Introduction Flashcards

Question

Interactive picture construction technique

Answer 1

❖ Basic Positioning methods ❖ Constraints ❖ Grids ❖ Gravity Fields ❖ Rubber-band methods ❖ Sketching ❖ Dragging

Answer 2

❖ It is an electromechanical device, which accepts data from a computer and translates them into form understand by users. ❖ There are various types of hard copy output devices including: ❖ Printers ❖ Plotters ❖ 3-D Printers 3.1.1.1 Basic definition of terms ❖ Dot Size ❖ Addressability ❖ Inter dot distance ❖ Resolution

Answer 3

❖ Printer is the most important output device, which is used to print data on paper. ❖ Types of Printers: ❖ There are many types of printers which are classified on various criteria as shown in the figure. ❖ Impact Printers: The printers that print the characters by striking against the ribbon and onto the papers are known as Impact Printers. ❖ These Printers are of two types: ❖ Character Printers ❖ Line Printers ❖ Non-Impact Printers: The printers that print the characters without striking against the ribbon and onto the papers are called Non-Impact Printers. These printers print a complete page at a time, therefore, also known as Page Printers. ❖ Page Printers are of two types: ❖ Laser Printers ❖ Inkjet Printers

Answer 4

❖ Drum Printers ❖ Dot matrix ❖ Chain ❖ InkJet ❖ Laser ❖ Plotter

Answer 5

❖ These are line printers, which prints one line at a time. ❖ It consists of a drum. ❖ The shape of the drum is cylindrical. ❖ The drum is solid and has characters embossed on it in the form of vertical bands. ❖ The characters are in circular form. ❖ Each band consists of some characters. ❖ Each line on drum consists of 132 characters. ❖ Because there are 96 lines so total characters are (132 * 95) = 12, 672. ❖ Drum contains a number of hammers also. Computer

Answer 6

❖ Dot matrix has printed in the form of dots. ❖ A printer has a head which contains nine pins. ❖ The nine pins are arranged one below other. ❖ Each pin can be activated independently. ❖ All or only the same needles are activated at a time. ❖ When needless is not activated, and then the tip of needle stay in the head. ❖ When pin work, it comes out of the print head. ❖ In nine pin printer, pins are arranged in 5 * 7 matrixes. 3.1.1.5.1 Advantages of DOT MATRIX Printers ❖ Dot Matrix Printers prints output as dots, so it can print any shape of the character. This allows the printer to print special character, charts, graphs, etc. ❖ Dot Matrix Printers come under the category of impact printers. The printing is done when the hammer pin strikes the inked ribbon. The impressions are printed on paper. By placing multiple copies of carbon, multiple copies of output can be produced. ❖ It is suitable for printing of invoices of companies.

Answer 7

❖ Head is lying on a wheel and Pins corresponding to characters are like petals of Daisy, that's why called Daisy wheel printer. 3.1.1.6.1 Advantages ❖ More reliable than DMPs ❖ Better Quality 3.1.1.6.2 Disadvantages ❖ Slower than DMPs.

Answer 8

❖ These are called as line printers. ❖ These are used to print one line at a line. ❖ Basically, chain consists of links. ❖ Each link contains one character. ❖ Printers can follow any character set style, i.e., 48, 64 or 96 characters. ❖ Printer consists of a number of hammers also. 3.1.1.7.1 Advantages ❖ Chain or Band if damaged can be changed easily. ❖ It allows printing of different form. ❖ Different Scripts can be printed using this printer. 3.1.1.7.2 Disadvantages ❖ It cannot print charts and graphs. ❖ It cannot print characters of any shape. ❖ Chain Printers is impact printer, hammer strikes so it is noisy.

Answer 9

❖ These printers use a special link called electrostatic ink. ❖ The printer head has a special nozzle. Nozzle drops ink on paper. ❖ Head contains up to 64 nozzles. ❖ The ink dropped is deflected by the electrostatic plate. ❖ The plate is fixed outside the nozzle. ❖ The deflected ink settles on paper.

Answer 10

3.1.1.8.1 Advantages ❖ These produce high quality of output as compared to the dot matrix. ❖ A high-quality output can be produced using 64 nozzles printed. ❖ Inkjet can print characters in a variety of shapes. ❖ Inkjet can print special characters. ❖ The printer can print graphs and charts. 3.1.1.8.2 Disadvantages ❖ Inkjet Printers are slower than dot matrix printers. ❖ The cost of inkjet is more than a dot matrix printer.

