Browsing by Subject "Computer graphics."

Now showing 1 - 20 of 59

Open Access
3D hair design and key frame animation in real time
(2008) Başarankut, Barkın
Computer generated animations of humans, animals and all other kinds of objects have been studied extensively during the last two decades. The key for creating good animations has been to correctly imitate the behaviors of real objects and reflect these into computer generated images. With the rapid development of computer technology, creating realistic simulations has become possible, and the most striking components of these realistic animations happen to be the most dynamic (moving) parts; hair, in the case of human animations. With the development of high quality hair animations, the concern is not only creating physically correct animations, but also controlling these animations. An implementation of a key frame hair animation creation system, supported by a hair design tool, helping to model and animate hair easily, and provide these functionalities in real time is the aim of the proposed system. This work reviews several hair animation and sketching techniques, and proposes a system that provides a complete level of control (capable of controlling even the individual hair strands) of key frame animation and hair design in real time.
Open Access
3D hair sketching for real-time hair modeling and dynamic simulations
(2008) Aras, Rıfat
Hair has been an active research area in computer graphics society for over a decade. Different approaches have been proposed for different aspects of hair research such as modeling, simulating, animating and rendering. In this thesis, we introduce a sketch-based tool making use of direct manipulation interfaces to create hair models and furthermore simulate the created hair models under physically based constraints in real-time. Throughout the thesis, the created tool will be analyzed with respect to different aspects of the problem such as hair modeling, hair simulation, hair sketching and hair rendering.
Open Access
3D mesh animation system targeted for multi-touch environments
(2009) Ceylan, Duygu
Fast developments in computer technology have given rise to different application areas such as multimedia, computer games, and Virtual Reality. All these application areas are based on animation of 3D models of real world objects. For this purpose, many tools have been developed to enable computer modeling and animation. Yet, most of these tools require a certain amount of experience about geometric modeling and animation principles, which creates a handicap for inexperienced users. This thesis introduces a solution to this problem by presenting a mesh animation system targeted specially for novice users. The main approach is based on one of the fundamental model representation concepts, Laplacian framework, which is successfully used in model editing applications. The solution presented perceives a model as a combination of smaller salient parts and uses the Laplacian framework to allow these parts to be manipulated simultaneously to produce a sense of movement. The interaction techniques developed enable users to carry manipulation and global transformation actions at the same time to create more pleasing results. Furthermore, the approach utilizes the multi-touch screen technology and direct manipulation principles to increase the usability of the system. The methods described are experimented by creating simple animations with several 3D models; which demonstrates the advantages of the proposed solution.
Open Access
3D model compression using image compression based methods
(2007) Köse, Kıvanç
A Connectivity-Guided AdaptiveWavelet Transform (CGAWT) based mesh compres- sion algorithm is proposed. On the contrary to previous work, the proposed method uses 2D image processing tools for compressing the mesh models. The 3D models are ¯rst transformed to 2D images on a regular grid structure by performing orthogonal projections onto the image plane. This operation is computationally simpler than pa- rameterization. The neighborhood concept in projection images is di®erent from 2D images because two connected vertex can be projected to isolated pixels. Connectiv- ity data of the 3D model de¯nes the interpixel correlations in the projection image. Thus the wavelet transforms used in image processing do not give good results on this representation. CGAWT is de¯ned to take advantage of interpixel correlations in the image-like representation. Using the proposed transform the pixels in the detail subbands are predicted from their connected neighbors in the low-pass subbands of the wavelet transform. The resulting wavelet data is encoded using either \Set Parti- tioning In Hierarchical Trees" (SPIHT) or JPEG2000. SPIHT approach is progressive because di®erent resolutions of the mesh can be reconstructed from di®erent partitions of SPIHT bitstream. On the other hand, JPEG2000 approach is a single rate coder. The quantization of the wavelet coe±cients determines the quality of the reconstructed model in JPEG2000 approach. Simulations using di®erent basis functions show that lazy wavelet basis gives better results. The results are improved using the CGAWT with lazy wavelet ¯lterbanks. SPIHT based algorithm is observed to be superior to JPEG2000 based mesh coder and MPEG-3DGC in rate-distortion.
