Computer Graphics

1.      Define Computer Graphics.

Computer Graphics remains one of the most existing and rapidly growing computer fields. Computer graphics may be defined as the pictorial representation or graphical representation of objects in a computer

2. Write short notes on video controller.

Video controller is used to control the operation of the display device.A fixed area of the system is reserved for the frame buffer and the video controller is given direct access to the frame buffer memory Here, the frame buffer can be anywhere in the system memory, and the video controller accesses the frame buffer to refresh the screen. In addition to the video controller, more sophisticated raster systems employ other processors as coprocessor sand accelerators to implement various graphics operations.

3. Write notes on Graphics controller?

An application program is input and stored in the system memory along with a graphics package. Graphics commands in the application program are translated by the graphics package into a display file stored in the system memory. This display file is then accessed by the display processor to refresh the screen. The display processor cycles through each command in the display file program once during every refresh cycle. Sometimes the display processor in a random-scan system is referred to as a display processing unit or a graphics controller

4.List out a few attributes of output primitives?

Attributes are the properties of the output primitives; that is, an attribute describes how a particular primitive is to be displayed. They include intensity and color specifications, line styles, text styles, and area-filling patterns. Functions within this category can be used to set attributes for an individual primitive class or for groups of output primitives.

5.What is vertical retrace of the electron beam?

In raster scan display at the end of one frame the electron beam returns to the left top corner of the screen to start the next frame is called vertical retrace of the electron beam.

6. Define persistence, resolution and aspect ratio.

Persistence is defined as the time it takes the emitted light from the screen to decay to one tenth of its original intensity.

The maximum number of points that can be displayed without overlap on a CRT is referred to as the resolution.

Aspect ratio is the ratio of the vertical points to horizontal points necessary to produce equal length lines in both directions on the screen.

7.What is horizontal and vertical retrace?

The return to the left of the screen after refreshing each scan line is called as the horizontal retrace.

Vertical retrace: At the end of each frame the electron beam returns to the top left corner of the screen to the beginning the next frame.

8.What is interlaced refresh?

Each frame is refreshed using two passes. In the first pass, the beam sweeps across every other scan line from top to bottom. Then after the vertical retrace, the beam traces out the remaining scan lines.

9. What is a raster scan system?

In a raster scan system the electron beam is swept across the screen, one row at a time top to bottom. As the electron beam moves across each row, the beam intensity is turned on and off to create a pattern of illuminated spots. Picture information is stored in a memory area called refresh buffer or frame buffer. Most suited for scenes with subtle shading and color patterns.