14. Define Affine transformation?

A coordinate transformation of the form

X= a

xxx + axyy + bx , y ’ ayxx + ayy y +by

is called a two-dimensional affine transformation. Each of the transformed

coordinates x ‘ and y ‘ is a linear function of the original coordinates x and y , and

parameters aij and bk are constants determined by the transformation type.

15. Distinguish between bitBlt and pixBlt?

Raster functions that manipulate rectangular pixel arrays are generally referred to

as raster ops. Moving a block of pixels from one location to another is also called a block

transfer of pixel values. On a bilevel system, this operation is called a bitBlt (bit-block

transfer), on multilevel system t is called pixBlt.

16. List out the various Text clipping?

All-or-none string clipping – if all of the string is inside a clip window, keep it

otherwise discards.

All-or-none character clipping – discard only those characters that are not

completely inside the window. Any character that either overlaps or is outside a

window boundary is clipped.

Individual characters – if an individual character overlaps a clip window

boundary, clip off the parts of the character that are outside the window.

UNIT – IV

1. What are the various representation schemes used in three dimensional objects?

Boundary representation (B-res) – describe the 3 dimensional object as a set of

surfaces that separate the object interior from the environment.

Space- portioning representation – describe interior properties, by partitioning the

spatial region containing an object into a set of small, no overlapping, contiguous

solids.

2. What is Polygon mesh?

Polygon mesh is a method to represent the polygon, when the object surfaces are

tiled, it is more convenient to specify the surface facets with a mesh function. The various

meshes are

Triangle strip – (n-2) connected triangles

Quadrilateral mesh – generates (n-1)(m-1) Quadrilateral

3. What is Bezier Basis Function?

Bezier Basis functions are a set of polynomials, which can be used instead of the

primitive polynomial basis, and have some useful properties for interactive curve design.

4. What is surface patch?

A single surface element can be defined as the surface traced out as two

parameters (u, v) take all possible values between 0 and 1 in a two-parameter

representation. Such a single surface element is known as a surface patch.

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5. Write short notes on rendering bi-cubic surface patches of constant u and v method?

The simple way is to draw the iso-parmetric lines of the surface. Discrete

approximations to curves on the surface are produced by holding one parameter constant

and allowing the other to vary at discrete intervals over its whole range. This produce

curves of constant u and constant v.

6. What are the advantages of rendering polygons by scan line method?

i. The max and min values of the scan were easily found.

ii. The intersection of scan lines with edges is easily calculated by a simple

incremental method.

iii. The depth of the polygon at each pixel is easily calculated by an

incremental method.

7. What are the advantages of rendering by patch splitting?

i. It is fast- especially on workstations with a hardware polygon-rendering

pipeline.

ii. It’s speed can be varied by altering the depth of sub-division.

8. Define B-Spline curve?

A B-Spline curve is a set of piecewise(usually cubic) polynomial segments that

pass close to a set of control points. However the curve does not pass through these

control points, it only passes close to them.

9. What is a spline?

To produce a smooth curve through a designed set of points, a flexible strip called

spline is used. Such a spline curve can be mathematically described with a piecewise

cubic polynomial function whose first and second derivatives are continuous across

various curve section.

10. What is the use of control points?

Spline curve can be specified by giving a set of coordinate positions called control

points, which indicates the general shape of the curve, can specify spline curve.

11. What are the different ways of specifying spline curve?

• Using a set of boundary conditions that are imposed on the spline.

• Using the state matrix that characteristics the spline

• Using a set of blending functions that calculate the positions along the

curve path by specifying combination of geometric constraints on the

curve

12. What are the important properties of Bezier Curve?

• It needs only four control points

• It always passes through the first and last control points

• The curve lies entirely within the convex half formed by four control

points.

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13. Differentiate between interpolation spline and approximation spline?

When the spline curve passes through all the control points then it is called

interpolate. When the curve is not passing through all the control points then that curve is

called approximation spline.

14. What do you mean by parabolic splines?

For parabolic splines a parabola is fitted through the first three points p1,p2,p3 of

the data array of kot points. Then a second parabolic arc is found to fit the sequence of

points p2, p3, p4. This continues in this way until a parabolic arc is found to fit through

points pn-2, pn-1 and pn. The final plotted curve is a meshing together of all these

parabolic arcs.

