NOV/DEC
2011
1.Write
down the line attributes?
Basic attributes of a
straight line segment are its type, its width, and its color. In some graphics
packages, lines can also be displayed using selected pen or brush options.
·
Line Type
·
Line Width
·
Pen and Brush Options
·
Line Color
2.Differentiate
window and viewport?
Window:
·
A world coordinate area selected for
display is called a window.
·
The window defines what is to be viewed
View
port:
·
An area on a display device to which a
window is mapped is called a view port.
·
The view port defines where it is to be
displayed.
3.What are spline curves?
A Spline is a flexible strip used to
produce a smooth curve through a designated set of points. The Spline curve refers to any sections curve
formed with polynomial sections satisfying specified continuity conditions at
the boundary of the pieces.
4.Define quadratic surfaces
·
The quadric surfaces are described with
second degree equations (quadratics).
·
They include spheres, ellipsoids, tori,
parabolids, and hyperboloids.
5.What is animation?
·
Computer animation refers to any time
sequence of visual changes in a scene.
·
Computer animations can also be
generated by changing camera parameters such as position, orientation and focal
length.
·
Applications of computer-generated
animation are entertainment, advertising, training and education.
·
Example : Advertising animations often
transition one object shape into another.
6.Define keyframes.
·
A key frame is detailed drawing of the
scene at a certain time in the animation sequence.
·
Within each key frame, each object is
positioned according to the time for that frame.
·
Some key frames are chosen at extreme
positions in the action; others are spaced so that the time interval between
key frames is not too much.
·
7.What do you mean by shading of
objects?
·
A shading model dictates how light is
scattered or reflected from a surface. The shading models described here
focuses on achromatic light. Achromatic lighthas brightness and no color, it is
a shade of gray so it is described by a single value its intensity.
·
A shading model uses two types of light
source to illuminate the objects in a scene :
i.
point light sources
ii.
ambient light.
8.What is texture?
·
The realism of an image is greatly
enhanced by adding surface texture to various faces of a mesh object.
·
The basic technique begins with some
texture function, texture(s,t)in texture space , which has two parameters s and
t. The function texture(s,t) produces a color or intensity value for each value
of s and t between 0(dark)and 1(light).
·
The two common sources of textures are
i.
Bitmap Texture
ii.
Procedural Textures
9.Define fractals.
·
Fractal is the term associated with
randomly generated curves and surfaces that exhibit a degree of
self-similarity.
·
These curves are used to provide
“naturalistic” shapes for representing objects such as coastlines, rugged
mountains, grass and fire
10.differentiate Mandelbrot and Julia
sets.
Mandelbrot:
·
The Mandelbrot set M is the set of all
complex numbers c that produce a finite orbit of 0.
·
If c is chosen outside of M, the
resulting orbit explodes. If c is chosen just beyond the border of M, the orbit
usually thrashes around the plane and goes to infinity.
·
If the value of c is chosen inside M,
the orbit can do a variety of things. For some c‟s
it goes immediately to a fixed point or spirals into such a point.
Julia sets:
·
The filled-in Julia set at c, Kc, is the
set of all starting points whose orbits are finite.
·
When studying Kc, one chooses a single
value for c and considers different starting points. Kc should be always symmetrical
about the origin, since the orbits of s and –s become identical after one
iteration.
·
NOV/DEC 2012
1.Write down the shere transformation
matrix.
2.Define text clipping.
·
There are several techniques that can be
used to provide text clipping in a graphics package
·
The simplest method for processing
character strings relative to a window boundary is to use the all-or-none
string-clipping strategy. If all of the string is inside a clip window, we keep
it. Otherwise, the string is discarded.
3.Differentiate oblique and orthogonal projections.
Oblique projections:
·
An oblique projection in obtained by
projecting points along parallel lines that are not perpendicular to the
projection plane.
Orthogonal projection:
An ORTHOGRAPHIC
projection is a parallel
projection in which the projectors are perpendicular to
the plane of projection
4. What are spline curves?
A Spline is a flexible strip used to
produce a smooth curve through a designated set of points. The Spline curve refers to any sections curve
formed with polynomial sections satisfying specified continuity conditions at
the boundary of the pieces.
5.State the difference between CMY and
HSV color models.
CMY color model:
·
A color model defined with the primary
colors cyan, magenta, and yellow (CMY) in useful for describing color output to
hard copy devices.
·
It is a subtractive color model (i.e.,)
cyan can be formed by adding green and blue light.
·
When white light is reflected from
cyan-colored ink, the reflected light must have no red component. i.e., red
light is absorbed or subtracted by the link.
HSV color model:
·
The HSV model uses color descriptions
that have a more interactive appeal to a user.
·
Color parameters in this model are hue
(H), saturation (S), and value (V).
·
The 3D representation of the HSV model
is derived from the RGB cube. The outline of the cube has the hexagon shape.
6. What are keyframes systems?
·
Each set of in-betweens are generated
from the specification of two keyframes.
·
For complex scenes, we can separate the
frames into individual components or objects called cells, an acronym from
cartoon animation.
7.What is a shadow?
·
Shadows make an image more realistic.
The way one object casts ashadow on another object gives important visual clues
as to how the two objects are positioned with respect to each other.
·
Shadows conveys lot of information as
such, you are getting a second look at the object from the view point of the
light source.
·
There are two methods for computing
shadows:
i.
Shadows as Texture
ii.
Creating shadows with the use of a shadow
buffer
8.Define texture.
