i am using traer physics to create some kind of creatures and i want to keep the structure as simple as possible. so creating some meshes is maybe not a god solution. Anyway. What i want to do is to add images to the particles. But i am having some problems rotating the images they way they should be.
To explain it better i made a quick sketch of what i got and what i want.



I know i asked some similar questions before. But is there a simple way to do that without adding any more particles or do some complicated vector math?


Here is some code to test it :

Code:

import traer.physics.*;

Particle mouse, p1, p2;
Particle[] ball;
Spring[] s;
ParticleSystem physics;



void setup(){
  size( 400, 400 );
  frameRate( 24 );
  smooth();
  ellipseMode( CENTER );
  noStroke();

  //Create ParticleSystem
  physics = new ParticleSystem( 0, 0.1 );

  //Create Particles
  mouse = physics.makeParticle();
  mouse.makeFixed();

  ball = new Particle[10];
  s = new Spring[10];

  //Mouse Attraction
  for(int i=0; i<  ball.length; i++){
    ball[i] = physics.makeParticle( 1.0, random( 0, width ), random( 0, height ), 0 );
    physics.makeAttraction( mouse, ball[i],  3000, 50 ); 
  }

  for(int i=0; i<  ball.length; i++){ 
    for(int j=i+1; j<  ball.length; j++){ 
	physics.makeAttraction( ball[i], ball[j], -4000, 50 );
    }
  }

  //Create Springs with strength, damping,  restLength
  for(int i=0; i<  ball.length-1; i++){ 
    s[i] = physics.makeSpring( ball[i], ball[i+1], 0.5, 0.1, 10);
  }
  s[9] = physics.makeSpring( ball[0], ball[ball.length-1], 0.5, 0.1, 10);


}


void draw(){

  mouse.position().set( mouseX, mouseY, 0 );
  physics.tick();

  background( 255 );
  fill(0);
  ellipse(mouse.position().x(),mouse.position().y(),15,15);

  for ( int i = 0; i < ball.length; i++ )
  {
    beginShape();
    fill(255,0,0,150);
    rect(ball[i].position().x(),ball[i].position().y(),2,25);
    //   ellipse(ball[i].position().x(),ball[i].position().y(),5,5);
  }



  stroke(0);

  for(int i=0; i<  ball.length-1; i++){ 
    line( ball[i].position().x(), ball[i].position().y(), ball[i+1].position().x(), ball[i+1].position().y() );
  } 
  line( ball[0].position().x(), ball[0].position().y(), ball[ball.length -1].position().x(), ball[ball.length -1].position().y() );

  noStroke();
} 

Thats really good. Thank you!
i had a similar idea when i was on the bust today.
i thought i could use the coordinates of the points to get the rotating angle. thast actually really close to what you suggested...

i used your code and just adapted it to what i thought of...

  Code:

for ( int i = 0; i < ball.length; i++ )  {
    
  float x1 = ball[i].position().x();
  float y1 = ball[i].position().y();
  float x2 = ball[i+1].position().x();
  float y2 = ball[i+1].position().y();
 
float a = atan2(y2 - y1, x2 - x1);
  pushMatrix();
    translate(x1 + (x2 - x1)/2, y1 + (y2 - y1)/2);
    rotate(a);
    rect(0, 0, 2, 25);
  popMatrix();
  } 

its working rightnow.

only problem i dont know how to align the last or first element and draw it within the for loop.

oh and another question is, do you know what to change to get them pack to the particle positions (corners of the shape) and not between them ?


here is the whole working code :
Code:

import traer.physics.*;

Particle mouse, p1, p2;
Particle[] ball;
Spring[] s;
ParticleSystem physics;



void setup(){
  size( 400, 400 );
  frameRate( 24 );
  smooth();
  ellipseMode( CENTER );
  noStroke();
 
  //Create ParticleSystem
  physics = new ParticleSystem( 0, 0.1 );

  //Create Particles
  mouse = physics.makeParticle();
  mouse.makeFixed();

  ball = new Particle[10];
  s = new Spring[10];

  //Mouse Attraction
  for(int i=0; i<  ball.length; i++){
    ball[i] = physics.makeParticle( 1.0, random( 0, width ), random( 0, height ), 0 );
    physics.makeAttraction( mouse, ball[i],  3000, 50 ); 
  }

  for(int i=0; i<  ball.length; i++){ 
    for(int j=i+1; j<  ball.length; j++){ 
	physics.makeAttraction( ball[i], ball[j], -4000, 50 );
    }
  }

  //Create Springs with strength, damping,  restLength
  for(int i=0; i<  ball.length-1; i++){ 
    s[i] = physics.makeSpring( ball[i], ball[i+1], 0.5, 0.1, 10);
  }
  s[9] = physics.makeSpring( ball[0], ball[ball.length-1], 0.5, 0.1, 10);


}


void draw(){

  mouse.position().set( mouseX, mouseY, 0 );
  physics.tick();

  background( 255 );
  fill(0);
  ellipse(mouse.position().x(),mouse.position().y(),15,15);

  

 
  for ( int i = 0; i < ball.length-1; i++ )  {
    
  float x1 = ball[i].position().x();
  float y1 = ball[i].position().y();
  float x2 = ball[i+1].position().x();
  float y2 = ball[i+1].position().y();
 
float a = atan2(y2 - y1, x2 - x1);
  pushMatrix();
    translate(x1 + (x2 - x1)/2, y1 + (y2 - y1)/2);
    rotate(a);
    rect(0, 0, 2, 25);
  popMatrix();
  }



  stroke(0);

  for(int i=0; i<  ball.length-1; i++){ 
    line( ball[i].position().x(), ball[i].position().y(), ball[i+1].position().x(), ball[i+1].position().y() );
  } 
  line( ball[0].position().x(), ball[0].position().y(), ball[ball.length -1].position().x(), ball[ball.length -1].position().y() );

  noStroke();
} 



 

alright, i will try and work with the springs. probably the better solution in this case! thx again