagery onto the canvas.

Maaike Schoorel, Oranje Boterbloemen (Orange Buttercups), oil on canvas, 2011

The work I presented at the conference also deals with visual ambiguity, specifically the kind that depends on how we estimate distances in photographs. In everyday circumstances, our ability to identify surface material properties is effortless and automatic, but occasionally this ability can be challenged, especially when the visual pattern impedes a reliable estimation of distance. This can be seen in aerial photographs of planted fields, which can appear strikingly similar to woven fabric or textile. The pattern of light does not specify which interpretation is correct, and so our interpretations reveal what distances we have learned to associate with such images.

Jacob R. Cheeseman, Hunting for Ambiguity, photograph, 2018

In Jan Koenderink’s latest book, The Way of The Eye, he frames visual perception as a process of continually questioning our interpretations of images. Our first impression of what we are looking at is usually quite convincing, but if we relax our focus, other impressions enter into view. Surrealist painters like Dali seem to possess a supernatural talent for imagining multiple interpretations simultaneously, but how to compose photographs with this property strikes me as a slightly different, and perhaps more difficult task. When I asked Dr. Koenderink how one could compose such images, he suggested that it was a matter of attentional training.

To this end, I once spent a sunny afternoon in Giessen wandering around with my camera, hunting for ambiguous scenes. Although my perception of each scene was stable, by meditating on the question, “What else could this be?”, I began to see hints of possibility. By the end of that day I had hundreds of images, but not a clue whether any of them had captured what I had seen, or whether others would agree with my interpretations. One of my basic goals at VSAC was therefore to discuss this way of seeing with visual artists who play with ambiguity.

My line of questioning went something like this: “How does one compose images with multiple interpretations? While creating visual art, are you trying to reduce disparity between a mental image and a perceived image? Does one interpretation serve as the foundation for subsequent layers?” The answers I received to these questions were also rather ambiguous, which could mean that these are not the right questions, or that I am not ready for the answers. Maybe by the time this discussion resumes at next year’s meeting, I will be.

A Study in Gloss

Secondment review by Sina Mehraeen

One’s ideas must be as broad as Nature if they are to interpret Nature
                                                                                     ― Arthur Conan Doyle

Here are the chronicles of my adventures during my secondment at the Department of Psychology, University of Southampton, under the supervision of Prof. Wendy Adams and Prof. Marc Ernst.

The Objectives of the trip:

  1. Gain an understanding of the interaction between illumination and material perception, including analysis of spherical high dynamic range natural illumination environments.
  2. Gain experience of working in a Psychology department in another EU country.

To begin at the beginning, I was excited to work with Wendy and to be exposed to the cool research she does on material perception, illumination environments and rendering virtual objects.  I had also never been to the UK, and was eager to get a glimpse of that part of the world.

The plan was twofold; first, I would conduct a pilot study on the interaction between illumination and gloss and how gloss might affect the way we manipulate a physical object. At the same time, I would try to learn as much as possible on rendering virtual objects in natural illumination environments and learn the statistics involved.

Sample HDR illumination environment sourced from the Southampton-York Natural Scenes (SYNS) Dataset. The SYNS dataset is a collection of high definition images (and their relevant metadata) from around 100 rural and urban locations.

After a short trip to a metal supermarket, we got some nice aluminum box pipes which we would use as our physical stimuli. The main question we were seeking to address with these physical objects is whether their glossiness affects the way people handle them. This is in line with previous studies looking at the relationship between gloss and touch (Kerrigan, Adams, & Graf, 2010 ; Adams, Kerrigan & Graf, 2016).

Aluminum box pipe

Once the objects were cleaned and nicely polished, we started testing out a suitable experimental setup. This proved more challenging than expected due to the unpredictable nature of natural lighting. In order to get the desired outcome, we really had to control the angle and intensity of illumination so using natural lighting was out of the question. We also tested various coatings to get the objects to be as glossy as possible. Currently, we have made some tweaks to the set up and we are in the process of data collection; so more info coming soon.

On the side and as a secondary objective, I began learning the basics of Blender to generate virtual objects and to import them as .obj files into Octane Render. Octane is fast rendering engine which allows for easy manipulation of minute elements which make up a scene, e.g. material qualities an object might possess and how those certain qualities (e.g. surface reflectance) interact with light. Once we had set those parameters, we placed them in a natural illumination environment and got something that looked like this:

A virtual object placed in a natural illumination environment

To conclude, I’d like to thank Wendy, Marc and Erich for their continuous support during my stay and also Davide and Paul for helping me with the setup. I’d also like to say a big thanks to everyone I had the good fortune of meeting at the Department of Psychology in Soton; for showing me around town and volunteering to participate in the experiment. Looking forward to seeing you all again soon.


ECVP 2019 ESR Abstracts

ECVP 2019 ESR Abstracts

The ECVP have now released the full abstracts of the attendees to the conference in Leuven. Below you will find the abstracts submitted by DyViTo ESRs. To see the full abstract book, including the abstracts that involve DyViTo Supervisors and friends of the project, please use this link.

