# Sample Paper For Computer Graphics

Sample Paper For Computer Graphics given with their solution which is very important for the student of Computer Science & Engineering branch that is important for the semester point of view.Before going on Sample Paper For Computer Graphics we will give brief introduction of Computer Graphics.

**Introduction of Computer graphics**

Computer graphics is the pictorial representation of information using a computer program. It is a set of models, methods and techniques to transform data into images that are displayed in a graphics device.By using the Computer Graphics Technology we can enhance the quality of a picture by using computer technology,Enhancing quality mean we can modify image from poor quality to high tech image.

**Q.1 Answer the following questions:**

**(a) What is Computer Graphics?**

**Ans:-** The representation and manipulation of image data by a computer with the help from specialized software and hardware is called computer graphics.

**(b) What do you mean by GUI?**

**Ans:-** GUI stands for Graphical User Interface. A major component of a GUI is a window manager that allows a user to display multiple window areas. To make a particular window active we simply click in that window using an interactive pointing device.

**(c) What are the applications of computer graphics?**

**Ans:-** 1. Computer Aided Design

2. Graphical User Interface

3. Entertainment

4. simulation and training

5. Education and Presentation

6. Computer Generated Art

7. Scientific Visualization

8. Image Processing

9. Virtual reality

10. Cartography

**(d) Define refresh buffer?**

**Ans:-** The memory area where in picture definition is stored is called Refresh buffer.

**(e) What are the disadvantages of DDA algorithm?**

**Ans:- ** 1. Round off error in successive additions of the floating point increment can cause the calculated pixel positions to drift away from the true line path for long line segments.

2. Rounding operations and floating point arithmetic in procedure are still time consuming.

**(f) Define scaling.**

**Ans:-** A scaling transformation alters the size of an object. This operation can be carried out for polygons by multiplying the coordinate values(x,y) of each vertex by scaling factors sx and sy to produce the transformed coordinates(x^{1}, y^{1}).x^{1}=x.sx, y^{1}=y.sy.

**(g) Distinguish between window port and view port.**

**Ans:-** A portion of a picture that is to be displayed by a window is known as window port. The display area of the part selected or the form in which the selected part is viewed is known as view port.

**(h) Define ellipse.**

**Ans:-** An ellipse can use the same parameters xc, yc, r as a circle, in addition to the eccentricity e. The equation of an ellipse is (x-xc)^{2}/a^{2}+(y-yc)^{2}/b^{2}=1

**(i) ****What are different techniques for 3D transformation?**

**Ans:- ** Different techniques for 3D transformation involves,

(i) 3D Rotation

(ii) 3D Translation

(iii) 3D Scaling

**(j) What is A-Buffer method?**

**Ans:-** A-Buffer method represents an area averaged, accumulation buffer method. It expands the depth buffer so that each position in the buffer can be reference a list of surfaces.

**2. Write down the algorithm for Bresenham’s Line Drawing.**

**Ans:-** **Step 1:-** Input the two end points of the line and store the left end point in (x_{0, }y_{0}).

**Step 2:-** Load (x_{0, }y_{0}) into frame buffer.

**Step 3:-** Calculate the constants x^{1 }, 2y^{1 }, 2x^{1 }and obtain the starting value for the decision parameter as d_{0}=2y^{1}– x^{1}.

**Step 4:-** At each x_{k }along the line starting at k=o, perform the following operation

If d_{k }< 0 then

Next point is to plot (x_{k+1 }, y_{k})

d_{k+1 }= d_{k }+ 2y^{1 }

else

The next point is to plot (x_{k+1 }, y_{k+1})

d_{k+1 }= d_{k }+ 2y^{1 }-2x^{1 }

**Step 5:-** Repeat Step 4 x^{1 }times.

**3. Distinguish between Raster and Random Scan display.**

**Ans:-** Raster scan display draws the image by scanning one row at a time. They generally have resolution limited to pixel size. Lines are jiggered and curves are less smoother. They are more suited to geometric area drawing applications e.g, monitors, Television.

Random scan display draws the image by directing the electron beam directly to the part of the screen where the image is to be drawn. They have higher resolution than raster scan system. Line plots are straight and curves are smooth. They are more suited to line drawing application e.g, CRO, pen plotter.

**4. Explain the merits and demerits of Plasma panel display.**

**Ans:-** Advantages of Plasma panel display:-

- Refreshing is not required.
- Produce a very steady image free of flicker and less bulky than a CRT.

Disadvantages of Plasma panel display:-

- Poor resolution of up to 60 dots per unit.
- It requires complex addressing and writing.
- It is costlier than CRT.

**5.What are different types of coherence?**

**Ans:-** Object Coherence:- Visibility of an object can often be decided by examining a circumscribing solid(which may be of simple form, e.g. A sphere or a polyhedron.)

**Face coherence**:- Surface properties computed for one part of a face can be applied to adjacent parts after small incremental modification.(e.g. if one part of the face is invisible to the viewer, the entire face is also available).

**Edge coherence**:- The visibility of an edge changes only when it crosses another edge, so if one segment of an non intersecting edge is visible, the entire edge is also visible.

**Scan line coherence**:- Line of surface segments visible in one scan line are also likely to be visible in adjacent scale lines. Consequently, the image of a scan line is similar to the image of adjacent scan lines.

**6. What are the properties of a Bezier curve?**

**Ans:-** A Bezier curve is determined by a defining polygon. Bezier curves have a number of properties that make them highly useful and convenient for curve and surface design.

**Properties of Bezier Curve:-**

- The basic functions are real.
- Bezier curve always passes through the first and last control points i.e., curve has same end points as the guiding polygon.
- The degree of the polynomial defining the curve segment is one less than the number of defining the curve segment is one less than the number of defining polygon point. Therefore , for four control points, the degree of the polynomial is three, i.e., cubic polynomial.
- The curve generally follows the shape of defining polygon.
- The direction of the tangent vector at the end points is the same as that of the vector determined by first and last segments.
- The curve lies entirely within the convex hull formed by four control points.
- The convex hull properties for a Bezier curve ensures that the polynomial smoothly follows the control points.
- The curve exhibits the variation diminishing property. This means that the curve does not oscillate about any straight line more often that the defining polygon.
- The curve is invariant under an affine transformation.

**7. Explain the difference between image processing and computer graphics.**

**Ans:**– Image processing:-

Image processing applies techniques to modify or interpret existing pictures.

To apply image processing methods, the image must be digitalized first.

Medical applications also make extensive use of image processing techniques for picture enhancement, simulations of operations, etc.

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A good suggestion paper of the subject “Computer Graphics”.