cg2401 2marks for units

5/21/2018 Cg2401 2marks for Units

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CS 72-COMPUTER GRAPHICS 2 MARKS WITH ANSWERS

Prepared by:Mrs.R.J.Alice Nineta,AP/IT

DEPARTMENT OF INFORMATION TECHNOLOGY

COMPUTER GRAPHICS- 2 MARK QUESTIONS WITH ANSWERS

SEM/YEAR-07/IV

UNITI

2D PRIMITIVES

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. Name any four input devices.

Four input devices are keyboard, mouse, image scanners, and trackball.

3. What is resolution?

The maximum number of points that can be displayed without overlap on a CRT is

referred to as the resolution.

4. Write the types of clipping?

Point clipping, line clipping, area clipping, text clipping and curve clipping.

5. Define pixel?

Pixel is shortened forms of picture element. Each screen point is referred to aspixel or pel.

6. What is frame buffer?

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


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7. What is point in the computer graphics system?

The point is a most basic graphical element & is completely defined by a pair of

user coordinates (x, y).

8. Write short notes on lines?

A line is of infinite extent can be defined by an angle of slope q and one point on

the line P=P(x,y). This can also be defined as y=mx+C where C is the Yintercept.

9. Define Circle?

Circle is defined by its center xc, yc and its radius in user coordinate units. The

equation of the circle is (x-xc) + (y-yc) = r2.

10. What are the various attributes of a line?

The line type, width and color are the attributes of the line. The line type includes

solid line, dashed lines, and dotted lines.

11. What is Transformation?

Transformation is the process of introducing changes in the shape size and

orientation of the object using scaling rotation reflection shearing & translation etc.

12. What is translation?

Translation is the process of changing the position of an object in a straight-line

path from one coordinate location to another. Every point (x , y) in the object must

under go a displacement to (x|,y|). the transformation is: x = x + tx ; y = y+ty

13. What is rotation?

A 2-D rotation is done by repositioning the coordinates along a circular path, in the

x-y plane by making an angle with the axes. The transformation is given by:

X = r cos (q + f) and Y = r sin (q + f).

14. What is scaling?


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A 2-D rotation is done by repositioning the coordinates along a circular path, in the

x-y plane by making an angle with the axes. The transformation is given by:

X = r cos (q + f) and Y|= r sin (q + f).

15. What is shearing?

The shearing transformation actually slants the object along the X direction or the

Y direction as required. ie; this transformation slants the shape of an object along a

required plane.

16. What is reflection?

The reflection is actually the transformation that produces a mirror image of an

object. For this use some angles and lines of reflection.

17. Distinguish between window port & view port?

A portion of a picture that is to be displayed by a window is known as window

port. The display area of the part selected or the form in which the selected part is

viewed is known as view port.

18. Define clipping?

Clipping is the method of cutting a graphics display to neatly fit a predefined

graphics region or the view port

19. What is the need of homogeneous coordinates?

To perform more than one transformation at a time, use homogeneous coordinates

or matrixes. They reduce unwanted calculations intermediate steps saves time and

memory and produce a sequence of transformations.

20. Distinguish between uniform scaling and differential scaling?

When the scaling factors sx and sy are assigned to the same value, a uniform

scaling is produced that maintains relative object proportions. Unequal values for

sx and sy result in a differential scaling that is often used in design application

21. What is fixed point scaling?


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The location of a scaled object can be controlled by a position called the fixed

point that is to remain unchanged after the scaling transformation.

22. What is Zooming?

Zooming means enlarging a digital image to see it more clearly or make it easier to

alter. It allows the user to see more detail for a specific area of the image.

23. What is Rubber Banding?

Rubber Banding is another form of zooming. The user can use a mouse to

define two corners of a rectangle. The selected area can be copied to a clipboard,

cut, moved or zoomed.

24. What is an output primitive?

Graphics programming packages provide function to describe a scene in terms of

these basic geometric structures, referred to as output primitives.

25. List out the graphicsapplications

paint programs:Allow you to create rough freehand drawings. The images are

storedasbit mapsand can easily be edited.

illustration/design programs: Supports more advanced features than paint

programs, particularly for drawing curved lines. The images are usually

stored in vector-based formats. Illustration/design programs are often called

draw programs.

presentation graphics software : Lets you create bar charts,pie charts, graphics, and

other types of images for slide shows and reports. The charts can be based

on data imported from spreadsheet applications.

animationsoftware:Enables you to chain and sequence a series of images to

simulate movement. Each image is like aframein a movie.

