Shooting stars along a random point ellipse

Paul00

Hi guys I'm new to processing so this is may be a silly questions for the mayority here : ).

I would like to be able to draw a series of shooting star that starts and ends to a random point of a stroke circle (for example an ellipse of 200 radius), not inside of it. I started by using a code of Charlie McDowell that I find on open processing, in wich creates exactly the same effect that I wanted to create, but the stars are randomly drawned on the size of the screen. How can I exactly set the start and end point of the star on random point of the ellipse perimeter?

Here is the code:

/* OpenProcessing Tweak of @http://www.openprocessing.org/sketch/41149@ / / !do not delete the line above, required for linking your tweak if you upload again / / This program draws a starry sky with stars that twinkle. It also includes randomly occuring shooting stars. Author: Charlie McDowell */

// // the tail of the shooting star int[] shootX = new int[30]; int[] shootY = new int[30]; int METEOR_SIZE = 10; // initial size when it first appears float meteorSize = METEOR_SIZE; // size as it fades

// distance a shooting star moves each frame - varies with each new shooting star float ssDeltaX, ssDeltaY; // -1 indicates no shooting star, this is used to fade out the star int ssTimer = -1; // starting point of a new shooting star, picked randomly int startX,startY;

void setup() { size(500,500); smooth(); }

void draw() { background(0); // dark blue night sky
//
// draw the shooting star (if any) for (int i = 0; i < shootX.length-1; i++) { int shooterSize = max(0,int(meteorSizei/shootX.length)); // to get the tail to disappear need to switch to noStroke when it gets to 0 if (shooterSize > 0) { strokeWeight(shooterSize); stroke(255); } else noStroke(); //line(shootX[i], shootY[i], shootX[i+1], shootY[i+1]); ellipse(shootX[i], shootY[i], meteorSizei/shootX.length,meteorSizei/shootX.length); } meteorSize=0.9; // shrink the shooting star as it fades
// move the shooting star along it's path for (int i = 0; i < shootX.length-1; i++) { shootX[i] = shootX[i+1]; shootY[i] = shootY[i+1]; }
// add the new points into the shooting star as long as it hasn't burnt out if (ssTimer >= 0 && ssTimer < shootX.length) { shootX[shootX.length-1] = int(startX + ssDeltaX(ssTimer)); shootY[shootY.length-1] = int(startY + ssDeltaY(ssTimer)); ssTimer++; if (ssTimer >= shootX.length) { ssTimer = -1; // end the shooting star

} }

// create a new shooting star with some random probability if (random(5) < 1 && ssTimer == -1) { newShootingStar();
} }

/* Starts a new shooting star by randomly picking start and end point. */ void newShootingStar() { int endX, endY; startX = (int)random(width); startY = (int)random(height); endX = (int)random(width); endY = (int)random(height); ssDeltaX = (endX - startX)/(float)(shootX.length); ssDeltaY = (endY - startY)/(float)(shootY.length); ssTimer = 0; // starts the timer which ends when it reaches shootX.length meteorSize = METEOR_SIZE; // by filling the array with the start point all lines will essentially form a point initialy for (int i = 0; i < shootX.length; i++) { shootX[i] = startX; shootY[i] = startY; } }

Thank you for your patience.

koogs

please format the code.

select it, hit ctrl-o.

Paul00

Hi koogs! Sorry about that, here is the code :

// the tail of the shooting star
int[] shootX = new int[50];
int[] shootY = new int[50];
int METEOR_SIZE = 10; // initial size when it first appears
float meteorSize = METEOR_SIZE; // size as it fades

// distance a shooting star moves each frame - varies with each new shooting star
float ssDeltaX, ssDeltaY; 
// -1 indicates no shooting star, this is used to fade out the star
int ssTimer = -1;
// starting point of a new shooting star, picked randomly
int startX,startY;


void setup() {
  size(500,500);
  smooth();
}

void draw() {
  background(0); // dark blue night sky

  //

  // draw the shooting star (if any)
  for (int i = 0; i < shootX.length-1; i++) {
    int shooterSize = max(0,int(meteorSize*i/shootX.length));
    // to get the tail to disappear need to switch to noStroke when it gets to 0
    if (shooterSize > 0) {
      strokeWeight(shooterSize);
      stroke(255);
    }
    else
      noStroke();
    line(shootX[i], shootY[i], shootX[i+1], shootY[i+1]);
    //ellipse(shootX[i], shootY[i], meteorSize*i/shootX.length,meteorSize*i/shootX.length);
  }
  meteorSize*=0.9; // shrink the shooting star as it fades

  // move the shooting star along it's path
  for (int i = 0; i < shootX.length-1; i++) {
    shootX[i] = shootX[i+1];
    shootY[i] = shootY[i+1];
  }

