Straight line

Question

          if (mousecounter == 0)
          slope = (newx-oldx)/(newy-oldy);
          slope2 = (newy-oldy)/(newx-oldx);
          ++mousecounter;
oldx = oldx+ slope;
oldy = oldy + slope2;I need desperate.......... I need to be able to take the old coordinates (oldx. oldy) and move them in straight line to (newx, newy). The problem is, its a mouse click, and it will need to be able to move forward, backward, side to side, etc in a straight line...... Suggestions?

Answer 1

Did you figure out your other problem (with getting x or y always 0)?
Anyway, your slope should be the same for changing both x and y coordinates. Why do you have two slopes? You can't add slopes to x or y coordinates--that makes no sense.
You have an object at (oldx, oldy).
The user clicks on (newx, newy).
The line between the points is:
(y-oldy)/(x-oldx) = (newy - oldy)/(newx - oldx)Or (expressing y in terms of x):
y = (((newy - oldy)/(newx - oldx))*(x - oldx)) + oldyOr:
y = (((newy - oldy)/(newx - oldx))*(x)) + (oldy - ((newy - oldy)/(newx - oldx))*oldx)If you pick an x, you can calculate the matching y on that line. To move in n steps:
x = oldx;
x_n = oldx + (((newx - oldx)/n) * oldx);Put those x values in the equation for y, and you will get the corresponding y. Of course, you could just do the same as you did for x:
y = oldy;
y_n = oldy + (((newy - oldy)/n) * oldy);