Page 30 - Computer Graphics

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Digital Differential Analyzer Algorithm

{
dx=x2 - x1

dy=y2 - y1

if(abs(dx) > abs(dy))

step abs(dx)

else

step abs(dy)

x inc = dx/step

y inc = dy/step

for(i=1 ; i<=step ; i++)

put pixel (x1 , y1)

x1=x1 + x inc

y1=x1 + y inc

}

1. The DDA algorithm is a faster method for calculating pixel positions
2. Appropriate increments are applied in the x or y direction to step to pixel
positions along the line path
3. We consider more general scan-line procedures that can be applied to both

lines and curves