Open Access
Animated mesh simplification based on saliency metrics
(2008) Tolgay, Ahmet
Mesh saliency identifies the visually important parts of a mesh. Mesh simplification algorithms using mesh saliency as simplification criterion preserve the salient features of a static 3D model. In this thesis, we propose a saliency measure that will be used to simplify animated 3D models. This saliency measure uses the acceleration and deceleration information about a dynamic 3D mesh in addition to the saliency information for static meshes. This provides the preservation of sharp features and visually important cues during animation. Since oscillating motions are also important in determining saliency, we propose a technique to detect oscillating motions and incorporate it into the saliency based animated model simplification algorithm. The proposed technique is experimented on animated models making oscillating motions and promising visual results are obtained.
Open Access
Camera-based 3D interaction for handheld devices
(2010) Pekin, Tacettin Sercan
Using handheld devices is a very important part of our daily life. Interacting with them is the most unavoidable part of using them. Today’s user interface designs are mostly adapted from desktop computers. The result of this was difficulties of using handheld devices. However processing power, new sensing technologies and cameras are already available for mobile devices. This gives us the possibility to develop systems to communicate through different modalities. This thesis proposes some novel approaches, including finger detection, finger tracking and object motion analysis, to allow efficient interaction with mobile devices. As the result of my thesis, a new interface between users and mobile devices is created. This is a new way of interaction with the mobile device. It enables direct manipulation on objects. The technique does not require any extra hardware. The interaction method, maps an object’s motion (such as a finger’s or a predefined marker’s motion) to a virtual space to achieve manipulation which is moving in front of the camera. For Finger Detection, a new method is created based on the usage of the mobile devices and structure of thumb. A fast two dimensional color-based scene analysis method is applied to solve the problem. For Finger Tracking, a new method is created based on the movement ergonomics of thumb when holding the mobile device on hand. Extracting the three dimensional movement from the two dimensional RGB data is an important part of this section of the study. A new 3D pointer data and pointer image is created for usage with 3D input and 3D interaction of 3D scenes. Also direct manipulation for low cost is achieved.
Open Access
Chisio : a visual framework for compound graph editing and layout
(2007) Küçükkeçeci, Cihan
Graphs are data models, widely used in many areas from networking to biology to computer science. Visualization, interactive editing ability and layout of graphs are critical issues when analyzing the underlying relational information. There are many commercial and non-commercial graph visualization tools. However, overall support for compound or hierarchically organized graph representations is very limited. We introduce a new open-source editing and layout framework named Chisio for compound graphs. Chisio is developed as a free, easy-to-use and powerful academic graph visualization tool, supporting various automatic layout algorithms. It is written in Java and based on Eclipse’s Graphical Editing Framework (GEF). Chisio can be used as a finished generic compound graph editor with standard graph editing facilities such as zoom, scroll, add or remove graph objects, move, and resize. Object property and layout options dialogs are provided to modify existing graph object properties and layout options, respectively. In addition, printing or saving the current drawing as a static image and persistent storage facilities are supported. Saved graphs or GraphML formatted files created by other tools can be loaded into Chisio. Furthermore, a highlight mechanism is provided to emphasize subgraphs of users interest. The framework has an architecture suitable for easy customization of the tool for end-users’ specific needs as well. Also Chisio offers several layout styles from the basic spring embedder to hierarchical layout to compound spring embedder to circular layout. Furthermore, new algorithms are straightforward to add, making Chisio an ideal test environment for layout algorithm developers.
