Help

[Cyn]

Hi i have an assignment i have to write a program that draws a line across +ve and -ve axes. i used the DDA line algorithm but i don't know how to implement it such that i can draw my line in the -ve quadrants. For the time being My line can only be +ve. Can n e one help me please?

[teknomage1]

Well remember the reason you have an assignement is to learn to solve the problem yourself, but often explaing the problem properly will set things straight in your brain so why don't you explain the problem in more detail, particularly the DDA line algorithm and the ve- and ve+ axes.

[Cyn]

my problem is that i don't know how the code to write if i want my line to be in 2nd, 3rd or 4th quadrant.

[Valmont]

Oh come on. You can do DDA. Even I needed only 2 minutes of study. This is the result:

#include <iostream>

using namespace std;

void DDA(int x1,int y1,int x2, int y2)
{
  int length;
  double x,y;
  double xIncr, yIncr;

  length = abs(x2 - x1);
  if (abs(y2 - y1) > length)
  {
    length = abs(y2 - y1);
  }
  xIncr = (double)(x2 - x1)/(double)length;
  yIncr = (double)(y2 - y1)/(double)length;
  x = x1 + 0.5;
  y = y1 + 0.5;
  while(length)
  {
    cout<<(int)x<<", "<<(int)y<<endl;
    x += xIncr;
    y += yIncr;
    --length;
  }
}

int main(int argc, char *argv[])
{
  DDA(-5, -3, 5, 9);
  
  cin.get();
  return 0;
}