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PCTI Group. Computer Graphics By : Pcti Group. Session 1:. The Coverage: Introduction Conceptual Framework Interactive and Passive Graphics. Computer Graphics.

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## PCTI Group

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**PCTI Group**Computer Graphics By : Pcti Group**Session 1:**The Coverage: • Introduction • Conceptual Framework • Interactive and Passive • Graphics. Presentation Title | October 4, 2014 | <document classification>**ComputerGraphics**Computer Graphics is the Intermediary between the Application Model[program] and display HARDWARE that effects an output transformation from the objects In the application model to view of the model. Presentation Title | October 4, 2014 | <document classification>**Graphics**System Application Model Application Program Display Device/PC Conceptual framework for Interactive Graphics: Presentation Title | October 4, 2014 | <document classification>**InteractiveGraphics:**As per the framework, a computer receives input from interaction devices, and output images to a display device.The S/W has 3 components: 1.Application Program: It Creates,Stores, and retrieves from the third Component, which is Graphics System. 2.Graphics System: This is responsible for actually producing the picture from the detailed descriptions. 3.Display Hardware: The actual HARDWARE device. Presentation Title | October 4, 2014 | <document classification>**Passive Graphics**A Computer Graphics Operation that transforms automatically and Without operator intervention. Presentation Title | October 4, 2014 | <document classification>**User Interfaces**Interactive plotting in business,Science and Technology. Office automation and E-Publishing. CAD and CAM application. Simulation. Art and Commerce. Process Control. Cartography. Usage of Computer Graphics: Presentation Title | October 4, 2014 | <document classification>**Display Devices:**• Refresh CRT. • Random and Raster Scan Monitor. • Color CRT Monitors. • Direct View Storage Tubes(DVST). • Flat Panel Displays. • Light Emitting Diodes and LCD’s. • Hard Copy Devices. Presentation Title | October 4, 2014 | <document classification>**Session -2**The Coverage: * Refresh CRT. * Deflection. MAGNETIC ELECTRONIC DEFLECTION Raster and Random Scan Displays. * Presentation Title | October 4, 2014 | <document classification>**Focussing Anode**Electron Beam Path. Cathode Accelerating Anode Control Grid Display Screen. Refresh CRT: Presentation Title | October 4, 2014 | <document classification>**Electrostatic deflection of the electron beam in a CRT.**Phosphor Screen Focussing System Vertical Deflection Plates Base Connector pins Horizontal Deflection Plates Electron Beam Presentation Title | October 4, 2014 | <document classification>**Random Scan System**A Random scan system draws the Component lines of an object in any order Specified. Presentation Title | October 4, 2014 | <document classification>**Raster Scan System**A Raster Scan system displays an Object as a set of discrete points Across each scan lines. Presentation Title | October 4, 2014 | <document classification>**Interlacing**In Some raster scan Systems(TV sets etc.) each frame is displayed into passes using an interlaced refresh procedure.In first pass, the beam sweeps across every other scan line from top to bottom.Then after the vertical retrace, the beam sweeps out the remaining scan lines. Interlacing of the scan lines allows us to see the entire screen displayed in one half of the time and used with SLOWER REFRESHING RATES. With Interlacing , each of the two passes can be accomplished in 1/60th of a second.which brings the refresh rates nearer to 60 frames/second. This is the effecting Technique for avoiding flicker. Presentation Title | October 4, 2014 | <document classification>**Session 3:**The Coverage: • Color CRT. • Shadow Masking. • DVST. • LED. • LCD. Presentation Title | October 4, 2014 | <document classification>**Color CRT Monitors**A CRT Monitors displays color pictures by using a combination of phosphorus that emit different colored light. By this , a range of different color displays with CRT are the beam penetration method