CADsoftware:Enables architects and engineers to draft designs.
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desktop publishing :Provides a full set of word-processing features as well as

fine control over placement of text and graphics, so that you can create

newsletters, advertisements, books, and other types ofdocuments.

UNIT II

3D CONCEPTS

1. Define Projection?

The process of converting the description of objects from world coordinates

to viewing coordinates is known as projection. The process of displaying 3D into a

2D display unit is known as projection. The projection transforms 3D objects into a

2D projection plane

2. What are the steps involved in 3D transformation?

Modeling Transformation

Viewing Transformation

Projection Transformation

Workstation Transformation

3. What do you mean by view plane?

A view plane is nothing but the film plane in camera which is positioned andoriented for a particular shot of the scene.

4. List out the 3D Issues?

More Complicated Objects than 2D

More involved geometric transformations
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Viewing transformations much more complicated

Projection onto a two dimensional output display (usually)

Identification of Visible Surfaces

5. What you mean by parallel projection?

Parallel projection is one in which z coordinates is discarded and parallel

lines from each vertex on the object are extended until they intersect the view

plane.

6. What do you mean by Perspective projection?

Perspective projection is one in which the lines of projection are not parallel.

Instead, they all converge at a single point called the center of projection.

7. What is Projection reference point?

In Perspective projection, the lines of projection are not parallel. Instead,

they all converge at a single point called Projection reference point.

8. Define computer graphics animation?

Computer graphics animation is the use of computer graphics equipment

where the graphics output presentation dynamically changes in real time. This isoften also called real time animation.

9. What is two lining?

It is the process, which is applicable to animation objects defined by a

sequence of points, and that change shape from frame to frame.

10. Define frame?

One of the shape photographs that a film or video is made of is known as frame.

11. What is key frame?

One of the shape photographs that a film or video is made of the shape of an

object is known initially and for a small no of other frames called keyframe


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12. Define Random scan/Raster scan displays?

Random scan is a method in which the display is made by the electronic

beam which is directed only to the points or part of the screen where the picture is

to be drawn.

The Raster scan system is a scanning technique in which the electrons sweep

from top to bottom and from left to right. The intensity is turned on or off to light

and unlight the pixel.

13. What is bit map?

A bit map (often spelled "bitmap") defines a display space and the color for

eachpixelor "bit" in the display space. AGraphics Interchange Formatand aJPEGare

examples of graphic image file types that contain bit maps. A bit map does not

need to contain a bit of color-coded information for each pixel on every row. It

only needs to contain information indicating a new color as the display scans along

a row. Thus, an image with much solid color will tend to require a small bit map.

Because a bit map uses a fixed or raster graphicsmethod of specifying an

image, the image cannot be immediately rescaled by a user without losing

definition. A vector graphicsgraphic image, however, is designed to be quickly

rescaled. Typically, an image is created using vector graphics and then, when the

artist is satisfied with the image, it is converted to (or saved as) a raster graphic fileor bit map.

14. What is Pixel?

The pixel (a word invented from "picture element") is the basic unit of

programmable color on a computer display or in a computer image. Think of it as a

logical - rather than a physical - unit. The physical size of a pixel depends on how

you've set the resolution for the display screen. If you've set the display to its

maximum resolution, the physical size of a pixel will equal the physical size of the

dot pitch (let's just call it the dot size) of the display. If, however, you've set theresolution to something less than the maximum resolution, a pixel will be larger

than the physical size of the screen's dot (that is, a pixel will use more than one

dot). The specific color that a pixel describes is some blend of three components of

the color spectrum - RGB.
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15. What is RGB?

RGB (red, green, and blue) refers to a system for representing the colors to

be used on a computer display. Red, green, and blue can be combined in various

proportions to obtain any color in the visible spectrum. Levels of R, G, and B can

each range from 0 to 100 percent of full intensity. Each level is represented by the

range of decimal numbers from 0 to 255 (256 levels for each color), equivalent to

the range of binary numbers from 00000000 to 11111111, or hexadecimal00 to FF.

The total number of available colors is 256 x 256 x 256, or 16,777,216 possible

colors.

16. What is cathode ray tube (CRT)?

A cathode ray tube (CRT) is a specialized vacuumtube in which images areproduced when an electron beam strikes aphosphorescent surface. Most desktop

computer displays make useof CRTs. The CRT in a computer display is similar to

the"picture tube" in a television receiver.

