Author |
Description
|
Download |
P. M. Orzechowski | Pinching sweaters on your phone – iShoogle : multi-gesture touchscreen fabric simulator using natural on-fabric gestures to communicate textile qualities Ph.D. thesis, School of Mathematical and Computer Sciences, Heriot-Watt University, 2016. Abstract |
|
D. A. Robb | Crowdsourced Intuitive Visual Design Feedback Ph.D. thesis, School of Mathematical and Computer Sciences, Heriot-Watt University, 2015. Abstract It is concluded that the visual feedback method would be more appealing than text for that section of the population who may be of a visual cognitive style. Indeed the evaluation studies are evidence that such users believe images are as good as text when communicating their emotional reaction about a design. Designer participants reported being inspired by the visual feedback where, comparably, they were not inspired by text. They also reported that the feedback can represent the perceived mood in their designs, and that they would be enthusiastic users of a service offering this new form of visual design feedback. |
|
X. Dong | Perceptual Texture Similarity Estimation Ph.D. thesis, School of Mathematical and Computer Sciences, Heriot-Watt University, 2014. Abstract In the first part of this thesis, we conducted two evaluation experiments on the ability of 51 computational feature sets to estimate perceptual texture similarity using two different evaluation methods, namely, pair-of-pairs based and retrieval based evaluations. These experiments compared the computational features to two sets of human derived ground-truth data, both of which are higher resolution than those commonly used. The first was obtained by free-grouping and the second by pair-of-pairs experiments. Using these higher resolution data, we found that the feature sets do not perform well when compared to human judgements. Our analysis shows that these computational feature sets either (1) only exploit power spectrum information or (2) only compute higher order statistics (HoS) on, at most, small local neighbourhoods. In other words, they cannot capture aperiodic, long-range spatial relationships. As we hypothesise that these long-range interactions are important for the human perception of texture similarity we carried out two more pair-of-pairs experiments, the results of which indicate that long-range interactions do provide humans with important cues for the perception of texture similarity. In the second part of this thesis we develop new texture features that can encode such data. We first examine the importance of three different types of visual information for human perception of texture. Our results show that contours are the most critical type of information for human discrimination of textures. Finally, we report the development of a new set of contour-based features which performed well on the free-grouping data and outperformed the 51 feature sets and another contour type feature set with the pair-of-pairs data. |
|
T. S. Methven | Stereoscopic Viewing, Roughness and Gloss Perception Ph.D. thesis, School of Mathematical and Computer Sciences, Heriot-Watt University, 2013. Abstract To improve on the stimuli used in these earlier studies, advanced offline rendering techniques were employed to create images of complex, naturalistic, and realistically glossy 1/fβ noise surfaces. These images were rendered using multi-bounce path tracing to account for interreflections and soft shadows, with a reflectance model which observed all common light phenomena. Using these images in a series of psychophysical experiments, we first show that random phase spectra can alter the strength of perceived gloss. These results are presented alongside pairs of the surfaces tested which have similar levels of perceptual gloss. These surface pairs are then used to conclude that naïve observers consistently underestimate how glossy a surface is without the correct surface and highlight disparity, but only on the rougher surfaces presented. |
|
L. Qi | Measuring Perceived Gloss of Rough Surfaces Ph.D. thesis, School of Mathematical and Computer Sciences, Heriot-Watt University, 2012. Abstract We first investigated how the perceived gloss of a matte Lambertian surface varies with RMS roughness. Then we estimated the perceived gloss of moderate RMS height surfaces rendered using a gloss reflection model. We found that adjusting parameters of the gloss reflection model on the moderate RMS height surfaces produces similar levels of gloss to the high RMS height Lambertian surfaces. More realistic stimuli were modelled using improvements in the reflection model, rendering technique, illumination and viewing conditions. In contrast with previous research, a non-monotonic relationship was found between perceived gloss and mesoscale roughness when microscale parameters were held constant. Finally, the joint effect of variations in mesoscale roughness (surface geometry) and microscale roughness (reflection model) on perceived gloss was investigated and tested against conjoint measurement models. It was concluded that perceived gloss of rough surfaces is significantly affected by surface roughness in both mesoscale and microscale and can be described by a full conjoint measurement model. |
|
F. Halley | Perceptually Relevant Browsing Environments for Large Texture Databases Ph.D. thesis, School of Mathematical and Computer Sciences, Heriot-Watt University, 2012. Abstract |
