# How to add a trail particle effect to a moving circle?

**URL:** <https://discourse.processing.org/t/how-to-add-a-trail-particle-effect-to-a-moving-circle/5967>\
**Category:** Coding Questions\
**Created:** [November 26, 2018, 6:38pm UTC](https://discourse.processing.org/t/how-to-add-a-trail-particle-effect-to-a-moving-circle/5967 "2018-11-26T18:38:02Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![francium401](https://avatars.discourse-cdn.com/v4/letter/f/977dab/32.png) [@francium401](https://discourse.processing.org/u/francium401)\
**Post date:** [November 26, 2018, 6:38pm UTC](https://discourse.processing.org/t/how-to-add-a-trail-particle-effect-to-a-moving-circle/5967/1 "2018-11-26T18:38:02Z")

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Basically what I have here is a circle orbiting another (very tinier) circle.  
What I’ve been trying to figure out is how to add a trail particle effect to the orbiting circle, where the end of the trail fades from white to being transparent.

My end goal is to try and duplicate these rotating circles in different positions to make them look like star trails:

 ![Blog2_StarTrails_316x30sec_158min_iso800_32mm_5D_sml](https://canada1.discourse-cdn.com/flex036/uploads/processingfoundation1/original/2X/8/81dfa194f06cf3ec7ec9d0f578e9d6d0234f6966.jpeg)

What lines of code exactly do I add in to achieve this? I’m sorry if this seems like a very basic and stupid question, this is my very first processing assignment and programming has never been my forte… It would be much appreciated.

```auto
float center = 1;
float VenusOrbitRadius = 120;
float VenusAngle = 0;

void setup() {
  size(1024,768);
  
  frameRate(30);
}

void draw() {
  background(0,0,0);    
  translate(width/2,height/2);   
  noStroke();
  
  fill(255,200,64);             
  ellipse(0,0,center,center);  
    
  pushMatrix();
  
  rotate(VenusAngle);
  translate(VenusOrbitRadius,0);
  
  fill(255);
  ellipse(0,0,5,5);
  
  popMatrix();   
  VenusAngle += .05;  
}

```

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<div class="post-metadata">

**Author:** ![Kevin](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/kevin/32/2297_2.png) [@Kevin](https://discourse.processing.org/u/Kevin)\
**Post date:** [November 26, 2018, 9:09pm UTC](https://discourse.processing.org/t/how-to-add-a-trail-particle-effect-to-a-moving-circle/5967/2 "2018-11-26T21:09:30Z")

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Which part of this is giving you trouble?

The best advice I can give you is to [break your problem down into smaller steps](https://happycoding.io/tutorials/how-to/program) and take those steps on one at a time.

Can you get a single point rotating around the center? Can you give that point a trail?