The document discusses the Digital Differential Analyzer (DDA) line drawing algorithm. It begins with an introduction to DDA and how it is used to draw lines on a computer screen. It then covers the understanding, procedure, practice problems, advantages, limitations, and conclusion of the DDA algorithm. The core steps of the DDA algorithm include calculating delta X and Y values and the slope between starting and ending points, determining the number of steps, and generating new points along the line through rounding until the ending point is reached. While simple to implement, DDA has limitations such as a lack of smoothness from rounding, but remains a useful basic line drawing technique.

1. WELCOM
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2. Presentation Topic:
DDA (Digital Differential Analyzer )
Line Drawing Algorithm

3. Table of Content
 Introduction
 Understanding The Algorithm
 Procedure
 Practice Problems Based On DDA Algorithm
 Advantages
 Limitations
 Conclusion

4. Introduction
 The line (vector) generation algorithms which determine the
pixels that should be turned ON are called as digital
differential analyzer (DDA).
 It is a simple and efficient algorithm used to draw lines on a
computer screen.
 It is one of the technique for obtaining a rasterized straight
line.
 This algorithm can be used to draw the line in all the
quadrants.
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5. Understanding The Algorithm
 DDA Algorithm is the simplest line drawing algorithm.
 Given the starting and ending coordinates of a line, DDA
Algorithm attempts to generate the points between the
starting and ending coordinates.
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6. Procedure
Given-
 Starting coordinates = (X0, Y0)
 Ending coordinates = (Xn, Yn)
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7. Procedure (Cont.)
• Step-01:
• Calculate ΔX, ΔY and M from the given input.
• These parameters are calculated as -
 ΔX = Xn – X0
 ΔY =Yn – Y0
 M = ΔY / ΔX
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8. Procedure (Cont.)
• Step-02:
• Find the number of steps or points in between the starting and
ending coordinates.
if (absolute (ΔX) > absolute (ΔY))
Steps = absolute (ΔX);
else
Steps = absolute (ΔY);
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9. Procedure (Cont.)
• Step-03:
• Suppose the current point is
(Xp, Yp) and the next point is
(Xp+1, Yp+1).
• Find the next point by
following the below three cases-
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10. Procedure (Cont.)
• Step-04:
• Keep repeating Step-03 until the end point is reached or the
number of generated new points (including the starting and
ending points) equals to the steps count.
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11. Practice Problems Based On DDA Algorithm
• Problem-01:
• Calculate the points between the starting point (5, 6) and
ending point (8, 12).
• Solution-
• Given-
 Starting coordinates = (X0, Y0) = (5, 6)
 Ending coordinates = (Xn, Yn) = (8, 12)
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12. Practice Problems Based On DDA Algorithm
(cont.)
• Step-01:
• Calculate ΔX, ΔY and M from the given input.
• ΔX = Xn – X0 = 8 – 5 = 3
• ΔY =Yn – Y0 = 12 – 6 = 6
• M = ΔY / ΔX = 6 / 3 = 2
• Step-02:
• Calculate the number of steps.
• As |ΔX| < |ΔY| = 3 < 6, so number of steps = ΔY = 6
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13. • Step-03:
• As M > 1, so case-
03 is satisfied.
• Now, Step-03 is
executed until Step-
04 is satisfied.
Xp Yp Xp+1 Yp+1
Round off
(Xp+1, Yp+1)
5 6 5.5 7 (6, 7)
6 8 (6, 8)
6.5 9 (7, 9)
7 10 (7, 10)
7.5 11 (8, 11)
8 12 (8, 12)
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Practice Problems Based On DDA Algorithm
(cont.)

14. 14
Practice Problems Based On DDA Algorithm
(cont.)

15. Advantages
The DDA algorithm is straight-forward to implement.
It only requires basic arithmetic operations like addition
and division.
It can be used to draw lines in both positive and
negative slopes.
DDA draws the line faster than drawing the line by
directly using the line equation.
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16. Limitations
 There is an extra overhead of using round off( ) function.
 Using round off( ) function increases time complexity of the
algorithm.
 Resulted lines are not smooth because of round off( )
function.
 The points generated by this algorithm are not accurate.
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17. Conclusion
 The DDA line drawing algorithm is a simple and widely
used method to draw lines on raster displays.
 While it has its limitations, it remains a valuable tool for
many applications.
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18. Thank You
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