and shadow Masking. Beam penetration method has been used with a random scan monitors.Two layers of phosphor,red and green are coated onto the inside of the CRT SCREEN and the displayed Color depends on how far the electron beam penetrates into the phosphor layers. Its an inexpensive way to produce color in random scan monitors and qualities of pictures is not as Good as with other Methods. A Presentation Title | October 4, 2014 | <document classification>**Selection Of shadow Masking**red Magnified Phosphor-Do Triangle green blue screen Shadow Masking Electron Guns Presentation Title | October 4, 2014 | <document classification>**Direct -View Storage Tubes**An alternative method for maintaining a screen image is to store the picture the picture information inside the CRT instead of refreshing the screen. A direct View Storage Tube(DVST) stores the picture information as a charge distribution just behind the phosphor-coated screen.Two Electron guns are used in a DVST. One ,the primary gun, is used to store the picture pattern;the second,the flood gun,maintain the picture display. They Don’t display colors and that selected parts of a picture cannot be erased. To eliminate a picture,the entire screen must be erased and the modified picture redrawn. The erasing and redrawing process can take several seconds for a complex picture. Presentation Title | October 4, 2014 | <document classification>**Light Emitting Diodes**A third type of emissive device is the Light Emitting Diode.A matrix Of diode is arranged to form the pixel positions in the display, and the Picture definitions is stored in a refresh buffer.As in scan line refreshing of a CRT, information is read from the Refresh Buffer and converted to voltage levels that are applied to the diodes to Produce the light patterns in the display. Presentation Title | October 4, 2014 | <document classification>**Liquid Crystal Display**Commonly used in small systems ,such as calculators and computers.These non emissive devices produce a picture by Passing polarized light from the surroundings or from an Internal light source through a liquid crystal material that can Be aligned to either block or transmit signals (light). Presentation Title | October 4, 2014 | <document classification>**Session 4:**The Coverage: *Introduction of Scan conversion. *Scan about a point. *Scan about a line. Presentation Title | October 4, 2014 | <document classification>**Scan Conversion**Introduction Scan Converting About • a POINT. • a LINE. • a CIRCLE. • an ELLIPSE. Side effects of Scan Conversion Presentation Title | October 4, 2014 | <document classification>**Introduction**Many scan conversion algorithms are implemented in computer hardware or firmware. However a specific graphic algorithm can be implemented in software. The most common used graphics Objects are the line,the sector,arc,the ellipse,The rectangle and the polygon. * We will assume that all objects lie within the Boundaries of the display device coordinate system. Presentation Title | October 4, 2014 | <document classification>**Scan Converting a point**A mathematical point(x,y) where x and y are the real numbers within an image area, needs to be scan converted to a pixel at location(x’,y’) y Pixel Grid y Pixel grid 3.0 P3(2.8,1.9) P3(2.8,1.9) 2 P2(2.2,1.3) 2.0 P2(2.2,1.3) 1.0 1 P1(1.7,0.8) P1(1.7,0.8) x x 0 Pixel Coordinates 0.0 2.0 3.0 Pixel Coordinates 0 3 1.0 1 2 Scan Converting Point Presentation Title | October 4, 2014 | <document classification>**Scan Converting a Scan Lines**A straight line may Be defined by two endpoints and an equation.The two End Points are described by(x1,y1) and (x2,y2).The equation of the line is used to describe the x,y coordinates of all the points that lie between these two endpoints. y (X2,y2) Y X (X1,y1) x The Straight Line Presentation Title | October 4, 2014 | <document classification>**Session 5:**The Coverage: *Introduction To Line Drawings: DDA Algorithm BRESENHAM’S Algorithm. Presentation Title | October 4, 2014 | <document classification>**Bresenham's Line Algorithm**Bresenham's line algorithms is a highly efficient method for scan -converting lines.It produces mathematically accurate results using only integer addition,subtraction and