so i have a object that's rotating, based on it's position and the mouse so it would face the mouse, i'm using atan2 but when you position the mouse directly behind the object, horizontally, it bounces the other way instead of just following through.  i know this is a simple solution, but i can't think of any right now.  help?



Fish fishies [];
void setup(){
size(400,400);
fishies=new Fish[9];
for(int i=0; i<9; i++){
 fishies[i]=new Fish(i);
}
framerate(30);
noStroke();
}
void draw(){
background(0);
 for(int i=0; i<9; i++){
 fishies[i].move();
   fishies[i].draw();
 }
}
class Fish
{
 float x,y,r,xv,yv,xa,ya,xd,yd;
 int i;
 int d;
 Fish(int i){
 this.i=i;
 this.x=30+(i*10);
 this.y=100;
 this.r=0;
 }
 void move(){

 if(i==0){
 
 if(mouseY!=0){
   r+=((atan2(mouseY-y,mouseX-x))-r)/10;
   
   println(degrees(r));
   }
 if(i!=0){
 if(dist(fishies[i-1].x,fishies[i-1].y,this.x, this.y)<5){
     
}
}
}
void draw(){
pushMatrix();
 translate(x,y);
 pushMatrix();
 rotate(r);
 rect(0,0,10,20);
 popMatrix();
 popMatrix();
 }
   
   }

Came up with a solution to your problem last night, as I had always had this problem myself.

Already IMed it to you, but I'll post the solution here to share with everyone.

Jay. You owe me a cute japanese girl or three beers.



Solution:
http://users.design.ucla.edu/~mflux/p5/angexample/

That's pretty much it. It allows you to keep adding angles as you rotate, dialing upwards or downwards into the negative. This way it keeps your numbers on a scale rather than wrap between 0 and 360.

The following code does the trick:

Code:

  mousePos=new vec(mouseX,mouseY);	
  float angDiff=getAng(center,mousePos)-ang;
  ang=getAng(center,mousePos);
  
  if(angDiff>180)
  {
    angDiff=angDiff-360;
  }
  if(angDiff<-180)
  {
    angDiff=angDiff+360;  
  }
  totalAng+=angDiff;

 

totalAng will give you the final value.