The effects of belongingness on the Simultaneous Lightness Contrast: A virtual reality study

Simultaneous Lightness Contrast (SLC) is the phenomenon whereby a grey patch on a dark background appears lighter than an equal patch on a light background. Interestingly, the lightness difference between these patches undergoes substantial augmentation when the two backgrounds are patterned, thereby forming the articulated-SLC display. There are two main interpretations of these phenomena: The midlevel interpretation maintains that the visual system groups the luminance within a set of contiguous frameworks, whilst the high-level one claims that the visual system splits the luminance into separate overlapping layers corresponding to separate physical contributions. This research aimed to test these two interpretations by systematically manipulating the viewing distance and the horizontal distance between the backgrounds of both the articulated and plain SLC displays. An immersive 3D Virtual Reality system was employed to reproduce identical alignment and distances, as well as isolating participants from interfering luminance. Results showed that reducing the viewing distance resulted in increased contrast in both the plain- and articulated-SLC displays and that, increasing the horizontal distance between the backgrounds resulted in decreased contrast in the articulated condition but increased contrast in the plain condition. These results suggest that a comprehensive lightness theory should combine the two interpretations

Perceptual Effects in Physically Based Animation with Rigid and Deformable Objects

We perform four psychophysical studies to investigate the perceptual effect of factors in the rendering and simulation stages of physically based animation production. Our study provides helpful insights in how to improve visual plausibility or reduce computational cost, which may allow artists to adjust their designs to enhance or minimize the perceived deformation in a model, or to choose a more efficient dynamics model and simpler mesh used in simulation without harming the visual plausibility. In our first study, we find that appearance can potentially influence people’s sensitivity to differences of deformation as well as subjective rating of softness. Further analysis shows that, in simple scenarios, the effect of low-level visual details in appearance can be dominant, even if high-level information delivered by appearance has the opposite implication. Another experiment shows that as the number of objects in a scenario increases, objects are perceived to be stiffer. In the second study, we quantitatively measure how different low-level visual details can influence people’s perceived stiffness of a deformable sphere under physically based simulation. We find that checkerboard pattern with certain combinations of spatial frequency and contrast can reduce the perceived stiffness. Our study further shows that adding a high-contrast checkerboard background can reduce such effect. In our third study, we discover that the resolution of a mesh used in the simulation of deformable objects can be reduced to a certain level without being noticed. For complex deformation, it is easier for people to recognize such reduction. Lastly, we verify two hypotheses which are assumed to be true only intuitively in many rigid body simulations in our third study. I: In large scale rigid body simulation, viewers may not be able to perceive distortion incurred by an approximated simulation method. II: Fixing objects under a pile of objects does not affect the visual plausibility. Our analysis of results supports the truthfulness of the hypotheses under certain simulation environments, but discovers four factors which may affect the authenticity of these hypotheses: number of collisions simulated simultaneously, homogeneity of colliding object pairs, distance from scene under simulation to camera position, and simulation method used