Answer 11

❖ These are non-impact page printers. They use laser lights to produces the dots needed to form the characters to be printed on a page & hence the name laser printers. ❖ The output is generated in the following steps: ❖ Step1: The bits of data sent by processing unit act as triggers to turn the laser beam on & off. ❖ Step2: The output device has a drum which is cleared & is given a positive electric charge. To print a page the modulated laser beam passing from the laser scans back & forth the surface of the drum. The positive electric charge on the drum is stored on just those parts of the drum surface which are exposed to the laser beam create the difference in electric which charges on the exposed drum surface. ❖ Step3: The laser exposed parts of the drum attract an ink powder known as toner. ❖ Step4: The attracted ink powder is transferred to paper. ❖ Step5: The ink particles are permanently fixed to the paper by using either heat or pressure technique. ❖ Step6: The drum rotates back to the cleaner where a rubber blade cleans off the excess ink & prepares the drum to print the next page.

Answer 12

3.1.1 Hard Copy Output Devices ❖ It is an electromechanical device, which accepts data from a computer and translates them into form understand by users. ❖ There are various types of hard copy output devices including: ❖ Printers ❖ Plotters ❖ 3-D Printers 3.1.1.1 Basic definition of terms ❖ Dot Size ❖ Addressability ❖ Inter dot distance ❖ Resolution

Answer 13

3.1.1 Hard Copy Output Devices ❖ It is an electromechanical device, which accepts data from a computer and translates them into form understand by users. ❖ There are various types of hard copy output devices including: ❖ Printers ❖ Plotters ❖ 3-D Printers 3.1.1.1 Basic definition of terms ❖ Dot Size ❖ Addressability ❖ Inter dot distance ❖ Resolution

Answer 14

3.1.1.10 PLOTTERS ❖ Plotters are a special type of output device. It is suitable for applications like: ❖ Architectural plan of the building. ❖ CAD applications like the design of mechanical components of aircraft. Computer Graphics 15 3.1.1.10.1 Advantages ❖ It can produce high-quality output on large sheets. ❖ It is used to provide the high precision drawing. ❖ It can produce graphics of various sizes. ❖ The speed of producing output is high.

Answer 15

3.1.1.11 DRUM PLOTTER ❖ It consists of a drum. Paper on which design is made is kept on the drum. ❖ The drum can rotate in both directions. ❖ Plotters comprised of one or more pen and penholders. ❖ The holders are mounted perpendicular to drum surface. ❖ The pens are kept in the holder, which can move left to the right as well as right to the left. ❖ The graph plotting program controls the movement of pen and drum.

Answer 16

SCAN CONVERSION DEFINITION ❖ It is a process of representing graphics objects a collection of pixels. ❖ The graphics objects are continuous. ❖ The pixels used are discrete. Each pixel can have either on or off state. ❖ The circuitry of the video display device of the computer is capable of converting binary values (0, 1) into a pixel on and pixel off information. ❖ 0 is represented by pixel off. ❖ 1 is represented using pixel on. ❖ Using this ability graphics computer represent picture having discrete dots. ❖ Any model of graphics can be reproduced with a dense matrix of dots or points. ❖ Most human beings think graphics objects as points, lines, circles, ellipses. ❖ For generating graphical object, many algorithms have been developed.

Answer 17

4.1.1 ADVANTAGE OF DEVELOPING ALGORITHMS FOR SCAN CONVERSION ❖ Algorithms can generate graphics objects at a faster rate. ❖ Using algorithms memory can be used efficiently. ❖ Algorithms can develop a higher level of graphical objects.

Answer 18

4.1.2 ADVANTAGE OF DEVELOPING ALGORITHMS FOR SCAN CONVERSION ❖ Point ❖ Line ❖ Sector ❖ Arc ❖ Ellipse ❖ Rectangle ❖ Polygon ❖ Characters ❖ Filled Regions ❖ The process of converting is also called as rasterization. ❖ The algorithms implementation varies from one computer system to another computer system. ❖ Some algorithms are implemented using the software. ❖ Some are performed using hardware or firmware. ❖ Some are performed using various combinations of hardware, firmware, and software.

Answer 19

4.2.2.2 ALGORITHM FOR LINE DRAWING ❖ Direct use of line equation ❖ DDA (Digital Differential Analyzer) ❖ Bresenham's Algorithm

Answer 20

4.2.2.2 ALGORITHM FOR LINE DRAWING ❖ Direct use of line equation ❖ DDA (Digital Differential Analyzer) ❖ Bresenham's Algorithm

Answer 21

5. TWO DIMENSIONAL TRANSFORMATIONS Some visuals are transformed into some other graphics by implementing several of the principles known as transformation. There are multiple kinds of transformation, including translation, scaling, rotation, shearing, etc. Whenever this transition occurs in the 2D plane, it is defined as the 2D transformation. Transformations play a significant role in computer graphics, and reorient the visuals on display and adjust the scale or orientation. The aim of using illustrating computer devices is to offer users the ability to visualize the object from multiple angles, expand or decrease the object’s size or position, known as Transformation.