multiplication by 2,which can be done by simple arithmetic shift operation. Scan-Converted Points y Yi+1 T t Yi s True Line S P1 x Xi+1 Xi Presentation Title | October 4, 2014 | <document classification>**DDA line Algorithm**DDA OR DIGITAL DIFFERENTIAL ANALYZER ALORITHM IS AN INCREMENTAL SCAN-CONVERSION METHOD.THIS APPROACH IS CHARACTERIZED BY PERFORMINGCALCULATIONS AT EACH STEP RESULTS FROM THE PRECEDING STEP. SUPPOSE at step I we have to calculated(Xi,Yi) to be point on the line.Since the next POINT on the line is (Xi+1,Yi+1) should satisfy delta y/delta x = m where delta Yi+1 –Yi and delta x = Xi+1 –Xi ,we have Yi+1 = Yi +m.delta X OR Xi+1 = Xi +delta/m The DDA algorithm is faster than the direct use of line equation since it calculates Point the line with out any floating –point manipulation. However, a floating point addition still needed in determining each successive point.Furthermore, cumulative error due to limited precision in the floating point representation. May cause calculated points to draft away from their true position when the line is Relatively long. Presentation Title | October 4, 2014 | <document classification>**Session 6:**The Coverage: *Scan Conversion of a Circle *Defining a Circle. Presentation Title | October 4, 2014 | <document classification>**Scan Converting a Circle**A Circle is the Symmetrical Figure. Any Circle Generating algo take advantage of the circle’s Symmetry to plot eight points for each value that the algorithm calculates. Eight way symmetry is used by reflecting each calculated points around each 45 degree axis. y (-Y,X) 3 (Y,X) 2 5 4 (-X,Y) 3 4 1 (X,Y) 2 1 x 1 3 2 4 (-x,-y) 5 8 (x,-y) 6 7 (-y,-x) (y,-x) Presentation Title | October 4, 2014 | <document classification>**Defining a Circle**y y P=(Xi P= (r cos r 2 2 , Sin r x r y rcos x x rcos x Circle defined with a second –egree Polynomial equation. Circle defined with trigonometric functions Presentation Title | October 4, 2014 | <document classification>**Session: 7**The Coverage: *Scan Conversion of Ellipse. *Side Effects. Presentation Title | October 4, 2014 | <document classification>**Scan -Converting an Ellipse**The ellipse , like the circle,shows Symmetry.In the case of an ellipse,how ever,Symmetry is four rather than eight-way. There are two Methods of mathematically Defining an ellipse. PLOYNOMIAL METHOD OF DEFINING AN ELLIPSE: The polynomial method of defining an ellipse is given by the (X-h) 2 2 (Y-k) = 1 Where (h,k) ellipse center a= length of major axis. B= length of minor axis. 2 2 a b When the polynomial method is used to define an ellipse,the value of x is added From h to a. For each step of x,each value of y is found by evaluating the expression. Y = b 2 x - h + k 1 - 2 a This method is very efficient,However, because the squares of a and (x-h) must be Found. Then floating point division of (x - h) 2 By a And floating point Multiplication of the square root [1 –(x-h) ] By b. Presentation Title | October 4, 2014 | <document classification>**Side Effects of Scan Conversion**1.ALIASING 2.Overstrike Presentation Title | October 4, 2014 | <document classification>**Session: 8**The Coverage: • Transformations. • Transformation Types. • Geometric Transformation. Presentation Title | October 4, 2014 | <document classification>**2D Graphics Transformation**Introduction: The object of 2D Graphics Transformation is to describe there operations in mathematical form suitable for computer processing and how they are used to achieve the Ends of object manipulation and motion. Presentation Title | October 4, 2014 | <document classification>**Transformation Types:**• Geometric Transformation • Coordinate transformation • Composite Transformation Presentation Title | October 4, 2014 | <document classification>**Geometric Transformation**p ‘ Object y y Object p 0 x 0 x Under This ,An Object in the plane can be considered as set of points.Every object Point p has Coordinates (X,Y) and so the object is the sum total of all of its Coordinate points. If the object is moved to a new Position, it can be regarded as New Object Obj’, all of whose coordinate point P’ can be obtained from the original P by the application of a geometric transformation. Presentation Title | October 4, 2014 | <document