Scale ambiguities in material recognition
Jacob R. Cheeseman*, Filipp Schmidt, Roland W. Fleming
Justus Liebig University Giessen

As a rule, observers can reliably identify the material properties of surfaces. Here, we investigated exceptions to this rule using a set of 87 photographs of materials (e.g., water, sand, stone, metal, wood) that appear to belong to different material classes depending on their apparent distance from the viewer. In three experiments, participants viewed each image and provided a categorical judgement of the depicted material, and a quantitative estimate of the distance between the camera and surface. Experiment 1 manipulated interpretations of these images by instructing two groups of participants to imagine a small or large distance between the camera and surface, while a third control group received no such instruction. In Experiments 2 and 3 interpretations were manipulated by providing visual cues for scale (e.g., objects of familiar size), which were presented alongside the target image or digitally inserted into the image. Results indicate that these manipulations can cause identical images to appear to belong to different material classes (e.g., water vs. marble), and that susceptibility to context information (i.e., material ambiguity) correlates with higher variability in distance estimates. Under challenging conditions, therefore, the recognition of some materials is vulnerable to simple manipulations of apparent scale.

Colour Variations within Light Fields: Interreflections and Colour Effects
Cehao Yu* (1), Elmar Eisemann (2), Sylvia Pont (1)
1: Perceptual Intelligence lab, TUDelft; 2: Computer Graphics and Visualization Group, TUDelft

The human visual system incorporates knowledge about local chromatic and lightness effects of interreflections (Bloj et al., Nature, 1999). Here we study basic principles behind chromatic effects of interreflections using computational modelling and photometric measurements. The colour of interreflections varies as a function of the number of bounces they went through. Using a computational model we found that those colour variations can show brightness, saturation and even hue shifts. Using a chromatic Mach Card, a concave folded card with both sides made of the same colour, we demonstrated those three types of colour effects empirically. Finally, we tested the effects of such coloured interreflections on light fields in 3D spaces. Via cubic spectral illuminance measurements in both computer simulations and full mock up room settings under different furnishing scenarios we measure the chromatic variations of first order properties of light fields. The types of chromatic variations were found to depend systematically on furnishing colour, lighting and geometry, as predicted, and also vary systematically within the light field, and thus throughout the space. We will next compare the physical light fields with visual light fields (including chromatic properties) and test perceived material colours, for (combinations of) the three types of effects.

Visual and haptic softness dimensions
Müge Cavdan* (1), Knut Drewing (1), Katja Doerschner (1,2,3)
1: Justus Liebig University Giessen, Germany; 2: Department of Psychology, Bilkent University, Ankara, Turkey; 3: National Magnetic Resonance Research Center, Bilkent University, Ankara, Turkey

When investigating visually or haptically perceived softness of materials researchers have typically equated softness with compliance. However, softness entails more aspects than this single dimension: a rabbit’s fur is soft in a different way than sand on Siesta beach and both’s softness is not necessarily related to the materials’ compliance. Here we investigated the dimensionality of perceived softness in visual and haptic domains. We asked participants to rate various materials on different adjectives. In the haptic experiment, participants were blindfolded and rated materials after haptically exploring them, whereas in the visual experiment they made the same ratings while looking at close up images of the same materials used in the haptic experiment. Principal component analyses revealed that both haptic and visual perception of softness are similarly organized in perceptual space, both containing dimensions of granularity, visco-elasticity, and deformability. However, furriness existed only in the haptic experiment. Moreover, the explained variance was higher in the haptic experiment, which suggests that the perceived dimensions of softness might be more accessible through haptic exploration than by looking at images of materials. Overall, these results contribute to our understanding of how visual and haptic information about material properties are processed and integrated.

Recognising materials over time
Ellen E M De Korte* (1), Andrew J Logan (2), Marina Bloj (1)
1: School of Optometry and Vision Science, University of Bradford, United Kingdom; 2:Department of Vision Sciences, Glasgow Caledonian University, United Kingdom

Materials change over time; colours fade and surfaces are scratched. These changes alter the retinal input and yet we still recognise them as the same material. When textiles are washed and laid out to dry we still identify them as the same fabric even though their colour visibly changes. The present study evaluated the appropriateness of an existing calibrated photograph set as a stimulus for studying the perception of appearance changes of materials over time. Participants (N = 4) reported which of the 2 pairs of images shown displayed the largest perceptual difference. Images were blocked (210 trials per block and participant) by material (Banana, Copper, Granite, Quilted Paper). Individual observers’ perceptual scales, estimated with Maximum Likelihood Difference Scaling via the General Linear Model estimation method, for each material were similar and showed that some, but not all, photographs were perceptually distinct. Thus, the calibrated photographs seem suitable for our purposes. Next steps will include image-based manipulations to establish which parameters drive the development of perceptual scales. Specifically, this will involve converting images to grayscale and manipulate image marks, such as brown staining in Banana images, in order to test the effects of colour and characteristic marks, respectively.