Important Short Questions and Answers: 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 a pictorial representation or graphical representation of objects in a computer.

2. Define refresh buffer/frame buffer.

The memory area where in picture definition is stored is called Refreshbuffer. This memory area holds the set of intensity values for all the screen points. On a black and white system with one bit per pixel, the frame buffer is called a bitmap.

3. What is pixel?

Each screen point in a monitor is called a pixel/pel. It is also called picture element.

4. Define aspect ratio.

It is a property of video monitors. This number gives the ratio of vertical points to horizontal points necessary to produce equal-length lines in both directions on the screen.

5. What is Output Primitive?

Basic geometric structures that describe a scene are referred to as Output Primitives. Points and straight lines segments are the simplest geometric components of pictures. Additional output primitives that can be used to construct a picture include circles and other conic sections, quadric surfaces, spline curves and surfaces, polygon color areas, and character strings.

6. What is DDA?

The Digital Differential Analyzer is a scan-conversion line algorithm based on calculating either difference in y-coordinate (dy) or difference in x-coordinate. We sample the line at unit intervals in one coordinate and determine corresponding integer values nearest the line path for the other coordinate.

7.What are the disadvantages of DDA algorithm?

Round-off error in successive additions of the floating-point increment can cause the calculated pixel positions to drift away from the true line path for long line segments.

Rounding operations and floating-point arithmetic in procedure are still time-consuming.

8. What is attribute parameter?

Any parameter that affects the way a primitive is to be displayed is referred to as an attribute parameter.

9. What are the basic line attributes?

Basic attributes of a straight line segment are its type, its width, and its color. 10. What is meant by aliasing?

The distortion of information due to low frequency sampling (Under sampling) is called aliasing. We can improve the appearance of displayed raster lines by applying antialiasing methods that compensate for the under sampling process.

11. Define Translation.

A translation is applied to an object by repositioning it along a straight line path from one coordinate location to another. We translate a two-dimensional point by adding translation distances, tx and ty, to original coordinate position (x, y) to move the point to a new position (x', y'). x' = x + tx, y' = y + ty. The translation distance pair (tx, ty ) is called a translation vector or shift vector.

12. Define Rotation.

A 2-D rotation is applied to an object by repositioning it \along a circular path in the xy plane.

13. Define Scaling.

A scaling transformation alters the size of an object. This operation can be carried out for polygons by multiplying the coordinate values (x,y) of each vertex by scaling factors sx and sy to produce the transformed coordinates ( x', y' ). x' = x. sx, y' = y. sy.

14. Define Reflection.

A Reflection is a transformation that produces a mirror image of an object. The mirror image for a 2D reflection is generated relative to an axis of reflection by rotating the object 180 degree about the reflection axis.

15. Define Shear.

A transformation that distorts the shape of an object such that the transformed shape appears as if the object were composed of internal layers that had been caused to slide over each other is called a shear.

16. Define Window.

A world-coordinate area selected for display is called a window

17. Define view port.

An area on a display device to which a window is mapped is called a view port.

18. What is viewing transformation?

The mapping of a part of a world-coordinate scene to device coordinates is referred to as viewing transformation.

19. Define Clipping.

Any procedure that identifies those portions of a picture that are either inside or outside of a specified region of space is referred to as a clipping algorithm or simply clipping. The region against which an object is clipped is called a clip window.

20 What are the types of Clipping?

Point clipping

Line clipping

Area clipping

Curve clipping

Text clipping

21.What is the purpose of presentation graphics?

Presentation graphics is used to produce illustrations for reports or to generate 35-mm slides or transparencies for use with projectors. Presentation graphics is commonly used to summarize financial, statical, mathematical, scientific, and economic data for research reports, managerial reports, consumer information bulletins, and other types of reports.

22. What is frame buffer?

Picture definition is stored in a memory area called frame buffer or refresh buffer.