classification>**Session: 9**The Coverage: *Coordinate Transformation. *Composite Transformation. * Concatenation of matrices. Presentation Title | October 4, 2014 | <document classification>**Coordinate Transformation**Y’ Y O’ X’ Y P(x,y)(x’,y’) X O We have two coordinate Systems in the plane.The First System is located at the Origin O and has coordinate axes XY .The Second Coordinate System is located at origin O’ and has Coordinate axes x’y’ .Now each point in the Plane has two coordinate descriptions (x,y) and (x’,y’),depending upon which Coordinate System is used.IT MEANS THE TRANSFORMATION ARISING FROM A TRANSFORMATION APPLIED TO THE FIRST SYSTEM X,Y ,WE CAN SAY THAT A COORDINATE TRANSFORMATION HAS BEEN APPLIED. Presentation Title | October 4, 2014 | <document classification>**Composite Transformation**The More complex geometricand coordinate transformations can be built from the basic transformations by using the process of composition of functions. Here the basic transformation of rotation[displacement of objects Scaling and the reflection can be represented as matrix functions. Geometric Transformations Coordinate Transformations Cos Cos R -Sin Sin = R cos cos sin - sin S = S S . S 0 = X S S 1 Y . S 0 X X Y X 0 S 1 0 S Y Y Presentation Title | October 4, 2014 | <document classification>**Concatenation Of Matrices**The advantage of introducing a matrix from for translation is that we can now build complex transformation by multiply the basic matrix transformations.This process is sometimes called concatenation of matrices.We must be able to represent the basic transformations as 3*3 homogeneous coordinate matrices so as to be compatible with the matrix of translation. Presentation Title | October 4, 2014 | <document classification>**Session: 10**The Coverage: • Viewing and clipping. • Window to view port Mapping. Presentation Title | October 4, 2014 | <document classification>**2D Viewing & Clipping**World coordinate System: Much Like what we see in real life through a small window on the wall or the viewfinder or camera, a computer generated image often depicts a partial view of a large scene.Objects are placed into the scene by modeling transformations to a master coordinate System called as WORLD COORDINATE SYSTEM. A rectangular window with its edge parallel the axes of the WCS is used to select the portion of the scene for which an image is to be generated. Workstation Window Workstation Viewport 1 Viewport 1 0 World Coordinate System 0 Presentation Title | October 4, 2014 | <document classification>**Window To View port Mapping**Objective: The Objective of window -to -viewport mapping is to convert the world coordinates(wx,wy) of arbitrary point to its corresponding normalized device coordinates(vx,vy). VIEWPORT WINDOW wy vy vy wy 0 1 vy wx wx 0 vy Presentation Title | October 4, 2014 | <document classification>**Session: 11**The coverage: • Cohen Sutherland algorithm. • Introduction to Interactive Graphics. Presentation Title | October 4, 2014 | <document classification>**Cohen Sutherland Algorithm**Under this, we divide the LINE CLIPPING PROCESS into two phases: 1.Identify those lines which intersects the clipping window and so need to be clipped and, 2.Performed the clipping. All lines fall into one of the following clipping categories: 1.Visible:Both endpoints of the line within window 2.Not Visible:The line definitely lies outside the window.This will occur if the line from(x1,y1)to(x2,y2)satisfies any one of the following four inequalities. X1,X2>Xmax y1,Y2>ymin X1,X2<Xmin Y1,Y2<Ymin 3.Clipping Candidate: The line is neither 1 or 2. Presentation Title | October 4, 2014 | <document classification>**Pictorial View: Coheb Sutherland Algorithm**Presentation Title | October 4, 2014 | <document classification>**Interactive Graphics:**There are commonly interactive graphics devices are as follows: 1.Key-Board. 2.TOUCH PANELS. 3.Light Pen. 4.Graphics Tablet. 5.Joystick. 6.Mouse. 8.Voice System. Presentation Title | October 4, 2014 | <document classification>**Session: 12**The Coverage: • Interactive Graphics Techniques. * Introduction of GKS. Presentation Title | October 4, 2014 | <document classification>

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