# Compare the angle between several spinning objects
**URL:** https://discourse.processing.org/t/compare-the-angle-between-several-spinning-objects/11194
**Category:** Coding Questions
**Created:** [May 13, 2019, 11:06am UTC](https://discourse.processing.org/t/compare-the-angle-between-several-spinning-objects/11194 "2019-05-13T11:06:32Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@ale.moso](https://discourse.processing.org/u/ale.moso)
#### Post date: [May 13, 2019, 11:06am UTC](https://discourse.processing.org/t/compare-the-angle-between-several-spinning-objects/11194/1 "2019-05-13T11:06:32Z")
Hello dear community,
I made a grid of spinning lines. Now I wonder how to know when a line and is neighbours are matching in the vertical or horizontal axis to change theris colors for that moment in which the share the same position.
Here is the code I have so far for better understanding of what I need to accomplish.
Many thanks in advance!
```auto
Pulsar[] pulsars;
int columns = 5;
int rows = 5;
int total = columns*rows;
float stepX, stepY;
void setup() {
size(500, 500);
strokeWeight(2);
stepX = width/ columns;
stepY = height/ rows;
pulsars = new Pulsar[total];
int index = 0;
for (int j = 0; j < rows; j++) {
for (int i = 0; i < columns; i++) {
// Arrange lines in a grid
pulsars[index] = new Pulsar(i * stepX + (stepX/2), j * stepY + (stepY/2));
// update counter
index ++;
//reset counter
if (index == total) index = 0;
}
}
}
void draw() {
background(10);
int index = 0;
for (int j = 0; j < rows; j++) {
for (int i = 0; i < columns; i++) {
// new velocity for every line
float vel = (index + 1) * 0.003;
stroke(255);
pulsars[index].display(vel);
// update counter
index ++;
//reset counter
if (index == total) index = 0;
}
}
}
// ROTATING OBJECT
class Pulsar {
float posX, posY, vel;
float angle = 0;
Pulsar(float posX_, float posY_) {
posX = posX_;
posY = posY_;
}
void display(float vel) {
pushMatrix();
translate(posX, posY);
rotate(angle);
// draw forms
ellipse(0, 0, 4, 4);
line(-width/(rows*2), 0, height/(rows*2), 0);
// uopdate angle
angle += vel;
popMatrix();
}
}
```
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### Author:  [@kll](https://discourse.processing.org/u/kll)
#### Post date: [May 13, 2019, 11:45am UTC](https://discourse.processing.org/t/compare-the-angle-between-several-spinning-objects/11194/2 "2019-05-13T11:45:29Z")
[http://www.jeffreythompson.org/collision-detection/line-line.php](http://www.jeffreythompson.org/collision-detection/line-line.php) ;
but that requires that you know where the lines are!
so instead working with
push / translate / rotate / line(x1,y1,x2,y2) / pop
better work with array for x1,y1,x2,y2 and calculate/fill that by some math first.
( just a idea )
---
### Author:  [@ale.moso](https://discourse.processing.org/u/ale.moso)
#### Post date: [May 13, 2019, 1:52pm UTC](https://discourse.processing.org/t/compare-the-angle-between-several-spinning-objects/11194/3 "2019-05-13T13:52:16Z")
I was hoping that using the angle rotation were the soulution but the more I think it the more I see is a nonsense.
How many arrays you think I would need? A 2D array like this [[x1, y1, x2, y2], [x3, y3, x4, y4] … ] would be enough?
Thank you @kll!
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### Author:  [@ale.moso](https://discourse.processing.org/u/ale.moso)
#### Post date: [May 13, 2019, 2:10pm UTC](https://discourse.processing.org/t/compare-the-angle-between-several-spinning-objects/11194/4 "2019-05-13T14:10:29Z")
Another question is if I can’t use rotate or any transformation function, cause this wouldn’t works with collision detection, how cant y make them spin?