Hi, I am brand new to processing, and got the blue processing book, very good by the way.

My question is can you show me how can I do a rotation with easing?

I try the formulas on the book, ease, how to do use rotate, radinas and all that but I cant work out how can I apply the ease formula to a rotation or angular movement

Thanks!
rS

I know this is a very old thread but instead of starting a new one I'll ask this question on the same subject:

I ease my angle and it works fine until the target angle suddenly goes from -pi to +pi. I know why this happens, the target pass the x-axis of the aimer, on the left side on the y-axis. The thing that is easing will make a sudden jump almost 2 pi in one direction.

I guess the problem could be solved by keeping previous direction values and compare them to the new ones, but is there an easier way to avoid this "spin" that appears?

thanks
h

Yes I am. I'll make an example of my code where I aim for the mouse:

Code:

float goalDirection;
float currentDirection;
float easeValue = 20;

void setup(){
  size(400,400);
}
void draw(){
  background(200);
  goalDirection = atan2(mouseY - height/2, mouseX - width/2);
  currentDirection += (goalDirection - currentDirection) / easeValue;
  pushMatrix();
  translate(width/2,height/2);
  line(-width/2,0,0,0);
  rotate(currentDirection);
  line(0,0,width/2,0);
  popMatrix();
}
void mousePressed(){
  println("The goalDirection: "+goalDirection+"\t The difference with easing: "+(goalDirection-currentDirection)/easeValue);
} 

Excuse me for the long piece of code. If you click once above and once below the line you will print the goalDirection and see that it will jump from ≈-pi to ≈+pi. This makes my "aimer" jump one lap instead on pass over the line. Mathematical this is not strange at all but I need a work around.

I hope you understand my problem, thanks for helping!
h

PhiLho  wrote on Jul 30^th, 2009, 1:17pm:


Indeed! At first I thought it must have been lost somewhere when posted, but then realised hampus must be a master of understatement

Glad you had a solution to this one - though I imagine it must be something that crops up a lot when rotating.  I thought it might help to add TWO_PI so all values were positive, but hadn't got beyond that.

hampus wrote on Jul 30^th, 2009, 6:43pm:


Just remember that you can only have a single 'doThis' statement if you neglect the {braces}.

I don't especially like missing out the braces; nor when people start their opening braces on the next line from the condition... But I guess it all comes down to personal coding style and preferences.  The important thing is to be consistent

Either that or use Python  

Yeah I started using it and changed some of my code but it turns out to be harder to read. And, as you said, braces at new lines is confusing aswell. I'll keep it the easy way, except for this:

I managed to solve the final problem with the easing. I added a print and saw that the temporary angel became odd things such as ≈9.123 and other odd numbers above 2 pi / beneath -2 pi, so I made this:

Code:

while(temporaryDirection < -PI) temporaryDirection += TWO_PI;
while(temporaryDirection > PI) temporaryDirection -= TWO_PI; 

This way the temporary angel will always be inside the gap from -pi to +pi and always run the direction that you want. (I think, as I tried for some laps forth and back. But as usual things tend to change and do exactly what you don't want them too, so I don't promise anything, haha, don't want to risk lying.)
h