Open Access
Chisio Web : a web-based framework for customizable visualization of relational information
(2012) Sümer, Selçuk Onur
Graphs are widely used to represent complex relational information. Graph visualization is crucial for effective analysis of information. In simple graphs, nodes are generally considered as uniform-sized components and they cannot be nested. This is often not sufficient to visualize complex relationships, because relational information is often clustered or hierarchically organized into groups or nested structures. There exist many free, open source software in the field of web-based graph visualization. However, none fully supports compound or clustered graphs. Moreover, customization provided by such software is often limited to the basic visual properties of nodes and edges. It requires a lot of effort to build an advanced customization of visual properties and interactive functionality with these software. In this thesis, we introduce a free, open source, general-purpose, web-based graph visualization framework, named Chisio Web (ChiWeb). ChiWeb supports visualization, interactive editing and layout of both simple and compound graphs. ChiWeb is implemented in ActionScript language and based on Flare, which is an open source ActionScript library designed for data visualization. ChiWeb is specifically designed for easy customization with respect to visualization and functionality. ChiWeb can be used as a library to create a custom graph visualization with an advanced application behavior for particular needs of a specific domain. The elements and functionality that can be easily customized with ChiWeb are: visual styles, controls for interactive events such as node creation, key and mouse functionality, context menus, toolbars, and inspector windows. Furthermore, ChiWeb’s architecture allows easy integration of new graph layout algorithms.
Open Access
A circular layout algorithm for clustered graphs
(2009) Belviranlı, Mehmet Esat
Visualization of information is essential for comprehension and analysis of the acquired data in any field of study. Graph layout is an important problem in information visualization and plays a crucial role in the drawing of graph-based data. There are many styles and ways to draw a graph depending on the type of the data. Clustered graph visualization is one popular aspect of the graph layout problem and there have been many studies on it. However, only a few of them focus on using circular layout to represent clusters. We present a new, elegant algorithm for layout of clustered graphs using a circular style. The algorithm is based on traditional force-directed layout scheme and uses circles to draw each cluster in the graph. In addition it can handle non-uniform node dimensions. It is the first algorithm to properly address layout of the quotient graph while considering inter-cluster relations as well as intra-cluster edge crossings. Experimental results show that the execution time and quality of the produced drawings with respect to commonly accepted layout criteria are quite satisfactory. The algorithm has been successfully implemented as part of Chisio, version 1.1. Chisio is an open source general purpose graph editor developed by i-Vis (information visualization) Research Group of Bilkent University.
Open Access
Color graph representation for structural analysis of tissue images
(2010) Altunbay, Doğan
Computer aided image analysis tools are becoming increasingly important in automated cancer diagnosis and grading. They have the potential of assisting pathologists in histopathological examination of tissues, which may lead to a considerable amount of subjectivity. These analysis tools help reduce the subjectivity, providing quantitative information about tissues. In literature, it has been proposed to implement such computational tools using different methods that represent a tissue with different set of image features. One of the most commonly used methods is the structural method that represents a tissue quantifying the spatial relationship of its components. Although previous structural methods lead to promising results for different tissue types, they only use the spatial relations of nuclear tissue components without considering the existence of different components in a tissue. However, additional information that could be obtained from other components of the tissue has an importance in better representing the tissue, and thus, in making more reliable decisions. This thesis introduces a novel structural method to quantify histopathological images for automated cancer diagnosis and grading. Unlike the previous structural methods, it proposes to represent a tissue considering the spatial distribution of different tissue components. To this end, it constructs a graph on multiple tissue components and colors its edges depending on the component types of their end points. Subsequently, a new set of structural features is extracted from these “color graphs” and used in the classification of tissues. Experiments conducted on 3236 photomicrographs of colon tissues that are taken from 258 different patients demonstrate that the color graph approach leads to 94.89 percent training accuracy and 88.63 percent test accuracy. Our experiments also show that the introduction of color edges to represent the spatial relationship of different tissue components and the use of graph features defined on these color edges significantly improve the classification accuracy of the previous structural methods.