A cathode ray tube consists of several basiccomponents, as illustrated below. The

electron gun generates anarrow beam of electrons. The anodes accelerate the

electrons.Deflecting coils produce an extremely low frequency electromagnetic field

that allowsfor constant adjustment of the direction of the electron beam.There are

two sets of deflecting coils: horizontal and vertical.(In the illustration, only one set

of coils is shown forsimplicity.) The intensity of the beam can be varied.

17. List out the methods used for smoothly joining two line segments?

Mitter joinby extending the outer boundaries of each of the two lines

until they meet.

Round joinby capping the connection between the two segments with a

circular boundary whose diameter is equal to the line width.

Bevel joinby displaying the line segments with butt caps and filling in

the triangular gap where the segment meet.

18. Define bundled attributes?

Individual attribute commands provide a simple and direct method for specifying

attributes when a single output device is used. When several kinds of output device
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are available at a graphics installation, it is convenient to set up a table for each

output device that lists set of attribute values that are to be used on that device to

display each primitive type. Attribute specified in this manner is known as bundled

attribute.

19. What is scan line algorithm?

One way to fill the polygon is to apply the inside test. i.e to check whether the

pixel is inside the polygon or outside the polygon and then highlight the pixel

which lie inside the polygon. This approach is known as scan-line algorithm..

20. What is a Line cap?

Line caps can be used to adjust the shape of the line ends to give a better

appearance. There are three types of line caps. Butt cap which has a square end,

round cap which has a semi circle end, projecting square cap which has one half of

the line width beyond the specified end points


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UNIT III

GRAPHICS PROGRAMMING

1. State the properties of Holographic images?

Holographic images are

not clear diagrams

3-dimensional

can also be recorded on materials other than photographic plates

records intensity of light and phase

created by coherent light using a laser beam

2. Define Fractals?

Fractals are regular objects with a high degree of irregular shapes. It is a lossy

compression technique but it doesnt change the shape of the image. Fractals are

decompressed images that result from a compression format

3. Explain Fractal Compression?

Fractal Compression is based on image content i.e., it is based on similarity of

patterns within an image. The steps in Fractal compression are

a digitized image is broken into segments

the individual segments are checked against a library of fractals

the library contains a compact set of numbers called iterated function

these system codes will reproduce the corresponding fractal

4. State the applications of Document Imaging?

Document Imaging is used in organizations such as

Insurance agencies


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Law offices

Country and State Governments

Federal Government

Department of Defence (DOD)

5. Define Compression Efficiency?

Compression Efficiency is defined as the ratio in bytes of an uncompressed image

to the same image after compression.

6. What is Image Processing?

Image Processing refers to processing a digital image using a digital computer. An

image processing system will alter the contents of the image. It involves ImageRecognition, Image Enhancement, Image Synthesis and Image Reconstruction.

7. Explain Image Calibration?

The overall image density is calibrated. In Image calibration the image pixels are

adjusted to a predefined level.

8. What is Grayscale Normalization?

The overall grayscale of an image or picture is evaluated to determine if it isskewed in one direction and if it needs correction.

9. What is Frame Averaging?

The intensity level of the frame is averaged to overcome the effects of very dark or

very light areas by adjusting the middle tones.

10. What is Image Animation?

Images are displayed sequentially at controlled display speeds to provide image

animation. Image Animation is the basic concept of displaying successive images

at short intervals to give the perception of motion. Image Animation is a

technology developed by Walt Disney and brought to every home in the form of

cartoons.


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11. How Image Annotation is done?

Image Annotation can be performed in two ways

as a text file stored along the image.

as a small image stored with the original image.

12. State the resolution of Facsimile, Document Images and Photographic

Images?

Facsimile100 to 200 dpi

Document images300 dpi (dots/pixels per inch)Photographic images600 dpi

13. What is the compression technique used in Facsimile and Document

Images?

Facsimile - CCITT Group3

Document Images - CCITT Group4

14. What are the applications of Photographic Images?

Photographic images are used in Imaging Systems that are used for identification

such as

Security Badges

Fingerprint Cards

Photo Identification Systems

15. What is Raster graphics?

Raster graphics are digital images created or captured (for example, by scanning ina photo) as a set of samples of a given space. A rasteris a grid ofx and y coordinates

on a display space. (And for three-dimensional images, a z coordinate.) A raster

image file identifies which of these coordinates to illuminate in monochrome or

color values. The raster file is sometimes referred to as a bitmapbecause it contains

information that is directly mapped to the display grid.
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A raster file is usually larger than avector graphicsimage file. A raster file is usually

difficult to modify without loss of information, although there are software tools

that can convert a raster file into a vector file for refinement and changes.

