Processing 1.0 - Processing Discourse - Unknown Number of Particles

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Unknown Number of Particles (Read 1037 times)

Kevin

Unknown Number of Particles
Dec 31^st, 2005, 6:52pm

Hi,

I'm creating an example of rain. As such I have a number of 'taps' which drip a droplet of rain. The dripRate can be changed on the fly.

I've been looking at examples as much as possible, but everything seems to have a predefined number of drops, and that's confusing me.

I'm used to Actionscript, where I can just create an object and let it fall and delete itself. I think that mindset is causing me trouble though.

Can anyone point me to a good example?

Thanks,

seltar

Re: Unknown Number of Particles
Reply #1 - Jan 1^st, 2006, 4:12pm

Just something i whipped up for you...
It can add as many particles as you like, but it runs through all the particles (and skips drawing the ones outside the screen)..

Press space to add a droplet..

Code:


// Dynamic Rain - Simple

float speed = 0.61;
RainSystem t;

void setup()
{
  size(200,200);
  smooth();
  t = new RainSystem();
}

void draw()
{
  background(0);
  t.draw();
}

class Drop
{
  float x, y;
  boolean alive;
  Drop(float X, float Y)
  {
    alive = true;
    x = X;
    y = Y;
  }
  
  void update()
  {
    y += speed;
    if(x < 0 || x >= width || y < 0 || y >= height) alive = false;
  }
  
  void draw()
  {
    update();
    noStroke();
    fill(255);
    ellipse(x,y,2,5);
  }
}

class RainSystem
{
  int n = 0;
  Drop[] drops;
  RainSystem()
  {
    drops = new Drop[n];
    addDrop(random(width),0);
  }
  
  void addDrop(float X, float Y)
  {
    Drop[] tmp = new Drop[n+1];
    arraycopy(drops,0,tmp,0,n);
    drops = tmp;
    drops[n++] = new Drop(X,Y);
  }
  
  void draw()
  {
    for(int i = 0; i < drops.length; i++)
	if(drops[i].alive) drops[i].draw();
  }
}

void keyPressed()
{
  if(key==' ') t.addDrop(random(width-1),0);
}

-seltar

I'm bored, therefore I program
http://seltar.org > seltar's special place
http://snippet.seltar.org > seltar's snippet palace
http://libraries.seltar.org > seltar's libraries

mflux

Re: Unknown Number of Particles
Reply #2 - Jan 3^rd, 2006, 5:14am

You can also use Vector documented at
http://java.sun.com/j2se/1.4.2/docs/api/java/util/Vector.html

For example...

Vector list;
list = Vector();

//list is now a dynamic array. Technically it is a linked list.

list.add(myObject);

//now list.get(0) will return myObject, but you need to cast it...

myObjectType temp = (myObjectType) list.get(0);

You can .add() as many as you want, or remove, etc.

Portfolio

scloopy Junior Member Offline Posts: 74	Re: Unknown Number of Particles Reply #3 - Jan 3^rd, 2006, 11:36pm Sometimes it's easier to convert the whole Vector to an array if you're going to be looping through it over and over (and it doesn't change) You can do it like this: Code: myObjectType arr[] = new myObjectType[list.size()]; list.toArray(arr); for(int i=arr.length; --i>=0;) // do something with arr[i] hth

fry YaBB Moderator Offline Posts: 2623 mass, usa	Re: Unknown Number of Particles Reply #4 - Jan 4^th, 2006, 6:34pm arrays will also be much faster than vectors (usually 2x), especially when used heavily in draw() or that sort of thing.

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