COMPUTER GRAPHICS AND VISUALISATION

The appliances of methods in computer graphics span from simulations, computer aided education to digital photography and entertainment. Some fundamental problems of computer graphics and visualisations are investigated, such as the complexities of illumination in virtual scenes, different aspects of modeling and animating virtual environments and processing the main aspects which differ various imaging formats. Particular methods and technologies related to computer graphics and visualization are developed. The insight is given to how graphics can be generated and manipulated, and computed based to some specific applications. A large number of novel visualisation techniques are summarized.

Geometric primitives are a staple of computer graphics. They provide artists with shapes that are easy to understand and create, yet they can be easily combined and modified into more complex structures. A new 2D geometric primitive is derived represent¬ing a smooth curved shape that blends two circles of any radii, and is controlled with a few parameters which have immediate geometric interpretations. The applications of shapes, surfaces and curves in computer graphics are introduced in the initial six chapters of the book. Also, the concept of curve segment is introduced after relaxing the definition of digital straight segment and it is used to decompose a digital curve into a sequence of curve segments.

3D scene modeling has long been a fundamental problem in computer graphics. With the popularity of consumer-level RGB-D cameras, there is a growing interest in digitizing real-world indoor 3D scenes. However, modeling indoor 3D scenes remains a challenging problem because of the complex structure of interior objects and poor quality of RGB-D data acquired by consumer-level sensors. Various methods have been proposed to tackle these challenges. An overview of recent advances in indoor scene modeling techniques is presented in Chapter 7 of the book, as well as public datasets and code libraries which can facilitate experiments and evaluation.

The following eight chapters of the book present various visualization techniques to improve practical appliances of computer graphics, such as surface waves of the jet, electrical resistance tomography, videoconferencing and cranio-maxillofacial (CMF) surgery. An overview of image enhancement techniques based on the use of Particle Swarm Optimization is presented in the final chapter of the book.

A variety of mappings between a sphere and a disc and between a disc and a square, as well as combinations of both, are used in computer graphics applications, resulting in mappings between spheres and squares. Many options exist for each type of mapping; to pick the right methods for a given application requires knowledge about the nature and magnitude of mapping distortions.

An overview of forward and inverse mappings between a unit sphere, a unit disc, and a unit square is provided. Quality measure¬ments relevant for computer graphics applications are derived from tools used in the field of map projection, and a comparative analysis of the mapping methods is given.

A novel, direct ray-tracing method for rendering Catmull-Clark subdivision surfaces is presented. This method resolves an intersection with Bezier patches without performing of polygon tessellation as done in most traditional renderers.

The instability analysis of the liquid jet issuing into ambient air was conducted with an emphasis placed upon the evolution of surface waves of the jet. An experiment was designed to visualize the microscopic morphology on the surface of a liquid jet. A spectral method was proposed to measure wavelength from the obtained jet images.

An iterative back projection method (i-BP) has been developed to improve the resolution of reconstructed images produced by electrical resistance tomography (ERT). This solution is based on an iterative calculation of the electrical fields and it is possible to reconstruct clearer images than those reconstructed by the conventional back projection method without divergence. Numeri¬cal simulations and experiments using a simple model are performed in this study. The numerical simulations show that clear images are reconstructed both near the wall and at the center by i-BP.

Face-to-face videoconferencing system is considered that uses a Kinect camera at each end of the link for 3D modeling and an ordinary 2D display for output. The Kinect camera allows a 3D model of each participant to be transmitted; the (assumed static) background is sent separately. Furthermore, the Kinect tracks the receiver’s head, allowing our system to render a view of the sender depending on the receiver’s viewpoint. The resulting motion parallax gives the receivers a strong impression of 3D viewing as they move, yet the system only needs an ordinary 2D display.

The recent development of light field cameras has received growing interest, as their rich angular information has potential benefits for many computer vision tasks. A novel method is introduced to obtain a dense disparity map by use of ground control points (GCPs) in the light field. Previous work optimizes the disparity map by local estimation which includes both reliable points and unreliable points. To reduce the negative effect of the unreliable points, the disparity at non-GCPs from GCPs is predicted. The method performs more robustly in shadow areas than previous methods based on GCP work, since color information and local disparity is combined.

A method for synthesizing a stroboscopic image of a moving sports player from a hand-held camera sequence is developed. This method has three steps: synthesis of background image, synthesis of stroboscopic image, and removal of player’s shadow. In synthesis of background image step, all input frames masked a bounding box of the player are stitched together to generate a background image. In synthesis of stroboscopic image step, the background image, the input frame, and a mask of the player synthesize a stroboscopic image.

Volume visualization has numerous applications that benefit different knowledge domains, such as biology, medicine, meteorology, oceanography, geology, among others. With the continuous advances of technology, it has been possible to achieve considerable rendering rates and a high degree of realism. Visualization tools have currently assisted users with the visual analysis of complex and large datasets. Marching cubes is one of the most widely used real-time volume rendering methods. A methodology is developed for speeding up the marching cubes algorithm on a graphics processing unit and discusses a number of ways to improve its performance by means of auxiliary spatial data structures.

In the field of cranio-maxillofacial (CMF) surgery, surgical simulation is becoming a very powerful tool to plan surgery and simulate surgical results before actually performing a CMF surgical procedure. Reliable prediction of facial soft tissue changes is in particular essential for better preparation and to shorten the time taken for the operation. A surgical simulation system is provided to predict facial soft tissue changes caused by the movement of bone segments during CMF surgery.

A simple-yet-effective method for isotropic meshing relying on Euclidean distance transformation based centroidal Voronoi tessellation (CVT) is presented. This approach improves the performance and robustness of computing CVT on curved domains while simultaneously providing high-quality output meshes.