Modify a text file: $/orbit/orbit2.java

$/orbit/orbit2.java

//////// Planets orbit the sun.  (bam/CST112) ////////

Planet[] p;
int np=0;
int line=0;
float textX=10,textY=10;

float GM=100;

float theta=0;    // Angle from sun to planet.
float sunX=  width/2;
float sunY=  height/2;
float sunR=  80;

color[] colorlist= { 
  color(150,150,150), 
  color(200,255,200), 
  color(150,200,250), 
  color(255,200,200), 
  color(255,127,200), 
  color(200,200,150), 
  color(100,100,200), 
  color(127,200,100) 
};
String[] namelist= { "Mercury", "Venus", "Terra", "Mars", "Jupiter", "Saturn", "Uranus", "Neptune" };

boolean debug=false;  
boolean lines=true;

void setup() {
  size(800,800);
  theta=0;    // Angle from sun to planet.
  sunX=  width/2;
  sunY=  height/2;
  sunR=  40;

p=  new Planet[100];

for( int i=0; i<np; i++) {
    p[i]=  new Planet(random( 500 ) );
  }
  
  //// Create the eight planets.

}

void draw() {
  background ( 255 );
  //  background( 0 );

line=0;
  fill(0);
  text( np+" planets", width-100, 20 );
  
  sun();
  
  // Planets.
  for( int i=0; i<np; i++) {
    p[i].move();
    p[i].show();
  }
}

void sun() {
  //// Draw the sun;
  fill( 255,255,0);
  ellipseMode(RADIUS);
  ellipse( sunX, sunY, sunR, sunR );
}
void nextline( String s ) {
  //// Display text on next available line.
  text( s, textX, textY+15*line++ );
}

void mousePressed() {
  //// Check for click on a planet.
  //// Drag it to an orbital position and recalculate velocity.
  fill(0);
  float r=  dist(mouseX,mouseY, sunX,sunY);
  nextline( mouseX+", "+mouseY );
  p[np]=  new Planet( r );
  p[np].c=  np<colorlist.length ? colorlist[np] : color( random(255), random(255), random(255) );
  if (np<namelist.length) p[np].name=  namelist[np];
  p[np].pR=  2+random(10);
  np++;
}

void keyPressed() {
  //// Check which key.
  if (key == 'd') debug=  ! debug;    // Toggle debugging flag.
  if (key == 'l') lines=  ! lines;    // Toggle lines flag.
}

class Planet
{
  //// Planet date and orbit data.
  
  // ORBIT:
  float r= 150;      // Radius of the orbit.  (~ 150 M km )
  float d = PI * 2 * r;    // Distance travelled in one period.
  float t = 365*24*60*60;  // Time to complete the orbit  (year)
  float v= d / t;          // Velocity of planet.
  
  float dtheta=  0.01;
  
  // POSITION & VELOCITY of the planet:
  float theta=0;    // Angle from sun to planet.
  //float x=sunX, y=sunY-r;
  float x= sunX;
  float y= sunY - r;
  float dx= v * sin(theta);
  float dy= v * cos(theta);

// PLANET details:
  float pR=  6;          // Radius of planet.
  color c=  color(200,255,255);
  color cNite=  color(100,100,100);  
  String name="Whateveer" ;

// CONSTRUCTORS //
  Planet() {}
  Planet( float rset ) {
    //// Set planetary radius.
    r=  rset;
    v=  sqrt( GM / r );
    if (np<colorlist.length)  c=  colorlist[np];
    else c=  color( random(255), random(255), random(255) );
    //// create planet where mouse is!
    x=  mouseX;
    y=  mouseY;
    theta=  atan( (mouseX-sunX) / (mouseY-sunY) );
  }

// METHODS //
  void move() {
    //// Move in circular orbit
    x += v * cos(theta);
    y += v * sin(theta);
    theta += dtheta;
  }
  
  void show() {
    //// Show the planet at new position (x,y)
    fill( c );
    ellipseMode( RADIUS );
    ellipse( x, y, pR, pR );
    text( name, x+pR+20, y );
    // Debugging:  coords
    if (debug) {
      text( x+", "+y, x+40, y+15);
    }
    // Lines
    if (lines) {      line(sunX,sunY, x,y );    }
  }

}