Examples of raster image file types are: BMP, TIFF,GIF,andJPEGfiles.

16. Define computer graphics animation?

Computer graphics animation is the use of computer graphics equipment where the

graphics output presentation dynamically changes in real time. This is often also

called real time animation.

17. What is key frame?

One of the shape photographs that a film or video is made of the shape of an object

is known initially and for a small no of other frames called keyframe

18. What is pseudo animation?

Pseudo animation is creating a sequence of stills, photographing or video graphing

each still as one frame, and then later playing back the frames at a faster speed.

19. What is the normal speed of a visual animation?

Visual animation requires a playback of at least 25 frames per second

20. What is an intuitive interface?

The intuitive interface is one, which simulates the way a person would perform a

corresponding operation on real object rather than have menu command.

21. What is Sprite?

A Sprite is graphics shape in animation and games programs. Each sprite provided

in the system has its own memory area similar to but smaller than pixel RAM.

22. What is computer graphics realism?
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The creation of realistic picture in computer graphics is known as realism. It is

important in fields such as simulation, design, entertainments, advertising,

research, education, command, and control.

UNIT IV

RENDERING

1. What is meant by Rendering?

In 3D graphics rendering means the calculation of the final image from the scenethat includes models, textures, lights, special effects and cameras. The final image

will be 2D image made of pixels. Utilizing materials, lighting techniques, and

renderers settings one can render multitude of different images from a single 3D

scene.

2. Types of Rendering?

Realistic rendering

Clay Rendering

Wire Rendering

3. Purpose of Wire Rendering.

The purpose of wire rendering is to reveal the polygon structure of the model. Wire

rendering displays only edges of the polygons. Wire render and clay render are

often combined.

4. Write the syntax of smooth shading.

Syntax:

glshadeModel(GL_smooth);

It calculates the color at each vertex.

It produces much better image.


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It computes during scan conversion.

5. List out the drawbacks of shadow mapping.

Aliasing especially when using small shadow maps.

The scene geometry must be rendered once per light inorder to generate the

shadow map for a spot light.

6. What are the two types of textures.

Two types of textures are:

Bitmap

Procedural

7. What are the stages of rendering?

Loading the shadow buffer

Rendering the scene

8. Write the function of bitmap textures.

The function texture (s,t) accesses in the code:

color3 texture(Float s,Float t)

{

return txtr[(int)(s*c)][(int)(t*R)]

}

where colr3 holds an RGB tuple.

9. List the advantages of phong shading.


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In Phong shading the direction of normal vector varies smoothly from

point to point and more closely approximates that of an underlying smooth

surface.

More realistic rendering are produced.

The production of specular highlights is much more faithful than with

Gouraud shding.

10.Define Texture mapping?

One of the most important tool in computer graphics is texture mapping.Texture

mapping applies an image to a surface.It allows a simple polygon to appear to have

a complex surface texture.

11. List the advantages of flat shading?

inexpensive to compute

Appropriate for objects with flat surface

Less pleasant for smooth surfaces.

12. What are the methods of shading?

Circulism

Blended Circulism

Dark Blacks

Loose cross Hatching

Tight cross Hatching

Powder Shading

13. What is the UDC technique


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UDC stands for User Defined Character set.It is graphics animation trick which

used in early microcomputer system.

14. List the advantages of shadow mapping?

No knowledge or processing of the scene geometry is required.

Only a single texture is required to hold shadowing information for each

light.

Avoids the high fill requirement of shadow volume.

15. What is computer graphics realism

The creation of realistic picture in computer graphics is known as realism.It is

important in fields such as

simulation,design,entertainments,advertising,research,education,command and

control.

16.Define shadow volume.

The stencil buffer is used to find the interaction between the polygons in

the scene and the shadow volume.

This technique treat the shadows cast by objects as polygonal volumes .

17.What are the steps in rendering 3D texture.

Create the 3D texture

Create Texture Coordinates

Enable Texturing

18.What is the purpose of stencil buffer in shadowing?

The stencil buffer is used to compute which parts of the objects in the scene

are in the shadow volume.It uses a non zero winding rule technique.For every


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pixel in the scene, the stencil value is incremented as it crosses a shadow boundary

going into the shadow volume and decrement as it crosses a boundary going out.

19.What is texturing?

A texture image is a rectangular array of pixel data.Applying textures a

graphical object to achieve a more interesting image or add information to the

image without computing additional geometry.The key idea is to apply additional

information to your image is computed and displayed.