|
A. D. F. Clarke | Modelling Visual Search for Surface Defects Ph.D. thesis, School of Mathematical and Computer Sciences, Heriot-Watt University, 2010. Abstract |
|
P. Shah | A Psychophysically-based Model for the Perceived Directionality of Textured Surfaces Ph.D. Thesis, School of Mathematical and Computer Sciences, Heriot-Watt University, 2010. Abstract Height maps of textured surfaces were rendered and animated in real-time with controlled illumination. Observers’ judgements of the directionality of surfaces were obtained by direct-ratio estimation, and either the method of pair-wise comparisons or the method of constant stimuli. The responses were used to derive a perceptual scale of directionality (perceived directionality) that could be related to physical properties of the surfaces. The thesis first investigates the relationships between each of two existing computational measures of directionality (Tamura’s variance and Davis’ variance) and human perception of directionality. This was done by using height maps captured from real surfaces, which were then manipulated to vary the computational measures of their directionality. From the psychophysical experiment, it was found that these two measures do not fully account for human perception of directionality, which must therefore be influenced by other properties of the textures. In order to investigate more fully the factors determining perceived directionality, synthetic random-phase surfaces defined by a mathematical model were used in the subsequent experiments. It was found that three properties of the magnitude spectrum of such surfaces significantly affect human perception of their directionality: angular variance, RMS roughness and central radial frequency. After determining these effects, the thesis proposes a measurement model of perceived directionality, which predicts human perception of directionality of a random-phase surface. |
|
M. S. A. Robb | Interactive real-time three-dimensional visualisation of virtual textiles Ph.D. Thesis, School of Mathematical and Computer Sciences, Heriot-Watt University, 2010. Abstract |
|
K. Emrith | Perceptual Dimensions for Surface Texture RetrievalPh.D. Thesis, School of Mathematical and Computer Sciences, Heriot-Watt University, 2008.Abstract This thesis presents a methodology for developing perceptually relevant surface texture retrieval systems. Generally such systems have been researched using image texture which has been captured under unknown or uncontrolled conditions (e.g. Brodatz). However, it is known that changes in illumination affect both the visual appearance of surfaces and the computational features extracted from their images. In contrast this thesis either uses surface information directly, or computes features obtained from images captured under controlled lighting conditions. Psychophysical experiments were conducted in which observers were asked to place texture samples into groups. Multidimensional Scaling was applied to the resulting similarity matrices to obtain a more manageable reduced perceptual space. A four dimensional representation was found to capture the majority of the variability. A corresponding feature space was created by linearly combining selected trace transform features. Retrieval was performed simply by determining the n closest neighbours to the query’s feature vector. An average retrieval precision of 60% was obtained in blind tests. Due to some confidentiality agreement, the content of this thesis will be made available at a later time. |
|
S. Padilla | Mathematical Models for Perceived Roughness of Three-Dimensional Surface Textures Ph.D. Thesis, Heriot-Watt University, 2008. Abstract Advanced computer graphics were used to model natural looking surfaces (1 / F &beta noise surfaces). These were generated and animated in real-time to enable observers to manipulate dynamically the parameters of the rendered surfaces. A method of adjustment was then employed to investigate the effects of changing the parameters on perceived roughness. From psychophysical experiments, it was found that the two most important parameters related to perceived roughness were the magnitude roll-off factor (&beta) and RMS height (&sigma) for this kind of surfaces. From the results of various extra experiments, an estimation method for perceived roughness was developed; this was inspired by common frequency-channel models. The final optimized model or estimator for perceived roughness in 1 / F &beta noise surfaces found was based on a FRF model. In this estimator, the first filter has a shape similar to a gaussian function and the RF part is a simple variance estimator. By comparing the results of the estimator with the observed data, it is possible to conclude that the estimator accurately represents perceived roughness for 1 / F &beta noise surfaces. Table of contents and individual chapters are available here. |
|
A. Spence | Calibrated and Uncalibrated Photometric Stereo for Surface Texture Acquisition Ph.D. Thesis, Heriot-Watt University, 2005. Abstract |
|