Open Access
Combinatorial reductions between graph partitioning by vertex separator and hypergraph partitioning problems for parallel and scientific computing applications
(2009) Kayaaslan, Enver
Colour as an effective design tool influences people’s emotions in interior spaces. Depending on the assumption that colour has an impact on human psychology, this study stresses the need for further studies that comprise colour and emotion association in interior space in order to provide healthier spaces for inhabitants. Emotional reactions to colour in a living room were investigated by using self report measure. Pure red, green and blue were chosen to be investigated as chromatic colours, whereas gray was the achromatic colour used as a control variable. The study was conducted at Bilkent University in Ankara, Turkey. Hundred and eighty people from various ages and academic departments participated in the study. Participants first watched a short video showing an overlook of a 3D model of a living room. Next, they were asked to match the distinct coloured living rooms with facial expressions of six basic emotions that covers anger, disgust, surprise, happiness, fear, sadness and in addition with neutral. The results of the study indicated that the most stated emotions associated for the room with red walls were disgust and happiness, while the least stated emotions were sadness, fear, anger, and surprise. Neutral and happiness were the most stated emotions for the room with green walls and anger, surprise, fear and sadness were the least stated ones. The most stated emotion associated for the room with blue walls was neutral, while the least stated emotions were anger and surprise. Neutral, disgust and sadness were the most stated emotions for the room with gray walls. Gender differences were not found in human emotional reactions to living rooms with different wall colours.
Open Access
Combined filtering and keyframe reduction for motion capture data
(2007) Önder, Onur
Two new methods for combined filtering and key-frame reduction of motion capture data are proposed. Filtering of motion capture data is necessary to eliminate any jitter introduced by a motion capture system. Although jitter removal is needed to obtain a more realistic animation, it may result in an oversmoothed motion data if it is not done properly. Key-frame reduction, on the other hand, allows animators to easily edit motion data by representing animation curves with a significantly smaller number of key frames. One of the proposed techniques achieves key frame reduction and jitter removal simultaneously by fitting a Hermite curve to motion capture data using dynamic programming. Another method is to use curve simplification algorithms on the motion capture data until the desired reduction is reached. In this research, the results of these algorithms are evaluated and compared. Both subjective and objective results are presented.
Open Access
Comparing designers' cognitive behaviors in geometry-based and parametric 3D modeling environments
(2014) Tünger, Çetin
Digital design area has been constantly developed by scientific studies, but it is observed that studies in this area have mostly focused on the technical aspects of the subject (i.e. development of new tools and courses). User, tool, and process are three fundamental elements of a digital design system, so there is a need for studies on users and processes as well as tools. This study was carried out to understand and compare the cognitive behaviors of designers in conventional geometry-based and parametric 3D modeling environments within the framework mentioned above. While the geometry-based modeling tools are based on creation and the modification of the geometry, parametric modeling environments include an algorithmic structure underlying the form generation process. The study utilized Rhino as a geometric tool and Grasshopper as a parametric 3D tool. Six design students participated in the study. The data was collected by protocol analysis method and analyzed with a content-oriented coding scheme developed in this study. Results indicated that the cognitive actions of designers were significantly different in geometric and parametric modeling environments.
Open Access
A context aware approach for enhancing gesture recognition accuracy on handheld devices
(2010) Yıldırım, Hacı Mehmet
Input capabilities (e.g. joystick, keypad) of handheld devices allow users to interact with the user interface to access the information and mobile services. However, these input capabilities are very limited because of the mobile convenience. New input devices and interaction techniques are needed for handheld devices. Gestural interaction with accelerometer sensor is one of the newest interaction techniques on mobile computing. In this thesis, we introduce solutions that can be used for automatically enhancing the gesture recognition accuracy of accelerometer sensor, and as a standardized gesture library for gestural interaction on touch screen and accelerometer sensor. In this novel solution, we propose a framework that decides on suitable signal processing techniques for acceleration sensor data for a given context of the user. First system recognizes the context of the user using pattern recognition algorithm. Then, system automatically chooses signal ltering techniques for recognized context, and recognizes gestures. Gestures are also standardized for better usage. In this work, we also present several experiments which show the feasibility and e ectiveness of our automated gesture recognition enhancement system.
