Exercise No. 1
Computer Graphics Application
Objectives:
1. To define computer graphics and introduce its various applications in different fields.
2. To consider a particular application wherein the students can apply computer graphics as a visualization tool.
Discussion:
Computer graphics provides methods to generate images using a computer. These include 2D/3D images, graphics, and image sequences that are generated on computer screens or displays, printers and other devices.
An image can represent a realistic scene from the real world, but graphics like histograms or pie charts as well as the graphical user interface of a software tool are also considered as images.
Application Fields
Graphical user interfaces (GUI) can be considered as an application of computer graphics. However, there are standard programming tools and APIs (Application Programming Interfaces) for the implementation of GUI. These tools make the generation of GUI easy for the programmers.
Advertising and art pictures are sometimes designed using the computer only. In particular, photos serve as a basis and are modified or changed with computer graphics techniques.
2D/3D visualisations are used in the representation of high-dimensional data collected in business, industry, economy and science. Other than simple representations like graphs of functions, pie or bar charts, suitable data analysis techniques, methods for visualising high- dimensional data are needed.
Animations that show dynamic aspects like the flow of currents or the change of weather phenomena belong to this class of applications of computer graphics. The generation of realistic images and sequences of images is the main application field of computer graphics.
CAD/CAM (Computer-Aided Design/ Computer-Aided Manufacturing) is used for the design and construction of objects like cars or chassis. The objects are designed using suitable computer graphics software and their geometry is stored in computers.
Simulators is used as flight or driving guide to simulate city driving where existing landscapes and cities need to be modelled in the computer. The possibilities of designing, modelling and visualising objects play an important role in computer graphics, but also the generation of realistic models and representations of objects based on measurement data.
Medical informatics is another very important application field of computer graphics where measurements are available in the form of X-ray images or data from computerised tomography and ultrasonic testing.
Computer games allow to navigate through scenes and to view the scenes from different angles.
Movies have fixed viewpoint as they are shown on TV or in cinemas, that is, the choice of the viewpoint is not possible anymore once the movie has been produced. In order to view a scene from a viewpoint different from the cameras, the 3D scene is reconstructed using image processing methods exploiting the information coming from the different perspectives of the cameras.
Virtual reality is where the user should be able to move and act more or less freely in a virtual 3D world.
Augmented reality is where the real world is enriched by additional information in the form of text or virtual objects.
From a real scene to an image
The various application examples of computer graphics demonstrate that a large variety of different problems and tasks must be solved within computer graphics. Figure 1.1 illustrates crucial steps that are needed in order to generate an image from a real or virtual scene.
Figure 1.1 From a scene to an image
As a first step, the objects in the scene in Figure 1.1(a) have to be modelled with the techniques and methods provided by a computer graphics tool. In general, these models will not be exact copies of the real or virtual objects of the scene, but only approximations of them. Figure 1.1(b) illustrates this problem of approximation by assuming that the computer graphics tool is very restricted and the bowl in the real scene can only be approximated by a semisphere.
The modelled objects usually cover a much larger region than the part that is visible for the virtual viewer from his viewpoint. Taking the viewer’s position and the direction of his view into account, a 3D region must be defined that determines which objects might be visible for the viewer (see Figure 1.1(c)). The computation of which objects belong completely or at least partly to this region is called clipping or, more specifically, 3D-clipping.
The visible objects in the clipping region need to be projected onto a 2D plane in order to obtain a flat pixel image as shown in Figure 1.1(d) that can be printed out or shown on a computer screen.
The whole process of generating a pixel image from a 3D virtual scene is called rendering. The successive composition of the single techniques that are roughly outlined in Figure 1.1 is also referred to as the rendering pipeline.
Activity 1-1: Based on the given application fields above, identify existing software that is now being used. Give at least one for each field. Describe shortly the identified software.
Altia provides graphical user interface tools that allow GUI creation, usability testing and code generation. Altia Design is a GUI builder and User Interface design tool for laying out custom GUI’s. They offer expert user interface design and GUI development services to help plan, prototype and implement your next GUI design.
Adobe Photoshop is a graphics editing program developed and published by Adobe Systems. It has been considered essential software for graphic design and excellent tool for editing photos.
Adobe Flash or Macromedia Flash is a multimedia and software platform used for authoring of vector graphics, animation, games and rich internet applications that can be viewed, played and execute in Adobe Flash player. Flash manipulates vector and raster graphics to provide animation of text, drawings, and still images.
Autodesk focuses on 3D design software for use in architecture, engineering, construction, media and entertaiment industries. Autodesk became best know for AutoCAD but now develops a broad range of software for design, engineering, and entertaiment as well as a line of software for consumers.
Activity 1-2: Assume you want to develop application software in monitoring stock market. Give a particular scenario wherein the computer graphics will show the trend of the monitored stock market.
Activity 1-3: Assume you want to develop a drawing tutorial for kinder students. Give a particular scenario wherein the computer graphics will show how to draw circle and rectangle. 