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Digital differential analyzer (graphics algorithm): Difference between revisions

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→Program: The DDA algorithm requires rounding the floating point x,y to the nearest integer. The sample code should not depend on the behavior of some specific graphics library's putpixel() (for example if it takes int parameters, float->int uses truncation and will produce the wrong answer)
 
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{{short description|Hardware or software used for interpolation of variables over an interval}}
{{About|a graphics algorithm|the digital implementation of a differential analyzer|Digital differential analyzer}}
 
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:<math>m = \frac{y_{\rm end} -y_{\rm start}}{x_{\rm end}-x_{\rm start}}</math>
 
In fact any two consecutive points (x,y) lying on this line segment should satisfy the equation.
 
== Performance ==
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The [[Fixed-point arithmetic|fixed-point]] integer operation requires two additions per output cycle, and in case of fractional part overflow, one additional increment and subtraction. The probability of fractional part overflows is proportional to the ratio m of the interpolated start/end values.
 
DDAs are well suited for hardware implementation and camhgncan be pipelined for maximized throughput.
 
== Algorithm ==
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== Program ==
DDA algorithm Programprogram in Turbo [[C++]]:
 
<syntaxhighlight lang="c++cpp" line="1">
#include <graphics.h>
 
#include <iostream.h>
#include <math.h>
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#include <conio.h>
 
void main( )
{
float x,
float y,
float x1, y1,
float x2, y2, dx, dy, step;
int i, gd = DETECT, gm;
initgraph(&gd, &gm, "C:\\TURBOC3\\BGI");
cout << "Enter the value of x1 and y1 : ";
cin >> x1 >> y1;
cout << "Enter the value of x2 and y2: ";
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dx = (x2 - x1);
dy = (y2 - y1);
 
if (abs(dx) >= abs(dy))
step = abs(dx);
else
step = abs(dy);
 
dx = dx / step;
dy = dy / step;
x = x1;
y = y1;
i = 10;
 
while(i <= step) {
while putpixel(x,i y,<= 5step); {
putpixel(round(x), round(y), 5);
x = x + dx;
y = y + dy;
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delay(100);
}
 
getch();
closegraph();
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* [[Bresenham's line algorithm]] is an algorithm for line rendering.
* [[incrementalIncremental error algorithm]]
* [[Xiaolin Wu's line algorithm]] is an algorithm for line anti-aliasing
 
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[[Category:Computer graphics algorithms]]
[[Category:Digital geometry]]
[[Category:Articles with example C++ code]]
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