Open Access
Cubist style rendering of 3D virtual environments
(2012) Arpa, Sami
Cubism, pioneered by Pablo Picasso and Georges Braque, was a breakthrough in art, influencing artists to abandon existing traditions. In this thesis, we present a novel approach for cubist rendering of 3D synthetic environments. Rather than merely imitating cubist paintings, we apply the main principles of Analytical Cubism to 3D graphics rendering. In this respect, we develop a new cubist camera providing an extended view, and a perceptually based spatial imprecision technique that keeps the important regions of the scene within a certain area of the output. Additionally, several methods to provide a painterly style are applied. We demonstrate the effectiveness of our extending view method by comparing the visible face counts in the images rendered by the cubist camera model and the traditional perspective camera. Besides, we give an overall discussion of final results and apply user tests in which users compare our results very well with Analytical Cubist paintings but not Synthetic Cubist paintings.
Open Access
Data-driven synthesis of realistic human motion using motion graphs
(2014) Dirican, Hüseyin
Realistic human motions is an essential part of diverse range of media, such as feature films, video games and virtual environments. Motion capture provides realistic human motion data using sensor technology. However, motion capture data is not flexible. This drawback limits the utility of motion capture in practice. In this thesis, we propose a two-stage approach that makes the motion captured data reusable to synthesize new motions in real-time via motion graphs. Starting from a dataset of various motions, we construct a motion graph of similar motion segments and calculate the parameters, such as blending parameters, needed in the second stage. In the second stage, we synthesize a new human motion in realtime, depending on the blending techniques selected. Three different blending techniques, namely linear blending, cubic blending and anticipation-based blending, are provided to the user. In addition, motion clip preference approach, which is applied to the motion search algorithm, enable users to control the motion clip types in the result motion.
Open Access
A dept perception aware pen-based 3D sketching system
(2012) Yıldız, Cansın
This thesis proposes a method that resembles a natural pen and paper interface to create curve based 3D sketches. The system is particularly useful for representing initial 3D design ideas without much effort. Users interact with the system by the help of a pressure sensitive pen tablet, and a camera. The input strokes of the users are projected onto a drawing plane, which serves as a paper that they can place anywhere in the 3D scene. The resulting 3D sketch is visualized emphasizing depth perception by implementing several monocular depth cues, including motion parallax performed by tracking user’s head position. Our evaluation involving several naive users suggest that the system is suitable for a broad range of users to easily express their ideas in 3D. We further analyze the system with the help of an architect to demonstrate the expressive capabilities of the system that a professional can benefit.
Open Access
Design of an interactive sequential graphic system on cyber-space
(2000) Atasoy, Berke
The aim of this study is to explore and discuss the possibility of an interactive sequential system on World Wide Web. It is an attempt to formulate a definition for a system, which utilises different mediums like text, image and audio in the standards of World Wide Web with a motive for generating a sequential art product in the cyber-space. The study discusses a software model, which offers a set of actions in which the user can participate in the development process of the system by creating and combining different media.
Open Access
Designing for web and for printed medium: a comparative study
(2001) Michalski, Jakub
A thesis comparing two methods of design; the web design and design prepared for the printed medium, covering the physical differences between the two, the methods and techniques of content presentation in both cases, as well, as the perception of the design from the reader’s point of view. Includes a case study.
Open Access
The digital fulcrum: consequences of computer technology on graphic design
(1998) Özkal, Özlem
Departing from prevalent use and visible influence of computers on graphic design field, this study basically endeavours to elucidate the current problematics of the digital design process. In this context, with an inspection on the nature of technology, and respectively the concepts that form and help to specify computers, it aims to arrive at conclusions considering the relationship of graphic design and computers to help construct an awareness towards technology and computers in the digital design process.