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शुक्रवार, 8 मई 2020

Computer graphics Sort Question Answer BCA Unit IV
मई 08, 2020

Computer graphics Sort Question Answer BCA 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?
A 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
Σ Triangle strip – (n-2) connected triangles
Σ Quadrilateral mesh – generates (n-1)(m-1) Quadrilateral
3. Define the 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.
4. 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 the piecewise cubic polynomial function whose first and second derivatives are continuous across various curve section.
5. 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.
6. What are the different ways of specifying a spline curve?
Σ Using a set of boundary conditions that are imposed on the spline.
Σ Using the state matrix that characteristics the spline
Σ Using a set of blending functions that calculate the positions along the curve path by
specifying a combination of geometric constraints on the curve.
7. 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.
8. 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.
9. 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.
10. 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.
11. 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. The process of converting the description of objects from world coordinates to viewing coordinates is known as projection.
12. What do you mean by view plane?
A view plane is nothing but the film plane in the camera which is positioned and oriented for a particular shot of the scene.
13. What is view-plane normal vector?
This a normal vector is the direction perpendicular to the view plane.

14. What is the various representation schemes used in three-dimensional objects?
Boundary representation (B-res) – describe the 3 dimensional objects as a set of surfaces that separate the object interior from the environment.
Space- portioning representation – describe the interior properties, by partitioning the spatial region containing an object into a set of small, no overlapping, contiguous solids.

15. What is Polygon mesh?

A 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
16. What is a 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.
17. 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.

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

i. It is fast- especially on workstations with a hardware polygon-rendering pipeline.
ii. Its speed can be varied by altering the depth of sub-division.
19. Define the 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.
20. 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.

21. 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 a spline curve.
22. What are the different ways of specifying a spline curve?

• Using a set of boundary conditions that are imposed on the spline.
• Using the state matrix that characteristics of 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.
23. 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.
24. 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.
25. 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.
26. What is the 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
27. 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.
28. 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.
29. What are the steps involved in 3D transformation?

- Modeling Transformation
-Viewing Transformation
-Projection Transformation
-Workstation Transformation

30. What do you mean by the view plane?

A view plane is nothing but the film plane in the camera which is positioned and oriented for a particular shot of the scene.
31. 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]
32. What is view distance?

The view a 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


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बुधवार, 6 मई 2020

मई 06, 2020

BCA 4th SEm -- Spatial Partitioning Representations

  • UNIT-I 
The Advantages of Interactive Graphics
Representative Uses of Computer Graphics 
Classification of Application Development of Hardware and software for computer Graphics
Overview, Scan:
Converting Lines
Scan Converting Circles
Scan Converting Ellipses








  • UNIT-II 
    • Hardcopy Technologies
    Display Technologies
    Raster-Scan Display System
    Video Controller
    Random-Scan Display processor
    Input Devices for Operator Interaction
    Image Scanners
    Working exposure on graphics tools like Dream Weaver, 3D Effects etc
    Clipping
    Southland- Cohen Algorithm
    Cyrus-Beck Algorithm
    Midpoint Subdivision Algorithm









  • UNIT-III 
    • Geometrical Transformation
    2D Transformation
    Homogeneous Coordinates and Matrix Representation of 2DTransformations 
    composition of 2D Transformations
    The Window-to-Viewport
    Transformations







  • UNIT-V                           

    • Multimedia Definition
    CD-ROM and the multimedia highway
    Computer Animation
    (Design, types of animation, using different functions)







  • UNIT-VI  

    • Uses of Multimedia
    Introduction to making multimedia –
    The stage of Project
    hardware & software requirements to make good multimedia skills
    Training opportunities in Multimedia Motivation for Multimedia usage

    Spatial Partitioning Representations

     it is used to describe interior properties, by partitioning the spatial region, containing an object into a set of small, non-overlapping, contiguous solids. e.g. 3D object as Octree representation. 


    a solid is decomposed into a collection of adjoining, nonintersecting solids using spatial partitioning representations,. A quadtree is a representation format used to encode images. The fundamental idea behind the quadtree is that any image can be split into four quadrants. Each quadrant may again be split into four sub-quadrants, etc. In the quadtree, a parent node represents the image, while four child nodes, in a predetermined order, represent the four quadrants.