J. Dong | Three-dimensional Surface Texture Synthesis Ph.D. Thesis, Heriot-Watt University, 2003. Abstract We select a 2D texture synthesis algorithm which is then extended into multi-dimensional space to use the five surface representations as input. In this way, we develop five approaches for the synthesis of 3D surface textures. The synthesised results are compatible with computer graphics systems and can be used in real-time rendering applications. The five synthesis approaches are qualitatively assessed by employing psychophysical experiments and non-parametric statistics. The results show that the two low-dimensional methods, the Gradient and Eigen3, on average offer as good a performance as of any of the other methods and incur low computational cost. Table of contents and individual chapters are available here. |
|
C. Gullón | Height Recovery of Rough Surfaces from Intensity Images Ph.D. Thesis, Heriot-Watt University, February 2003. Abstract The most robust estimation is given by the Optimal Linear Filter. However this technique requires information about the surface topography, which is usually not available. Between the alternatives, the Benchmark technique gives more accurate reconstructions. A post-processing step which can be used to improve the surface estimate is presented. This minimises the brightness error using an iterative approach. When the Linear Photometric Stereo method is combined with the post-processing step, its performance is similar to that of the Benchmark technique, despite requiring one less image. However the Linear Photometric Stereo algorithm is restricted to constant albedo surfaces. The choice of the most appropriate method is determined by the application requirements. Table of contents and individual chapters are available here. |
|
J. Wu | Rotation Invariant Classification of 3D Surface Texture Using Photometric Stereo Ph.D. Thesis, Heriot Watt University 2003. Abstract The classification results using new-developed photometric stereo real texture database shown that combining 2D gradient and albedo data improves the classification’s performance to provide a successful classification rate of 99% Table of contents and individual chapters are available here. |
|
J. A. V. Pfeiffer | Directional compensation for sidescan sonar images Ph.D. Thesis, Heriot Watt University 2003. |
|
G. McGunnigle | The Classification of Textured Surfaces Under Varying Illuminant Direction Ph.D. thesis, Heriot-Watt University 1998. Abstract Table of contents and individual chapters are available here. |
|
M. J. Chantler | The Effect of Varying Illuminant Direction on Texture Classification Ph.D. thesis, Dept. Computing and Electrical Engineering, Heriot-Watt University, August 1994. Abstract The responses of three sets of texture measures are analysed using a test set of isotropic and directional textures. The results show that the feature measures’ outputs are affected by changes in illuminant direction. These changes are also shown to significantly increase the error rates of statistical classifiers implemented using the three feature sets. Normalisation of images is shown to reduce the error rates in some cases. The frequency domain model of image texture is further developed using empirical data and the resulting model used to design a set of tilt-compensation filters. These filters are used to pre-process images to reduce the effects of changes in the angle of tilt of the illuminant. Application of the filters to the test image set reduced the classification errors associated with directional textures. Table of contents and individual chapters are available here. |
Author |
Description
|
Download |
I.S. Bothwick | The Effect of Ensonification direction on seabed Images and Classification MSc Thesis, September 1998, Dept. of Computing and Electrical Engineering |
|
Carlos Lopez | Novel image processing of 3D textures MSc Thesis, Heriot Watt University, September 2003Abstract A new invariant-rotation texture operator, known as LBPROT (Local Binary Pattern Rotation-Invariant), has been recently developed by M. Pietikäinen, T. Ojala and Z. Xu. It has demonstrated much better performance at classifying textures than the well-known CSAR (Circular-Symmetric Autoregressive Random Field). This paper extends the experiments carried out then, and boards an alternative series of experiments in order to find out further information regarding LBPROT operator’s behaviour.Among the experiments performed, an analysis of the operator’s variability before distinct samples of the same texture under equal illumination conditions was accomplished. Furthermore, a research aiming at understanding the operator’s response when applied to different directionality features is widely presented. Moreover, some extra experiments utilize the operator output distribution to classify textures by using the G Statistic log-likelihood pseudo-metric. Finally, all these investigations are assessed leading to a series of interesting results which are discussed in dept. |
|
Ivan Rabascall | Uncalibrated Photometric Stereo for 3D Surface Texture Recovery Research Memorandum RM/02/02, May 2003, School of Mathematical & Computer SciencesAbstract This dissertation presents the method of uncalibrated photometric stereo for estimating the surface normal and the reflectance field without a priori knowledge of the light-source direction or the light-source intensity.In this method, assuming only that the object’s surface is Lambertian, the surface normal, and the surface reflectance, the light-source direction, and the light-source intensity can be determined simultaneously. |
Related PhDs
|