Page 61 - DCAP303_MULTIMEDIA_SYSTEMS

Unit 4: Image

self assessment notes
Choose the correct answer:

1. Regular rectangular mesh of cells called ........................ .
( a) images (b) pixels
( c) RAW files (d) None of these
2. With files stored by bitmap storage method are called .................... .

( a) images (b) pixels
( c) RAW files (d) None of these
3. ....................... are created by the software and join up the control points that the user has
drawn.
( a) Vector drawing (b) Bitmap storage
( c) Specific formats (d) None of these

4.3 three Dimensional (3D) Drawing and rendering

Drawing in 3D adds a third axis to the X and Y-axis used in 2D. The Z-axis allows you a third
dimension, to create objects with a 3-dimensional thickness, or shape. These shapes can be put
together to create either simple or complex objects, which are called models.

Rendering is the process of generating an image from a model (or models in what collectively
could be called a scene file), by means of computer programs. A scene file contains objects in
a strictly defined language or data structure; it would contain geometry, viewpoint, texture,
lighting, and shading information as a description of the virtual scene. The data contained in the
scene file is then passed to a rendering program to be processed and output to a digital image or
raster graphics image file. The term “rendering” may be by analogy with an “artist’s rendering”
of a scene. Though the technical details of rendering methods vary, the general challenges to
overcome in producing a 2D image from a 3D representation stored in a scene file are outlined as
the graphics pipeline along a rendering device, such as a GPU. A GPU is a purpose-built device
able to assist a CPU in performing complex rendering calculations. If a scene is to look relatively
realistic and predictable under virtual lighting, the rendering software should solve the rendering
equation. The rendering equation does not account for all lighting phenomena, but is a general
lighting model for computer-generated imagery. ‘Rendering’ is also used to describe the process
of calculating effects in a video editing file to produce final video output.
Rendering is one of the major sub-topics of 3D computer graphics, and in practice always connected
to the others. In the graphics pipeline, it is the last major step, giving the final appearance to the
models and animation. With the increasing sophistication of computer graphics since the 1970s,
it has become a more distinct subject.
Rendering has uses in architecture, video games, simulators, movie or TV visual effects, and
design visualization, each employing a different balance of features and techniques. As a product,
a wide variety of renderers are available. Some are integrated into larger modelling and animation
packages, some are stand-alone, some are free open-source projects. On the inside, a renderer is a
carefully engineered program, based on a selective mixture of disciplines related to: light physics,
visual perception, and mathematics and software development.
In the case of 3D graphics, rendering may be done slowly, as in pre-rendering, or in real time.
Pre-rendering is a computationally intensive process that is typically used for movie creation,
while real-time rendering is often done for 3D video games which rely on the use of graphics
cards with 3D hardware accelerators.

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