Making my float increase then decrease so that my ellipses grows and then shrinks

Processing Coding Questions
1

Here is the code I use to make ellipses grow and then shrink. I have already declared vision as a float with the starting value 0;


  if (circleIsShrinking) vision = vision -0,2;
  else vision = vision +0,2;
  
 
  if (vision == 0 || vision == 150) circleIsShrinking = !circleIsShrinking;
			
		print (vision);

I also tried

if (vision < 0 || vision > 150) circleIsShrinking = !circleIsShrinking;

but it does not work.
In both cases the vision does not even start to increase in size

1 Like
2

If you increment and decrement by 0.2 you might never get exactly 0 or 150. A good paper to read about this is What Every Computer Scientist Should Know About Floating-Point Arithmetic.

3 Likes
3

I did take that into consideration so I used the < and > once too but it did not work either

4

Wait, you’re using “-0,2” and “+0,2” with commas between the digits? I don’t think that will work because Java and therefore Processing wants you to use periods to separate the whole part of a number from the fractional part of a number. So in essence your code is adding “+0” or “-0” to vision instead of 2 tenths.

1 Like
5

I dont completely understand. You said im adding 0 to vision, so how do I add 0,2 instead?

6

Use “0.2” or “-0.2” not “0,2” or “-0,2”

3 Likes
8

@Kenga123456 hi

something like this ?

int inc = 1;
int x =0; 
void setup() { 
  size(600, 600);
  ellipseMode(CENTER);
} 
void draw() { 
  background(222); 
  x= x + inc; 
  fill(0,0 , 222);
    ellipse(300, 300, x, x); 
  if (x >= 400|| x <= 0 ) { 
    inc = inc * -1;
  }
}
9

Yup that worked, though I also had to fix some problems within the entire program first. Thank you!

1 Like