15. What is cubic spline?

Cubic splines are a straight forward extension of the concepts underlying

parabolic spline. The total curve in this case is a sequence of arcs of cubic rather than

parabolic curves

Each cubic satisfies :ax3 + bx 2+ cx + d

16. What is a Blobby object?

Some objects do not maintain a fixed shape, but change their surface

characteristics in certain motions or when in proximity to other objects. That is known as

blobby objects. Example – molecular structures, water droplets.

17. Define Octrees?

Hierarchical tree structures called octrees, are used to represent solid objects in

some graphics systems. Medical imaging and other applications that require displays of

object cross sections commonly use octree representation.

18. Define 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.

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

• Modeling Transformation

• Viewing Transformation

• Projection Transformation

• Workstation Transformation

20. What do you mean by view plane?

A view plane is nothing but the film plane in camera which is positioned

and oriented for a particular shot of the scene.

21. What is view-plane normal vector?

This normal vector is the direction perpendicular to the view plane and it

is called as [DXN DYN DZN]

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22. What is view distance?

The view plane normal vector is a directed line segment from the view

plane to the view reference point. The length of this directed line segment is referred

to as view distance

23. Define projection?

The process of converting the description of objects from world

coordinates to viewing coordinates is known as projection

24. 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.

25. 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.

26. 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.

27. What is the use of Projection reference point?

In Perspective projection, the object positions are transformed to the view

plane along these converged projection line and the projected view of an object is

determined by calculating the intersection of the converged projection lines with the

view plane.

28. What are the different types of parallel projections?

The parallel projections are basically categorized into two types,

depending on the relation between the direction of projection and the normal to the

view plane. They are orthographic parallel projection and oblique projection.

29. What is orthographic parallel projection?

When the direction of the projection is normal (perpendicular) to the view

plane then the projection is known as orthographic parallel projection

30. What is orthographic oblique projection?

When the direction of the projection is not normal (not perpendicular) to

the view plane then the projection is known as oblique projection.

31. What is an axonometric orthographic projection?

The orthographic projection can display more than one face of an object.

Such an orthographic projection is called axonometric orthographic projection.

32. What is cavalier projection?

The cavalier projection is one type of oblique projection, in which the

direction of projection makes a 45-degree angle with the view plane.

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33. What is cabinet projection?

The cabinet projection is one type of oblique projection, in which the

direction of projection makes a n angle of arctan (2)=63.4- with the view plane.

34. What is vanishing point?

The perspective projections of any set of parallel lines that are not parallel

to the projection plane converge to appoint known as vanishing point.

35. What do you mean by principle vanishing point.

The vanishing point of any set of lines that are parallel to one of the three

principle axes of an object is referred to as a principle vanishing point or axis

vanishing point.

36. What is view reference point?

The view reference point is the center of the viewing coordinate system. It

is often chosen to be close to or on the surface of the some object in the scene.

UNIT – V

1. 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.

2. What is tweening?

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

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

3. Define frame?

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

frame.

4. 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

5. 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.

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

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

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7. What are the different tricks used in computer graphics animation?

a. Color look Up Table manipulation

b. Bit plane manipulation

c. Use of UDCS

d. Special drawing modes

e. Sprites

f. Bit blitting

8. What is color look up table?

In color display unit it is necessary to read 44-bit for each pixel from

buffer. This very time consuming process. To avoid this video controller uses look up

table to store many entries of pixel vales in RGB format. This look up table is

commonly known as color look up table.

9. What is solid modeling?

The construction of 3 dimensional objects for graphics display is often

referred to as solid modeling.

10. 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.

11. 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.

12. What is the UDC technique?

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

which is used in early microcomputer system.

13. What is the use of hidden line removing algorithm?

The hidden line removal algorithm determines the lines, edges, surfaces or

volumes that are visible or invisible to an observer located at a specific point in space.

14. 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.

15. How realistic pictures are created in computer graphics?

To create a realistic picture, it must be process the scene or picture through

viewing-coordinate transformations and projection that transform three-dimensional

viewing coordinates onto two-dimensional device coordinates.

16. What is Fractals?

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

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17. What is a Fractal Dimension?

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

18. What is random fractal?

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

defects at all scale.

19. What is geometric fractal?

A geometric fractal is a fractal that repeats self-similar patterns over all

scales.

20. 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.

21. 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.

22. What is graftals?

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

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

23. 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.

24. Give some examples for computer graphics standards?

i. CORE – The Core graphics standard

j. GKS — The Graphics Kernel system

k. PHIGS – The Programmers Hierarchical Interactive Graphics System.

l. GSX – The Graphics system extension

m. NAPLPS – The North American presentation level protocol syntax.

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