  // add the new points into the shooting star as long as it hasn't burnt out
  if (ssTimer >= 0 && ssTimer < shootX.length) {
    shootX[shootX.length-1] = int(startX + ssDeltaX*(ssTimer));
    shootY[shootY.length-1] = int(startY + ssDeltaY*(ssTimer));
    ssTimer++;
    if (ssTimer >= shootX.length) {
      ssTimer = -1; // end the shooting star


    }
  }

  // create a new shooting star with some random probability
  if (random(5) < 1 && ssTimer == -1) {
    newShootingStar();


  }
}

/*
  Starts a new shooting star by randomly picking start and end point.
*/
void newShootingStar() {
  int endX, endY;
  startX = (int)random(width);
  startY = (int)random(height);
  endX = (int)random(width);
  endY = (int)random(height);
  ssDeltaX = (endX - startX)/(float)(shootX.length);
  ssDeltaY = (endY - startY)/(float)(shootY.length);
  ssTimer = 0; // starts the timer which ends when it reaches shootX.length
  meteorSize = METEOR_SIZE;
  // by filling the array with the start point all lines will essentially form a point initialy
  for (int i = 0; i < shootX.length; i++) {
    shootX[i] = startX;
    shootY[i] = startY;
  }
}

TfGuy44

You should be able to use this example to accomplish what you want.

void setup(){
  size(600,600);
  background(0);
  noFill();
}

void draw(){
  stroke(random(255),random(255),random(255));
  translate(random(width),random(height));
  rotate(random(TWO_PI));

  //ellipse(0,0,random(200),random(200));

  float start = random(-TWO_PI,0);
  float len = random(TWO_PI);
  //arc(0,0,random(200),random(200),0,TWO_PI);

  arc(0,0,random(200),random(200),start,start+len);

}

Paul00

Thanks ttguy44! I'm almost getting there. Here is a new code that I rewrite.

float a = random(0.0, PI*2);
float speed = random (0.008, 0.02);

int startTime;
int counter = 1;
int number1;


void setup() {
  size(500, 500);
  background(0);
  smooth();
}

void draw() {

  fill (0, 50);
  noStroke();
  rect (0, 0, width, height); 
  fill(255);

  float x =  width /2 + cos (a) * 200;
  float y = height /2 + sin (a) * 200;

  fill(255);
  ellipse(x, y, 5, 5);
  a = a + speed;


  if (counter < 10) {
    if (millis() > startTime + 1000) {
      startTime = millis(); 
      noLoop();
      fill(0);
      rect (0, 0, width, height); 

    }
  }
}

I manage to get a shooting star (ellipse) appear in a random radians value along an ellipse of 200 pixel radius. But I'm quite stuck ... :( I don't know how to simply fade the ellipse after for ex 1 sec, without putting a black rectangle that covered brutaly the shape, and then generating new random star position without using predictable arrays. Any tips? Thank you again!

Chrisir

you can use fill with a 2nd parameter for opacity

over time decrease this value (as a var) from 255 to 0 I think

Paul00

Thanks Chrisir! I find another trick by decrasing the width and height of the ellipse, but now I don't really undestand how can repeate this infinetly times. I know that is the basics, please a little hint?

here is the code:

float a = random(0.0, PI*2);
float speed = random (0.00, 0.03);

float radius = 2;
float rMove = +1;
float minRadius = 1, maxRadius = 10;

int startTime;
int counter = 1;


void setup() {
  size(500, 500);
 // background(0);
  smooth();
}

void draw() {

  fill (0, 50);
  noStroke();
 rect (0, 0, width, height); 

  int r = 200;
  float x =  width /2 + cos (a) * r;
  float y = height /2 + sin (a) * r;
  a = a + speed;
  fill(255);

  ellipse(x, y, radius, radius);
  radius += rMove; 
  if (radius > maxRadius)
    rMove = -1;
  else if (radius < minRadius)
    rMove =0.0;
}

Thank you :)

Chrisir

last line:::::: rMove = 1.0;

Paul00

I'm sorry I do not explained very well : /. I would like to create another ellipse with the same random radians probability of the first one. Having a star shooting one after another one. loooooooping over and over :D

Chrisir

do you see only one ellipse at a time or many?

Chrisir

when it's only one at a time: how long is it there? 360° ?

Paul00

I see 1 ellipse at the time. The x and y of the ellipse are set to the width and height /2 + cos (a) * r (wich is 200 ); and (a) is a random value of (0.0, PI*2); and also the speed is a random value. So each time I run the sketch is a different type of shooting star wich is exactly what I want. But I would like to have that over and over without pressing play each time. This sound reeeally bad I know sorry, I 'm just new to it so I would like to undestand it better. Thank you Chrisir! :)

Chrisir

puuuh

ok, a is the angle, when a is > TWO_PI we want to start all over

since you set all vars before setup() when declaring them, I advice you to

have before setup() only float a; etc. etc.

then have a new function reset where you saya = random(0.0, PI*2); etc. etc.

without the float !!!!

now call reset from setup() and when a is > TWO_PI

Paul00

yeeeeesss! It is working now, thank you so much Chrisir! :)

Chrisir

great!