Formula does work on paper however not in my very simple program

Processing Beginners
1

I’m running into an issue where it seems like processing is wrongly calculating my formulas.

The idea is simple I draw a line and I want to draw n number of points on that line, evenly distributed.

So I came up with a formula that calculates the x and y locations of the points along this line which in a calculator works fine however not in my program.

x = starting point of line
x1 = end point of line
xCheck = the to be calculated point along the line
n = number of points
i = how many iterations of the for loop

(x/ni)+(x1/n(n-i)) = x2

int x = floor(random(0,width));
  int y = floor(random(0,height));
  int x1 = floor(random(0,width));
  int y1 = floor(random(0,height));
  
  int n = 5;

  size(800,800);
  stroke(0);
  fill(255,0,0);
  line(x,y,x1,y1);
  println(x,y,x1,y1);
  println(" ");
  
  for(int i = 0; i <= n; i++){
    float xCheck = (x/n*i)+(x1/n*(n-i));
    float yCheck = (y/n*i)+(y1/n*(n-i));
    noStroke();
    ellipse(xCheck,yCheck,4,4);
    print(xCheck,yCheck + "   ");
  }

The result is that the points are always a few pixels off around(1 - 5)
Does anyone perhaps understand what exactly I am doing wrong here?

EDIT:
It also seems that the bigger the number n is, the bigger the offset of the points is. The reason for this I do not undertsand

2

Hello,

Change your variable declarations from int to float and see what happens.

More importantly, understand what is happening.

Look up integer division .

https://www.youtube.com/watch?v=ql3G1ZSe098

image
image386×523 15.9 KB

``:)

1 Like
3

Hello @Nino
Also, computers use the binary number system (or base-2) and not the decimal number system (or base-10). So the inaccuracy is inherent with these two number systems not seamlessly aligning.
:nerd_face:

4

Extremely sorry for the late reply I had forgotten about the forum for a bit.
Your answer helped me a lot! I did my look into integer maths and understand why it wasn’t working now.
Thanks a lot!

1 Like