computer graphics exam questions and answers latest
2022 Graded A+
what are world coordinate system
the main frame in the computer graphics in which all others are related to it
The primary frame is the world coordinate system (WCS), also known as the
universe or global or sometimes model coordinate system. This is the base
reference system for the overall model (generally in 3D), to which all other model
coordinates relate.
what are the object coordinate system
When each object is created in a modelling program, a point must be picked to be
the origin of that particular object, and the orientation of the object to a set of model
axes
the most related coordinate system to word coordinate system
define viewing transformation and projection transformation
The viewing transformation is the operation that maps a perspective view of an object in
world coordinates into a physical device's display space
Projection.
Projection in computer graphics means the transformation of a three-dimensional (3D)
area into a two-dimensional (2D) area. The plane in the area into which we transform
(project) objects is called the 'Table'.
projection transformation have two main types which are
parallel projection
perspectve projection
which type of projection are suitable for the following
scale architectural diagram
we use the parallel projection
but in realistic rendering of indoor scene we use the perspective projection
what method used in clipping in computer graphics
cohenen surtherland method are used
what does cohonen sutherland method depend on?
inside outside window code
inwhich the code that not have the 0000 will be not accpeted and which have the 0000
will be accepted
coheone sutherland main points
1-'inside-outside window codes'. To determine whether endpoints are inside or outside
a window
2-As you proceed around the window, nine regions are created - the eight outside
regions and the one inside region
3-. Each of the nine regions associated
with the window is assigned a 4-bit code to identify the region
4-Each bit in the code is set to either a 1(true) or a 0(false):
rules in the Cohen-Sutherland line-clipping algorithm
, First bit set 1: point lies to the left of the window, x < xmin
Second bit set 1: point lies to the right of the window, x > xmax
Third bit set 1: point lies below (bottom) of the window, y < ymin
Fourth bit set 1: point lies above (top) of the window, y > ymax
cohen sutherland and logical or
The logical OR of the endpoint codes determines if the line is completely inside the
window. If the logical OR is zero, the line can be trivially accepted. For example, if
the endpoint codes are 0000 and 0000, the logical OR is 0000 - the line can be
trivially accepted. If the endpoint codes are 0000 and 0110, the logical OR is 0110
and the line cannot be trivially accepted.
what are the underlying concept of painter algorithm for hidden surface ?
It relies on the observation that if you paint on a surface, you paint over anything that
had previously been there, thus hiding it; namely, paint from furthest to nearest
polygons.
sort the list of polygons by distance from viewpoint (furthest away at start of list)
repeat the following for all polygons in the ordered list:
draw projected polygon
what are the situation which is not easily handled by the painters algorithm
not so good for more complex surface topologies such as certain overlapping polygons
or the presence of holes).
types of filling in computer graphics
recursive filling
ordered filling
scaline filling
what are the difference between the recurise filling and the scaline filling
A pixel lying within the region to be filled is taken
as a seed and set to record the chosen colour. The seed's nearest neighbours are
found and, with each in turn, this procedure is carried out recursively. The process
continues until the boundary is reached.
The polygon is filled by stroking across each row and colouring any pixels on that
row if they lie within the polygon:
what are the shader variable
uniform
have a single value passed per object or
render. They are set by the CPU program and do not change until the CPU program
starts a new shader. They can be read in any shader but not written to. Examples
include light positions and transform matrices.
attribute variable in shader programmin
attribute: These variables have a different value for each vertex. These are
sent from the CPU to the shader as part of the vertex data (typically in an array).
They can be read in a vertex shader but not written to. Examples include vertex
position and normal
varying variable in shader programming
varying: are values that are passed from the vertex shader to the fragment
shader. The vertex shader computes their values for each vertex and the
rasteriser interpolates them to get a value for each fragment, which is passed to
2022 Graded A+
what are world coordinate system
the main frame in the computer graphics in which all others are related to it
The primary frame is the world coordinate system (WCS), also known as the
universe or global or sometimes model coordinate system. This is the base
reference system for the overall model (generally in 3D), to which all other model
coordinates relate.
what are the object coordinate system
When each object is created in a modelling program, a point must be picked to be
the origin of that particular object, and the orientation of the object to a set of model
axes
the most related coordinate system to word coordinate system
define viewing transformation and projection transformation
The viewing transformation is the operation that maps a perspective view of an object in
world coordinates into a physical device's display space
Projection.
Projection in computer graphics means the transformation of a three-dimensional (3D)
area into a two-dimensional (2D) area. The plane in the area into which we transform
(project) objects is called the 'Table'.
projection transformation have two main types which are
parallel projection
perspectve projection
which type of projection are suitable for the following
scale architectural diagram
we use the parallel projection
but in realistic rendering of indoor scene we use the perspective projection
what method used in clipping in computer graphics
cohenen surtherland method are used
what does cohonen sutherland method depend on?
inside outside window code
inwhich the code that not have the 0000 will be not accpeted and which have the 0000
will be accepted
coheone sutherland main points
1-'inside-outside window codes'. To determine whether endpoints are inside or outside
a window
2-As you proceed around the window, nine regions are created - the eight outside
regions and the one inside region
3-. Each of the nine regions associated
with the window is assigned a 4-bit code to identify the region
4-Each bit in the code is set to either a 1(true) or a 0(false):
rules in the Cohen-Sutherland line-clipping algorithm
, First bit set 1: point lies to the left of the window, x < xmin
Second bit set 1: point lies to the right of the window, x > xmax
Third bit set 1: point lies below (bottom) of the window, y < ymin
Fourth bit set 1: point lies above (top) of the window, y > ymax
cohen sutherland and logical or
The logical OR of the endpoint codes determines if the line is completely inside the
window. If the logical OR is zero, the line can be trivially accepted. For example, if
the endpoint codes are 0000 and 0000, the logical OR is 0000 - the line can be
trivially accepted. If the endpoint codes are 0000 and 0110, the logical OR is 0110
and the line cannot be trivially accepted.
what are the underlying concept of painter algorithm for hidden surface ?
It relies on the observation that if you paint on a surface, you paint over anything that
had previously been there, thus hiding it; namely, paint from furthest to nearest
polygons.
sort the list of polygons by distance from viewpoint (furthest away at start of list)
repeat the following for all polygons in the ordered list:
draw projected polygon
what are the situation which is not easily handled by the painters algorithm
not so good for more complex surface topologies such as certain overlapping polygons
or the presence of holes).
types of filling in computer graphics
recursive filling
ordered filling
scaline filling
what are the difference between the recurise filling and the scaline filling
A pixel lying within the region to be filled is taken
as a seed and set to record the chosen colour. The seed's nearest neighbours are
found and, with each in turn, this procedure is carried out recursively. The process
continues until the boundary is reached.
The polygon is filled by stroking across each row and colouring any pixels on that
row if they lie within the polygon:
what are the shader variable
uniform
have a single value passed per object or
render. They are set by the CPU program and do not change until the CPU program
starts a new shader. They can be read in any shader but not written to. Examples
include light positions and transform matrices.
attribute variable in shader programmin
attribute: These variables have a different value for each vertex. These are
sent from the CPU to the shader as part of the vertex data (typically in an array).
They can be read in a vertex shader but not written to. Examples include vertex
position and normal
varying variable in shader programming
varying: are values that are passed from the vertex shader to the fragment
shader. The vertex shader computes their values for each vertex and the
rasteriser interpolates them to get a value for each fragment, which is passed to