20.What is shadow mapping?

Shadow mapping is just one of many different ways of producing shadows in your

graphics applications each with its own advantages and disadvantages

UNIT V

FRACTALS

1. What is Fractals?

A Fractal is an object whose shape is irregular at all scales.

2. What is a Fractal Dimension?

Fractal has infinite detail and fractal dimension. A fractal imbedded in n

dimensional space could have any fractional dimension between 0 and n.

The Fractal Dimension D= LogN / Log S

Where N is the No of Pieces and S is the Scaling Factor.

3. What is marble texture?

Marble shows veins of dark and light material that have some regularity but that

also exhibit strongly chaotic irregularities..


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4. What is solid texture?

Solid texture is sometimes called as 3D texture.We view an object as being carved

out of the texture material such as marble or wood.The texture is represented by a

fuction texture(x,y,z)that produces an (r,g,h) color value at every point in space.

5. What is Koch curve?

The Koch curve can be drawn by dividing line into 4 equal segments with scaling

factor 1/3. and middle 2 segments are so adjusted that they form adjustment sides

of an equilateral triangle.

6. What is turtle graphics program?

The turtle program is a Robert that can move in 2 dimensions and it has a pencil

for drawing. The turtle is defined by the following parameters. g. Position of the

turtle (x, y) h. Heading of the turtle 0 the angle from the x axis.

7. What is graftals?

Graftals are applicable to represent realistic rendering plants and trees. A tree is

represented by a String of symbols 0, 1, [, ]

8. What is a Particle system?

A particle system is a method for modeling natural objects, or other irregularly

shaped objects, that exhibit fluid-like properties. Particle systems are suitable for

realistic rendering of fuzzy objects, smoke, sea and grass.

9. Give some examples for computer graphics standards?

COREThe Core graphics standardGKS -- The Graphics Kernel system

PHIGSThe Programmers Hierarchical Interactive Graphics System.

GSXThe Graphics system extension m.

NAPLPSThe North American presentation level protocol syntax.


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10. What is geometric fractal?

Geometric fractal is a fractal that repeats self similar patterns over all scales.

11.What is random fractal?

The patterns in the random fractals are no longer perfect and the random defects at

all scale.

12. Write about drawing scenes using OPENGL.

OpenGL draws scenes by combining the ambient ,diffuse and specular

components of light that illuminate a vertex of an object.

It uses the phong model to calculate the specular light component.

13. Give the types of textures.

There are two principle kinds of textures used.

With a image texture a 2D image is pasted onto each surface of the object.

With a solid texture the object is considered to be carved out of a block of

solid material that itself has texturing.The ray traces reveals the color of the

texture at each point on the surface of the object.

14. What is the purpose of scene class?

The scene class can read a file in the SDL language and build a list of objects in a

scene.This class can be used for ray tracing as well as to build scenes using the

following code:

Scene scn;

read(myScene.dat);

15. Define a Peano curve.

A curve can in fact fill the plane and therefore have a dimension of 2 such curves

are called Peano curve.


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16.Define Random Factrals?

The term fractal usually refers to sets which, in some sense, have a self-similar

structure. Indeed, some form of self-similarity is common in random sets, in

particular those arising from stochastic processes. Therefore studying fractal

aspects is an important feature of modern stochastic geometry. Early progress in

fractal geometry often referred to sets with obvious selfsimilarity, like the _xed

pointsofiteratedfunctionsystems.

17. What is Multitexturing?

Multitexturing is the use of more than one texture at a time on a polygon. For

instance, a light map texture may be used to light a surface as an alternative torecalculating that lighting every time the surface is rendered.

18.What is turbulence.

Turbulence is a noise generating method where several noise components

are mixed and they fluctates slowly as we move slightly through the space.The

more rapidly varying componts are given smaller strengths.

Define Ray class.

Class Ray

{

public:

Point3 start;

vector3 dir;

void setstart(point3 &p){start.x=p.x;...}

void setDir(Vector &v){dir.x=v.x;...}

}
http://en.wikipedia.org/wiki/Lightmaphttp://en.wikipedia.org/wiki/Lightmaphttp://en.wikipedia.org/wiki/Lightmap


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What do you meant by self similar.

Self similarity means that two curves appear the same at any scale.No matter

how much one enlarges a picture of the curve.

cg2401 2marks for units

Documents

point x

line clipping

x tx y

point clipping

computer graphics system

xxc yyc

x direction

shearing transformation