1. CSI 421: Computer Graphics
CSI 421: Computer Graphics |

2. CSI 421: Computer Graphics | saleh.sabbir.aiub@gmail.com

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4. CSI 421: Computer Graphics | saleh.sabbir.aiub@gmail.com

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9. CSI 421: Computer Graphics | saleh.sabbir.aiub@gmail.com

10. CSI 421: Computer Graphics | saleh.sabbir.aiub@gmail.com10

11. MNE P=(xp, yp) is pixel chosen by the algorithm in previous step
To calculate d incrementally we require dne w
If d > 0 then choose NE
If d < 0 then choose E ( x + 1, y + )
( x + 2, y + 3 )
p 2 1
p 2
MNE NE M yp E
P=(xp, yp)
xp xp+1
xp+2
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CSI 421: Computer Graphics |

12. CSI 421: Computer Graphics | saleh.sabbir.aiub@gmail.com

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15. CSI 421: Computer Graphics | saleh.sabbir.aiub@gmail.com

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17. CSI 421: Computer Graphics | saleh.sabbir.aiub@gmail.com

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19. CSI 421: Computer Graphics | saleh.sabbir.aiub@gmail.com

20. The most common side effects when working with raster devices are:
Aliasing
Unequal intensity
Overstrike
Picket fence problem
CSI 421: Computer Graphics |

21. Consider equation y = mx + b For m = 0.5, b = 1 and x = 3 : y = 2.5
Refers to the plotting of a point in a location other than its true location in order to fit the point into the raster.
Consider equation y = mx + b
For m = 0.5, b = 1 and x = 3 : y = 2.5
So the point (3,2.5) is plotted at alias location (3,3) Remedy
Apply anti-aliasing algorithms. Most of these algorithms introduce extra pixels and pixels are intensified proportional to the area of that pixel covered by the object.
CSI 421: Computer Graphics |

22. CSI 421: Computer Graphics | saleh.sabbir.aiub@gmail.com

23. Human perception of light is dependent on
Density and
Intensity of light source. 1
Thus, on a raster display with perfect squareness, a diagonal line of pixels will appear dimmer that a horizontal or vertical line.
Remedy
If speed of scan conversion is main then ignore
By increasing the number of pixels in diagonal lines
By increasing the intensity of pixels on diagonal lines.
CSI 421: Computer Graphics |

24. The same pixel is written more than once.
This results in intensified pixels in case of photographic media, such as slide or transparency
Remedy
Check each pixel to see whether it has already been written to prior to writing a new point.
CSI 421: Computer Graphics |

25. Occurs when a user attempts to scan-convert an object that will not fit exactly in the raster.
Original Object
Local aliasing
Global aliasing
Remedy
Local Aliasing: the distances between pickets in the picket fence will be kept as close to their true relative distance as possible
Global Aliasing: the overall length of the picket fence will be approximately correct by the spacing between pickets will be distorted.
CSI 421: Computer Graphics |

26. Must Read: Optional: References: •Ellipse: Scan conversion
•Region filling algorithms
•Point conversion
•DDA algorithm
•Bresenham’s Algorithm
•Solved problems ( )
References:
Text book – chapter 3
Wikipedia and google with topic name
CSI 421: Computer Graphics |