Page 9 - DCAP313_LAB_ON_COMPUTER_GRAPHICS

Unit 1: Fundamentals of Computer Graphics

For a colour image, each pixel is described by a triple of numbers characterizing the intensity of Notes
red, green and blue. For example, pure red is (255, 0, 0) and purple is (255, 0, 255). The image is
represented by a isolated array of pixels, aliasing problems may occur. The most classical form
of aliasing is the jaggy aspect of lines. Ant aliasing techniques are thus required. In the case of
the line (See Figure 1.2), it consists in using intermediate gray levels to “smooth” the appearance
of the line. Another form of aliasing can be observed on television when people wear shirts with
a fine stripped texture. A flickering prototype is observed because the size of the pattern is on
the same order of magnitude as the pixel size.

Figure 1.2: A Line Without and with Anti-aliasing

1.1 Concept of Computer Graphics

The creation of, manipulation of, study of, and interaction with graphic representations of objects
and data using computers graphics is also called image synthesis.

Computer graphics comprises the creation and representation of simple graphical elements and
images, as well as modern techniques for rendering a virtual reality. To apply these techniques
correctly, one requires a basic understanding of the fundamental concepts in graphics.
The most important basic concept of computer graphics is pairing the technical background
and theory with practical examples and applications throughout. Its user-friendly approach
enables the reader to gain understanding through the theory at work, via the many example
programs provided.
One of the most common uses for computer graphics is the creation of an image that looks like
a photograph from real life, but portrays something we could not really take a picture of. For
example, we might want to create an animation for a movie that portrays an alien creature or
location, or we might want to create an architectural rendering to get an idea of what the final
building will look like. We will call this type of computer graphics photo-realistic. Normally
there is a significant amount of time available for creating these images, and so the techniques
often attempt to capture the properties of lights and surfaces as accurately as possible, at the
expense of time needed to compute the image.

Another common use for computer graphics is the creation of images very swiftly so that they
can be used in an interactive animation; the application of these algorithms that most people
are well-known with is computer games. As a user controls their nature, we want to create a
series of images very quickly (hopefully 30 per second or more) that respond to their inputs.
We will refer to this type of computer graphics as real-time, or interactive. We might want these
images to look as sensible as possible, but the fact of the situation is that if we have more time
to devote to computation, we can create better results. Thus, real-time computer graphics is
usually concerned with techniques for creating the best-looking picture possible with the very
short amount of time available between frames.
There are many other applications for computer graphics as well. We might be interested in
automating a complex picture that we could make by hand for convenience, or we might be
interested in creating an image that is abstract or random in nature. In fact, there are many
applications of computer graphics that fall somewhere in-between the two extremes presented

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