Answer 22

5. TWO DIMENSIONAL TRANSFORMATIONS Some visuals are transformed into some other graphics by implementing several of the principles known as transformation. There are multiple kinds of transformation, including translation, scaling, rotation, shearing, etc. Whenever this transition occurs in the 2D plane, it is defined as the 2D transformation. Transformations play a significant role in computer graphics, and reorient the visuals on display and adjust the scale or orientation. The aim of using illustrating computer devices is to offer users the ability to visualize the object from multiple angles, expand or decrease the object’s size or position, known as Transformation.

Answer 23

5.1 BASIC TRANSFORMATION The 2D transformation involves- 1. 2D Translation: “Translation is a method used to shift the entity on the monitor from one location to another location.” 2. 2D Rotation: "Rotation is a technique used to twist an entity from its source to a certain angle." 3. 2D Scaling: "Scaling is a form or method used in a two-dimensional plane to resize the entity." 4. 2D Reflection: "Reflection is a phase or system through which the entity can be rotated at a 180 ° angle." 5. 2D Shearing: "Shearing is a technique that is used to conduct the entity's slanting." It is often referred to as "Skewing."

Answer 24

5.1.1 TRANSLATION MATRIX ❖ A translation moves an object to a different position on the screen. You can translate a point in 2D by adding translation coordinate (tx, ty) to the original coordinate X,Y to get the new coordinate X′,Y′. From the above figure, you can write that − X’ = X + t x , Y’ = Y + t y The pair (tx , ty ) is called the translation vector or shift vector. The above equations can also be represented using the column vectors. P=[X]/[Y] P' = [X′][Y′] T = [tx][ty] We can write it as − P’ = P + T

Answer 25

5.1.3 ROTATION ❖ The Rotation of any object depends upon the two points. ❖ Rotation Point: It is also called the Pivot point. ❖ Rotation Angle: It is denoted by Theta (θ). ❖ We can rotate an object in two ways- ❖ Clockwise: An object rotates clockwise if the value of the Rotation angle is negative (-). ❖ Anti-Clockwise: An object rotates anti-clockwise if the value of t ❖ We can apply Rotation on following objects- ❖ Straight Lines ❖ Curved Lines ❖ Polygon ❖ Circle Computer Graphics 6 ❖ For Example- ❖ Rotation of a Point: If we want to Rotate a point A (P0, Q0) that has a Rotation angle (θ) with distance r from origin to A` (P1, Q1) that has a Rotation angle β . Then, we can rotate by following Rotation equation- 5.1.4 REFLECTION ❖ Reflection is the mirror image of original object. In other words, we can say that it is a rotation operation with 180°. In reflection transformation, the size of the object does not change. ❖ The following figures show reflections with respect to X and Y axes, and about the origin respectively. 5.1.5 SHEAR ❖ A transformation that slants the shape of an object is called the shear transformation. There are two shear transformations X-Shear and Y-Shear. One shifts X coordinates values and other shifts Y coordinate values. However; in both the cases only one coordinate changes its coordinates and other preserves its values. Shearing is also termed as Skewing. ❖ 1. X-Shear ❖ The X-Shear preserves the Y coordinate and changes are made to X coordinates, which causes the vertical lines to tilt right or left as shown in below figure. 5.1.5 SHEAR (CONTN) ❖ 2. Y-Shear ❖ The Y-Shear preserves the X coordinates and changes the Y coordinates which causes the horizontal lines to transform into lines which slopes up or down as shown in the following figure. 5.1.6 HOMOGENOUS TRANSFORMATION To perform a sequence of transformation such as translation followed by rotation and scaling, we need to follow a sequential process – 1. Translate the coordinates, 2. Rotate the translated coordinates, and then 3. Scale the rotated coordinates to complete the composite transformation. To shorten this process, we have to use 3×3 transformation matrix instead of 2×2 transformation matrix. To convert a 2×2 matrix to 3×3 matrix, we have to add an extra dummy coordinate W. In this way, we can represent the point by 3 numbers instead of 2 numbers, which is called Homogenous Coordinate system. In this system, we can represent all the transformation equations in matrix multiplication. Any Cartesian point PX,Y can be converted to homogenous coordinates by P’ (Xh, Yh, h). Computer Gra 5.1.6 HOMOGENOUS TRANSFORMATION (CONTN.) Homogeneous Coordinates Representation: The Rotation can also be represented in the form of 3 x 3 Rotation matrix- Computer Graphics 12 Example - A line segment with the starting point (0, 0) and ending points (5, 5). Apply 30-degree rotation anticlockwise direction on the line. Find the new coordinates of the line? Solution - We can rotate the straight line by its endpoints with the same angle. 5.1.7 COMPOSITE TRANSFORMATION-TRANSLATION If a transformation of the plane T1 is followed by a second plane transformation T2, then the result itself may be represented by a single transformation T which is the composition of T1 and T2 taken in that order. This is written as T = T1∙T2. Composite transformation can be achieved by concatenation of transformation matrices to obtain a combined transformation matrix. A combined matrix − [T][X] = [X] [T1] [T2] [T3] [T4] …. [Tn] Where [Ti] is any combination of Translation, Scaling, Shearing, Rotation, Reflection The change in the order of transformation would lead to different results, as in general matrix multiplication is not cumulative, that is [A] . [B] ≠ [B] . [A] and the order of multiplication. The basic purpose of composing transformations is to gain efficiency by applying a single composed transformation to a point, rather than applying a series of transformation, one after another. For example, to rotate an object about an arbitrary point (Xp , Yp ), we have to carry out three steps − 1. Translate point (Xp , Yp ) to the origin. 2. Rotate it about the origin. 3. Finally, translate the center of rotation back where it belonged. We can represent the coordinates of point A (P0 , Q0 ) by using standard trigonometry

