/**
* a gear demo by <a href="http://www.local-guru.net/blog">Guru</a>
*/

void setup() {
  size(300,300);
  smooth();
  frameRate(25);
}

float a = 0;

void draw() {
  background(255);  
  a += 0.05;
  strokeWeight( 2 );
  
  fill(255,0,0);   
  pushMatrix();
  translate( width/2, height/2 );
  rotate( a );
  gear( 8, 40, 50, PI/32 );
  popMatrix();

  fill(255,255,0);   
  pushMatrix();
  translate( width/2, height/2-90 );
  rotate( -a );
  gear( 8, 40, 50, PI/32 );
  popMatrix();
  
  fill(0,0,255);   
  pushMatrix();
  translate( width/2+90, height/2 );
  rotate( -a );
  gear( 8, 40, 50, PI/32 );
  popMatrix();
  
  fill(0,255,0);   
  pushMatrix();
  translate( width/2-64, height/2+64 );
  rotate( -a );
  gear( 8, 40, 50, PI/32 );
  popMatrix();

}

void gear( int tooth, int ri, int ro, float o ) {
  beginShape();
  for( int i = 0; i < tooth; i++ ) {
    vertex(cos(2*PI/tooth * i - o ) * ri, sin(2*PI/tooth*i - o) * ri);
    vertex(cos(2*PI/tooth * i + o ) * ro, sin(2*PI/tooth*i + o) * ro); 
    vertex(cos(2*PI/(2*tooth) * (2*i+1) - o) * ro, sin(2*PI/(2*tooth)*(2*i+1) - o) * ro); 
    vertex(cos(2*PI/(2*tooth) * (i*2+1) + o) * ri, sin(2*PI/(2*tooth)*(2*i+1) + o) * ri);  
  }
  endShape(CLOSE);
}