·
The realism of an image is greatly
enhanced by adding surface texture to various faces of a mesh object.
·
The basic technique begins with some
texture function, texture(s,t)in texture space , which has two parameters s and
t. The function texture(s,t) produces a color or intensity value for each value
of s and t between 0(dark)and 1(light).
·
The two common sources of textures are
iii.
Bitmap Texture
iv.
Procedural Textures
9.List down the properties of piano
curves.
10.Write down some of the Boolean
operations on objects.
The Boolean operators: union,
intersection and difference
Union: R=C1 U C2 U C3 U C4
Intersection: L=S1∩S2
Difference: B=(S1-S2)-C.
MAY/JUNE
2012
1. What is the major difference
between symmetrical DDA and simple DDA?
The
DDA (Digital Differential Analyzer) algorithm is used to find out interpolating
points between any given two points, linearly (i.e. straight line). The DDA
method can be implemented using floating-point or integer arithmetic.
Symmetrical DDA (digital differential
analyzer) generates lines from their differential equations. It is can also be
used to generate arcs and other curves
In general, the appearance of lines generated by
the DDA depends on what value is chosen for epsilon.
(1) Symmetrical DDA: Choose epsilon = 2^n where
2^(n-1) <= max(|deltax|,|deltay|) < 2^n. This then implies that the line
length estimate is 2^n.
Problem: Generate a line from point (0,0) to (4,3)
using the symmetrical DDA.
(2) Simple DDA - Choose a line length estimate that
is equal to the max(deltax,deltay) in such a way that e(deltax) or e(deltay) is
of unit magnitude. This implies that one of the counters is simply an increment
by 1. That is, if e=1/(max(deltax,deltay)) then either e(deltax)=1 or
e(deltay)=1.
2. What is the use
of clipping?
Any
procedure that identifies those portions of a picture that are inside or
outside of a specified region of space is referred to as clipping algorithm
or clipping. The region against which an object is to be clipped is called clip
window.
Algorithm for clipping primitive types:
Point clipping
Line
clipping (Straight-line segment) A
rea
clipping
Curve
clipping
Text
clipping
3. Differentiate
parallel projection from perspective projection,
Parallel projection
It
is a method for generating a view of a solid object is to project points on the
object surface along parallel lines onto the display plane.
In parallel
projection, parallel lines in the world coordinate scene project into parallel
lines on the two dimensional display planes.
This technique is used in engineering
and architectural drawings
perspective
projection
It is a method for
generating a view of a three dimensional scene is to project points to the
display plane alone converging paths. This makes objects further from the
viewing position be displayed smaller than objects of the same size that are
nearer to the viewing position.
In
a perspective projection, parallel lines in a scene that are not parallel to
the display plane are projected into converging lines. Scenes displayed using
perspective projections appear more realistic, since this is the way that our
eyes and a camera lens form images.
4. Define
viewing.
we can view an
object from any spatial position, from the front, from above or from the back.
We could generate a view of what we
could see if we were standing in the middle of a group of objects or inside
object, such as a building.
5. What are
subtractive colors?
Subtractive
color mixing is the kind of mixing you get if you
illuminate colored filters with white light from behind, as illustrated
at left. The commonly used subtractive primary colors are cyan,
magenta and yellow, and if you overlap all three in effectively equal mixture,
all the light is subtracted giving black.
6. What do you
mean by temporal aliasing?
Aliasing can occur in signals sampled in
time, for instance digital audio, and is referred to as temporal
aliasing. Aliasing can also occur in spatially sampled signals, for
instance digital images. Aliasing in spatially
sampled signals is called spatial aliasing
7. Define
shading.
Shading
is used in drawing for depicting levels of darkness on paper by applying media
more densely or with a darker shade for darker areas, and less densely or with
a lighter shade for lighter areas.
8. What is
texture?
In 3D
graphics, the digital representation of the surface of an object, such as
color and brightness, a texture is also encoded with three-dimensional
properties, such as how transparent and reflective the object is. Once a
texture has been defined, it can be wrapped around any 3-dimensional object.
This is called texture
mapping.
9. Define
fractals.
A fractal
is a natural phenomenon or a mathematical set that exhibits a
repeating pattern that displays at every scale. If the replication is exactly
the same at every scale, it is called a self-similar pattern. Fractals can also be nearly the same at
different levels
10. What is
Julia sets?
Like
the Mandelbrot set, Julia sets are extremely complicated sets of points in the
complex plane. There is a different Julia set, denoted Jc for each value of c.
A closely related variation is the filled-in Julia set, denoted by Kc, which
is easier to define.
NOVEMBER/DECEMBER
2013.
1.List
the different types of text clipping methods available?
1. All-or-none string clipping - if
all of the string is inside a clip window,
keep it otherwise discards.
2. 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.
3. Individual characters – if an
individual character overlaps a clip
window boundary, clip off the parts
of the character that are outside the window.
2. Give the general expression of Bezier Bernstein polynomial.
The
n + 1 Bernstein basis polynomials of degree n
are defined as
where 
is a binomial coefficient
is a binomial coefficient
3.
Give the single-point perspective projection transformation matrix
when projectors are placed on the z-axis?
The
simplest perspective projection uses the origin as the center of projection,
and z = 1 as the image plane. The functional form of this transformation
is then 
; 
. We can express
this in homogeneous coordinates
as:
; . We can express
this in homogeneous coordinates
as:
4. List any four real time animation
techniques
1.
Raster
animation
2.
Keyframe
animation
3.
Rendering