    The following are different spatial partitioning techniques:

    1.Cell Decomposition
    2.Spatial Occupancy Enumeration
    3.Quadtrees and Octrees
    4.Binary space partitioning Trees








     

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    मई 06, 2020

    BCA 4th Sem - Boundary Representations

    • UNIT-I 
    ~The Advantages of Interactive Graphics
    ~Representative Uses of Computer Graphics 
    ~Classification of Application Development of Hardware and software for computer Graphics
    ~Overview, Scan:
    ~Converting Lines
    ~Scan Converting Circles
    ~Scan Converting Ellipses






  • UNIT-II 
    • ~Hardcopy Technologies
    ~Display Technologies
    ~Raster-Scan Display System
    ~Video Controller
    ~Random-Scan Display processor
    ~Input Devices for Operator Interaction
    ~Image Scanners
    ~Working exposure on graphics tools like Dream Weaver, 3D Effects etc
    ~Clipping
    ~Southland- Cohen Algorithm
    ~Cyrus-Beck Algorithm
    ~Midpoint Subdivision Algorithm







  • UNIT-III 
    • ~Geometrical Transformation
    ~2D Transformation
    ~Homogeneous Coordinates and Matrix Representation of 2DTransformations 
    ~composition of 2D Transformations
    ~The Window-to-Viewport
    Transformations




  • UNIT-V                           

    • ~Multimedia Definition
    ~CD-ROM and the multimedia highway
    ~Computer Animation
    (Design, types of animation, using different functions)





  • UNIT-VI  

    • ~Uses of Multimedia
    ~Introduction to making multimedia –
    ~The stage of Project
    ~hardware & software requirements to make good multimedia skills
    ~Training opportunities in Multimedia Motivation for Multimedia usage

    Boundary Representations

    Boundary Representation, or B-rep for short, can be considered as an extension to the wireframe model. The merit of a B-rep is that a solid is bounded by its surface and has its interior and exterior. 

     The surface of solid consists of a set of well-organized faces, each of which is a piece of some surface (.e.g., a surface patch). Faces may share vertices and edges that are curve segments. Therefore, a B-rep is an extension of the wireframe model by adding face information to the latter.

     There are two types of information in a B-rep: 

    1. topological
    2.  geometric.


      Topological information provides the relationships among vertices, edges, and faces similar to that used in a wireframe model. In addition to connectivity, topological information also includes the orientation of edges and faces. 

     Geometric information is usually equations of the edges and faces.

    • The geometry of a vertex is just its position in space as given by its (x,y,z) coordinates.
    • Edges may be straight lines, circular arcs, etc..
    • A face is represented by some description of its surface (algebraic or parametric forms used).
      Boundary Representation (B-rep)

    Validity Check Using Euler-Poincare Example
    Given the boundary representation solid shown, verify the Euler-Poincare relationship.
    The Euler equation provides an invariant relationship between the vertices, edges, and
    surfaces of a simple polyhedral object. The Euler-Poincare equation expands this relation to
    include objects with holes, passages, etc.

    For the object at right:

    Vertices = 24
    Edges = 36
    Faces = 14

    Make sure to look at ALL the faces that bound the volume, then find the bounding edges for
    those faces and finally the vertices associated with the edges. Check your count twice. Don’t forget that the rounds require their own surface definitions.

    Genus = 1 (one through passage)
    Shell = 1 (no internal void)
    (Hole) Loops = 2
    Solving the Euler-Poincare equation:

    V – E + F – L       = 2 (S – G)
    24 – 36 + 14 – 2 = 2 (1 – 1)
                                0 = 0


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