dda algorithm-cg.pptx

dda algorithm-cg.pptx

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  COMPUTER GRAPHICS BY MS. N.RUBA ASST.PROF/ CA BSCW, THANJAVUR.
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  ❑ Graphics aredefined as any sketch or a drawing or a special network that pictorially represents some meaningful information. ❑ Computer Graphics is used where a set of images needs to be manipulated or the creation of the image in the form of pixels and is drawn on the computer. ❑ Computer Graphics can be used in digital photography, film, entertainment, electronic gadgets, and all other core technologies which are required. It is a vast subject and area in the field of computer science. ❑ Computer Graphics can be used in UI design, rendering, geometric objects, animation, and many more. ❑ In most areas, computer graphics is an abbreviation of CG. INTRODUCTION TO COMPUTERGRAPHICS
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  POINTS : ❑ APoint in three-dimensional geometry is defined as a location in 3D space that is uniquely defined by an ordered triplet (x, y, z) where x, y, & z are the distances of the point from the X-axis, Y-axis, and Z-axis respectively. POINTS AND LINES
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  ❑ A Linein three-dimensional geometry is defined as a set of points in 3D that extends infinitely in both directions and is represented by L : (x – x1) / l = (y – y1) / m = (z – z1) / n; here (x, y, z) are the position coordinates of any variable point lying on the line, (x1, y1, z1) are the position coordinates of a point P lying on the line, and l, m, & n are the direction ratios (DRs). ❑ In 3D a line is also formed by the intersection of two non-parallel planes. LINES :
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  LINE-DRAWING ALGORITHMS ❑ “TheLine drawing algorithm is a graphical algorithm which is used to represent the line segment on discrete graphical media, i.e., printer and pixel-based media.” ❑ A line contains two points. The point is an important element of a line. Algorithms of Line Drawing There are following algorithms used for drawing a line: □ DDA (Digital Differential Analyzer) Line Drawing Algorithm □ Bresenham’s Line Drawing Algorithm □ Mid-Point Line Drawing Algorithm
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  DDA ALGORITHM ❑ DDAstands ly zer .It is an incremental method of scan conversion of line. In this method calculation is performed at each step but by using results of previous steps. ❑ Suppose at step i, the pixels is (xi,yi) The line of equation for step i yi=mxi+b......................equation 1 Next value will be yi+1=mxi+1+b.................equation 2 m = yi+1-yi=∆y.......................equation 3 yi+1-xi=∆x......................equation 4 yi+1=yi+∆y ∆y=m∆x yi+1=yi+m∆x ∆x=∆y/m xi+1=xi+∆x xi+1=xi+∆y/m
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  □ This algorithmis used for scan converting a line. It was developed by Bresenham. □ It is an efficient method because it involves only integer addition, subtractions, and multiplication operations. □ These operations can be performed very rapidly so lines can be generated quickly. BRESENHAM’S LINE ALGORITHM
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  PARALLEL LINE ALGORITHMS ❑A parallel algorithm is an algorithm that can execute several instructions simultaneously on different processing devices and then combine all the individual outputs to produce the final result.
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  LOADING THE FRAMEBUFFER □ A frame buffer is a large, contiguous piece of computer memory. At a minimum there is one memory bit for each pixel in the rater; this amount of memory is called a bit plane. The picture is built up in the frame buffer one bit at a time. □ You know that a memory bit has only two states, therefore a single bit plane yields a black-and white display. □ You know that a frame buffer is a digital device and the CRT is an analog device. □ Therefore, a conversion from a digital representation to an analog signal must take place is read from the frame buffer and displayed on the raster when information CRT graphics device. □ For this you can use a digital to analog converter (DAC). □ Each pixel in the frame buffer must be accessed and converted before it is visible on the raster CRT.