Answer 26

6.WINDOWING AND CLIPPING The method of selecting and enlarging a portion of a drawing is called windowing. The area chosen for this display is called a window. The window is selected by world-coordinate. Sometimes we are interested in some portion of the object and not in full object. So we will decide on an imaginary box. This box will enclose desired or interested area of the object. Such an imaginary box is called a window Viewport: An area on display device to which a window is mapped [where it is to displayed]. Basically, the window is an area in object space. It encloses the object. After the user selects this, space is mapped on the whole area of the viewport. The size of the window is (0, 0) coordinate which is a bottom-left corner and toward right side until window encloses the desired area. Once the window is defined data outside the window is clipped before representing to screen coordinates. This process reduces the amount of data displaying signals. Viewing transformation in several steps First, we construct the scene in world coordinate using the output primitives and attributes. To obtain a particular orientation, we can set up a 2-D viewing coordinate system in the window coordinate plane and define a window in viewing coordinates system. Once the viewing frame is established, are then transform description in world coordinates to viewing coordinates. Then, we define viewport in normalized coordinates (range from 0 to 1) and map the viewing coordinates description of the scene to normalized coordinates. At the final step, all parts of the picture that (i.e., outside the viewport are dipped, and the contents are transferred to device coordinates). Computer Graphics Window to Viewport Co-ordinate Transformation Once object description has been transmitted to the viewing reference frame, we choose the window extends in viewing coordinates and selects the viewport limits in normalized coordinates. Object descriptions are then transferred to normalized device coordinates: We do this thing using a transformation that maintains the same relative placement of an object in normalized space as they had in viewing coordinates. If a coordinate position is at the center of the viewing window: It will display at the center of the viewport. Fig shows the window to viewport mapping. A point at position (xw, yw) in window mapped into position (xv, yv) in the associated viewport. Advantage of Viewing Transformation We can display picture at device or display system according to our need and choice. Note: 1. World coordinate system is selected suits according to the application program. 2. Screen coordinate system is chosen according to the need of design. 3. Viewing transformation is selected as a bridge between the world and screen coordinate. Zooming is a transformation often provided with an imaginary software. The transformation effectively scales down or blows up a pixel map or a portion of it with the instructions from the user. Such scaling is commonly implemented at the pixel level rather than at the coordinates level. A video display or an image is necessarily a pixel map, i.e., a collection of pixels which are the smallest addressable elements of a picture. The process of zooming replicates pixels along successive scan lines. Example: for a zoom factor of two Each pixel value is used four times twice on each of the two successive scan lines. Figure shows the effect of zooming by a factor of 2. Computer Graphics Zooming (contn) Such integration of pixels sometimes involves replication using a set of ordered patterns, commonly known as Dithering. The two most common dither types are: 1. Ordered dither. 2. Random dither. There are widely used, especially when the grey levels (share of brightness) are synthetically generated. Computer Graphics Panning The process of panning acts as a qualifier to the zooming transformation. This step moves the scaled up portion of the image to the center of the screen and depending on the scale factor, fill up the entire screen. Advantage: Effective increase in zoom area in all four direction even if the selected image portion (for zooming) is close to the screen boundary.

Introduction Flashcards

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