COMPUTER GRAPHICS EXAM
QUESTIONS AND ANSWERS
what are world coordinate system - ANSWER: the main frame in the computer
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graphics in which all others are related to it
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The primary frame is the world coordinate system (WCS), also known as the
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universe or global or sometimes model coordinate system. This is the base
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reference system for the overall model (generally in 3D), to which all other model
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coordinates relate. HJ
what are the object coordinate system - ANSWER: When each object is created in a
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modelling program, a point must be picked to be
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the origin of that particular object, and the orientation of the object to a set of model
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axes
the most related coordinate system to word coordinate system
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define viewing transformation and projection transformation - ANSWER: The viewing
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transformation is the operation that maps a perspective view of an object in world
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coordinates into a physical device's display space
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Projection. HJ
Projection in computer graphics means the transformation of a three-dimensional (3D)
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area into a two-dimensional (2D) area. The plane in the area into which we
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transform (project) objects is called the 'Table'.
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projection transformation have two main types which are - ANSWER: parallel
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projection
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perspectve projection HJ
which type of projection are suitable for the following - ANSWER: scale architectural
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diagram
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we use the parallel projection
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but in realistic rendering of indoor scene we use the perspective projection
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what method used in clipping in computer graphics - ANSWER: cohenen surtherland
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method are used
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what does cohonen sutherland method depend on? - ANSWER: inside outside
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window code
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inwhich the code that not have the 0000 will be not accpeted and which have the
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0000 will be accepted
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, coheone sutherland main points - ANSWER: 1-'inside-outside window codes'. To
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determine whether endpoints are inside or outside a window
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2-As you proceed around the window, nine regions are created - the eight outside
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regions and the one inside region
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3-. Each of the nine regions associated
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with the window is assigned a 4-bit code to identify the region
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4-Each bit in the code is set to either a 1(true) or a 0(false):
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rules in the Cohen-Sutherland line-clipping algorithm - ANSWER: First bit set 1: point
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lies to the left of the window, x < xmin
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Second bit set 1: point lies to the right of the window, x > xmax
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Third bit set 1: point lies below (bottom) of the window, y < ymin
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Fourth bit set 1: point lies above (top) of the window, y > ymax
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cohen sutherland and logical or - ANSWER: The logical OR of the endpoint codes
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determines if the line is completely inside the
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window. If the logical OR is zero, the line can be trivially accepted. For example, if
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the endpoint codes are 0000 and 0000, the logical OR is 0000 - the line can be
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
trivially accepted. If the endpoint codes are 0000 and 0110, the logical OR is 0110
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and the line cannot be trivially accepted.
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what are the underlying concept of painter algorithm for hidden surface ? - ANSWER:
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It relies on the observation that if you paint on a surface, you paint over anything
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that had previously been there, thus hiding it; namely, paint from furthest to nearest
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polygons.
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sort the list of polygons by distance from viewpoint (furthest away at start of list)
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repeat the following for all polygons in the ordered list:
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draw projected polygon
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what are the situation which is not easily handled by the painters algorithm -
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ANSWER: not so good for more complex surface topologies such as certain
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overlapping polygons or the presence of holes).
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types of filling in computer graphics - ANSWER: recursive filling
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ordered filling HJ
scaline filling HJ
what are the difference between the recurise filling and the scaline filling - ANSWER:
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A pixel lying within the region to be filled is taken
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as a seed and set to record the chosen colour. The seed's nearest neighbours are
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
found and, with each in turn, this procedure is carried out recursively. The process
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
continues until the boundary is reached. HJ HJ HJ HJ HJ
The polygon is filled by stroking across each row and colouring any pixels on that
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row if they lie within the polygon:
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QUESTIONS AND ANSWERS
what are world coordinate system - ANSWER: the main frame in the computer
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
graphics in which all others are related to it
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
The primary frame is the world coordinate system (WCS), also known as the
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
universe or global or sometimes model coordinate system. This is the base
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
reference system for the overall model (generally in 3D), to which all other model
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
coordinates relate. HJ
what are the object coordinate system - ANSWER: When each object is created in a
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
modelling program, a point must be picked to be
HJ HJ HJ HJ HJ HJ HJ HJ HJ
the origin of that particular object, and the orientation of the object to a set of model
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
axes
the most related coordinate system to word coordinate system
HJ HJ HJ HJ HJ HJ HJ HJ
define viewing transformation and projection transformation - ANSWER: The viewing
HJ HJ HJ HJ HJ HJ HJ HJ HJ
transformation is the operation that maps a perspective view of an object in world
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
coordinates into a physical device's display space
HJ HJ HJ HJ HJ HJ HJ
Projection. HJ
Projection in computer graphics means the transformation of a three-dimensional (3D)
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
area into a two-dimensional (2D) area. The plane in the area into which we
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
transform (project) objects is called the 'Table'.
