Im really confused, i wrote/copied whatever,  this piece of code about 2 years ago and just came across it as it is perfect for some other idea am working on... its working but i just dont understand how...

this is the code :

Quote:


And ive got the following questions...

Why doesnt it work when i declare
float[] tmpX = new float[anzahl];
float[] tmpY = new float[anzahl];
outside of the draw function... its just declared there, why does it behave different when i do this outside the draw function?!

the next thing is, what the crappity smack am i doing here?

oldX=tmpX;
oldY=tmpY;

isnt it an array? what does it mean in this case? just a simple way for putting every single part of one array into another?


Why is there this Line going to the origin(0/0) at the beginning of the sketch? i mean i know there must be an array which is not filled and is still 0 but where is it?
its not:  oldX[i] = 0;oldY[i] = 0; ...

and last but not least...
How should i change my code so that the line stays the same when i dont move the mouse and only erases itself when i keep on moving...

WOW, im feeling stupid... this is for those people who love so solve Problems and reading code :) Thank you Guys!!

Thank you! but you are totally right, its getting really slow and the FPS drop (not in this example, the new one)

You would help me alot of you could maybe explain me how to reduce it and make it more efficent.

Thanks Philho!

int anzahl=29;
float[] linesX = new float[anzahl];
float[] linesY = new float[anzahl];

void setup(){
 size(400,400);
 background(255);
 frameRate(40);
}

void draw(){
background(255);

for(int i=anzahl - 2; i>=0; i--){
   linesX[i+1] = linesX[i];
   linesY[i+1] = linesY[i];
}
 
linesX[0]=mouseX;
linesY[0]=mouseY;

 for(int i=0; i<anzahl-1; i++){
   line(linesX[i],linesY[i],linesX[i+1],linesY[i+1]);
 }
}

all the copying of data in this strikes me as a bit wasteful. you could try a circular buffer instead which would get rid of the need of it. or, you guessed it, an ArrayList.

(ok, not really a problem with 29 values, but when you have 29,000...)

Like i said this was just an example i reused it for a different sketch with about 5.000-10.000 of these lines...
so im a bit confused now, 3 more ways to do that?

Code:

int queueSize = 50;

ArrayDeque lines;

void setup()
{
  size(700, 700);
  frameRate(40);
  lines = new ArrayDeque();
}

void draw()
{
  background(255);

  PVector p = new PVector(mouseX, mouseY);
  lines.addFirst(p);
  if (lines.size() > queueSize)
  {
    lines.removeLast();
  }

  Iterator it = lines.iterator();
  PVector pp = null;
  while (it.hasNext())
  {
    PVector cp = (PVector) it.next();
    if (pp != null)
    {
	line(pp.x, pp.y, cp.x, cp.y);
    }
    pp = cp;
  }
}
 

Yes, beyond the improvements to the syntax, Java 1.5 introduced a number of useful new classes.
Actually, even 1.4 had new stuff, I fear your copy of the book is badly outdated...
I have this book (probably the 1.4 edition) and I admit I rarely open it, going straight to the online JavaDoc!