Visual Perception of Dynamic Properties and Events: Collisions and Throws

The central topic of this dissertation is visual perception of dynamic events. The topic is worth of interest, as witnessed by its long tradition in the history of Experimental Psychology, starting with the seminal work of Albert Michotte (1881 - 1965) on phenomenal causality. Thus, the topic I chose is not original in itself. However, a distinctive element of novelty in my dissertation is the use of Computer Graphics techniques as a means for creating realistic experimental stimuli in psychological experiments. Besides the advantage of reducing the gap between laboratory experiments and everyday experience, this may reveal the importance of experimental variables which traditionally have been ignored in research on visual perception of dynamic events. The reader should be informed that this dissertation is characterized by various lines of research, which are intrinsically connected with the central topic of visual perception of dynamic events. In some of the experiments, I investigate visual perception of dynamic events, whereas in others I investigate cognition of the same events. Two distinct dynamic events will be especially studied: horizontal collisions and throws. Moreover, the results of the experiments will be discussed not only in relation to their theoretical implications for psychological models, but also in relation to their potential applications to Physics education and Computer Graphics. As a result, the content of the dissertation is quite heterogeneous, but I hope to provide the reader with a broad and multidisciplinary perspective on the subject at hand. The dissertation is composed of five chapters, which may be divided into three groups. (i) In Chapters 1-3, after a presentation of the theoretical background of visual perception of dynamic events, I investigate the influence of dynamic properties of virtual objects on visual perception of horizontal collisions. The results of this research are important for the old and still active debate on phenomenal causality. (ii) In Chapter 4 I present a research on Naïve Physics of horizontal collisions between virtual spheres differing in simulated mass and velocity. In this chapter I take a more cognitive (rather than perceptual) perspective on dynamic events, investigating how people reason about the proposed physical event. (iii) In Chapter 5, I present a research on visual perception of virtual throwing animations, which are complex and rarely studied dynamic events. This chapter stands out for its multidisciplinary nature, as in it I discuss how the results can be applied to Computer Graphics. The research presented in this last chapter has been conducted as a part of my doctorate studies when I was a visiting PhD student at the Graphics, Vision, and Visualisation Group at Trinity College Dublin, where I collaborated with Professor Carol O’Sullivan and Doctor Ludovic Hoyet, who are computer scientists working on applications of visual perception to Computer Graphics. In more detail, in Chapter 1 I discuss the theoretical background of visual perception of dynamic events and phenomenal causality. Firstly, I focus on Michotte’s classical work. Secondly, I discuss some prominent issues which have been debated for a long time in this field of research. Lastly, I present White’s schema-matching model of visual perception of dynamic events, discussing its differences and similarities as compared with Michotte’s model. This chapter is intended to serve as a theoretical point of reference for the entire dissertation. In Chapter 2 I discuss the hypothesis that visually perceived dynamic properties of objects involved in dynamic events do influence visual perception of the dynamic events themselves. Firstly, I try to confute two popular arguments against this hypothesis. Then, I highlight the evolutionary advantage of visual perception of dynamic properties, discussing their possible influence on visual perception of dynamic events. Lastly, I discuss Runeson’s KSD model in relation to the presented hypothesis. In Chapter 3 I present three experiments which confirm the hypothesis discussed in Chapter 2. In particular, I show that simulated material (Experiment 1) and size (Experiments 2 and 3) of virtual objects involved in horizontal collisions strongly influence how observers perceive the event. I also discuss the theoretical implications of these findings by referring to Michotte’s and White’s models. In Chapter 4 I present a research on Naïve Physics of horizontal collisions. Firstly, I discuss the general importance of studying Naïve Physics for improving basic education in Physics. Secondly, I present Information Integration Theory and Functional Measurement methodology as suitable tools for the assessment of students’ intuitive knowledge of physical events, evidencing their advantages over multiple-choice surveys. Lastly, I present two experiments (conducted using Information Integration Theory and Functional Measurement) on Naïve Physics of horizontal collisions between simulated spheres differing in size, velocity, and material. The importance of the results for Physics instruction will also be discussed. Finally, in Chapter 5 I present a research on visual perception of edited virtual throwing animations. First I discuss the relations between visual perception of dynamic events (human motion in particular) and Computer Graphics. Then, I present two experiments on observers’ sensitivity to anomalies in realistic virtual throwing animations, discussing the importance of the results for videogames and movies industry

Simulation inkompressibler deformierbarer Körper

Die computergestützte Simulation von Bewegungsabläufen wird immer wichtiger in vielen Anwendungsgebieten. Einsatzgebiete von dynamischen Simulationen sind beispielsweise die Erstellung von Computeranimationen für Filme, Anwendungen in der virtuellen Realität oder für Computerspiele. In diesen Gebieten genügen oft plausible Ergebnisse, die dem Anwender das Gefühl einer realistischen Bewegung vermitteln. Hier kann die Simulation volumenerhaltender Körper zur Verbesserung der visuellen Plausibilität

Effect of scenario on perceptual sensitivity to errors in animation

A deeper understanding of what makes animation perceptually plausible would benefit a number of applications, such as approximate collision detection and goal-directed animation. In a series of psychophysical experiments, we examine how measurements of perceptual sensitivity in realistic physical simulations compare to similar measurements done in more abstract settings. We find that participant tolerance for certain types of errors is significantly higher in a realistic snooker scenario than in the abstract test settings previously used to examine those errors. By contrast, we find tolerance for errors displayed in realistic but more neutral environments was not different from tolerance for those errors in abstract settings. Additionally, we examine the interaction of auditory and visual cues in determining participant sensitivity to spatiotemporal errors in rigid body collisions. We find that participants are predominantly affected by visual cues. Finally, we find that tolerance for spatial gaps during collision events is constant for a wide range of viewing angles if the effect of foreshortening and occlusion caused by the viewing angle is taken into account