HJ HJ HJ HJ HJ HJ HJ
projection transformation have two main types which are - ANSWER: parallel
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
projection
HJ
perspectve projection HJ
which type of projection are suitable for the following - ANSWER: scale architectural
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
diagram
HJ HJ
we use the parallel projection
HJ HJ HJ HJ
but in realistic rendering of indoor scene we use the perspective projection
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
what method used in clipping in computer graphics - ANSWER: cohenen surtherland
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
method are used
HJ HJ HJ
what does cohonen sutherland method depend on? - ANSWER: inside outside
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
window code
HJ HJ HJ
inwhich the code that not have the 0000 will be not accpeted and which have the
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
0000 will be accepted
HJ HJ HJ HJ
, coheone sutherland main points - ANSWER: 1-'inside-outside window codes'. To
HJ HJ HJ HJ HJ HJ HJ HJ HJ
determine whether endpoints are inside or outside a window
HJ HJ HJ HJ HJ HJ HJ HJ HJ
2-As you proceed around the window, nine regions are created - the eight outside
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
regions and the one inside region
HJ HJ HJ HJ HJ HJ
3-. Each of the nine regions associated
HJ HJ HJ HJ HJ HJ
with the window is assigned a 4-bit code to identify the region
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
4-Each bit in the code is set to either a 1(true) or a 0(false):
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
rules in the Cohen-Sutherland line-clipping algorithm - ANSWER: First bit set 1: point
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
lies to the left of the window, x < xmin
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
Second bit set 1: point lies to the right of the window, x > xmax
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
Third bit set 1: point lies below (bottom) of the window, y < ymin
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
Fourth bit set 1: point lies above (top) of the window, y > ymax
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
cohen sutherland and logical or - ANSWER: The logical OR of the endpoint codes
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
determines if the line is completely inside the
HJ HJ HJ HJ HJ HJ HJ HJ
window. If the logical OR is zero, the line can be trivially accepted. For example, if
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
the endpoint codes are 0000 and 0000, the logical OR is 0000 - the line can be
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
trivially accepted. If the endpoint codes are 0000 and 0110, the logical OR is 0110
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
and the line cannot be trivially accepted.
HJ HJ HJ HJ HJ HJ
what are the underlying concept of painter algorithm for hidden surface ? - ANSWER:
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
It relies on the observation that if you paint on a surface, you paint over anything
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
that had previously been there, thus hiding it; namely, paint from furthest to nearest
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
polygons.
HJ
sort the list of polygons by distance from viewpoint (furthest away at start of list)
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
repeat the following for all polygons in the ordered list:
HJ HJ HJ HJ HJ HJ HJ HJ HJ
draw projected polygon
HJ HJ
what are the situation which is not easily handled by the painters algorithm -
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
ANSWER: not so good for more complex surface topologies such as certain
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
overlapping polygons or the presence of holes).
HJ HJ HJ HJ HJ HJ HJ
types of filling in computer graphics - ANSWER: recursive filling
HJ HJ HJ HJ HJ HJ HJ HJ HJ
ordered filling HJ
scaline filling HJ
what are the difference between the recurise filling and the scaline filling - ANSWER:
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
A pixel lying within the region to be filled is taken
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
as a seed and set to record the chosen colour. The seed's nearest neighbours are
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
found and, with each in turn, this procedure is carried out recursively. The process
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
continues until the boundary is reached. HJ HJ HJ HJ HJ
The polygon is filled by stroking across each row and colouring any pixels on that
HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ HJ
row if they lie within the polygon:
HJ HJ HJ HJ HJ HJ
