Digital differential analyzer (graphics algorithm): Difference between revisions

Revision as of 18:55, 12 January 2008

Revision as of 19:35, 12 January 2008

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The DDA method is not very efficient due to the need for division and rounding. [[Bresenham's line algorithm]] is a more efficient method to draw lines because it uses only addition, subtraction and bit shifting.

== SampleThe Codealgorithm in code ==

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This is a sample implementation of the DDA implementationalgorithm in the [[C programming language]]:

<pre>

void/* Draw a straight line DDA(intbetween the points (xa, int ya,) intand (xb, int yb) */

void line DDA(int xa, int ya, int xb, int yb) {

{

int dx=xb-xa, dy=yb-ya, steps, k;

floatint xIncrement, yIncrement, xdx=xb-xa,; y=ya;// horisontal difference

int dy=yb-ya; // vertical difference

for(k=0;int k<steps;, k++);

float xIncrement, yIncrement;

float x=xa, y=ya; // the drawing points x and y are initiated to one endpoint of the line

if(abs(dx)>abs(dy))// calculate the number of steps=abs used to draw the line (dxnumber of pixels);

else steps=if(abs(dx)>abs(dy); )

steps=abs(dx);

{else

steps=abs(dy);

// calculate the increment for x and y in each step

xIncrement=dx/(float)steps;

yIncrement=dy/(float)steps;

// point out the starting pixel

setPixel(ROUND(x), ROUND(y));

for(k=0; k<steps; k++)

// loop through the line from one end to the other and point out the pixels

{

for(k=0; k<steps; x k+=+) xIncrement;{

y += yIncrement;

// the points are setPixel(ROUND(x),incremented ROUND(y));an equal amount for every step until the whole line has been drawn

x += xIncrement;

y += yIncrement;

// since the values for x and y are float they are rounded before they are plotted

setPixel(ROUND(x), ROUND(y));

}

}

</pre>

== External links ==