// Hilfsfunktion: setzt den Vektor auf Zufallsrichtung und -Länge
function vec_randomize(&vec,range)
{
  vec[0] = random(1) - 0.5;
  vec[1] = random(1) - 0.5;
  vec[2] = random(1) - 0.5;
  vec_normalize(vec,random(range));
} 		

// Hilfsfunktion: blendet einen Partikel aus
function part_alphafade()
{
  my.alpha -= time+time;
  if (my.alpha <= 0) { my.lifespan = 0; } // Alpha <= 0, dann Partikel vernichten
}

//Partikelfunktion: generiert eine verblassende Explosion in Richtung vel 
function effect_explo()
{
  vec_randomize(temp,10);
  vec_add(my.vel_x,temp);
  my.alpha = 25 + random(25);
  my.bmap = scatter_map;
  my.flare = on;
  my.bright = on;
  my.beam = on; //Partikel verschmieren
  my.move = on;
  my.function = part_alphafade; // ändere in eine kürzere, schnellerer Funktion
}
...
vec_scale(normal,10); // produziere eine Explosion in Richtung der Normalen
effect(effect_explo,1000,my.x,normal);

function eff_somerandomeffect(PARTICLE* p) {
	vec_add(p.x,vector(random(4)-2,0,random(4)-2));
	vec_add(p.vel_x,vector(random(2)-1,0,random(2)-1));
	set(p, MOVE | BRIGHT | BEAM);
	p.bmap = bmp_flame_circle32;
	p.alpha = 60+random(40);
	p.size = 16+random(4);
	p.event = eff_fadefunction;
}

function p_alphafade(PARTICLE *p)
{
    p.alpha -= p.skill_a*time_step;
    if (p.alpha <= 0) p.lifespan = 0;
}

function p_trace(PARTICLE *p)
{
   set(p, BRIGHT|TRANSLUCENT|BEAM);
   p.size = 2;
   p.skill_a = 1; // fade factor
   p.event = p_alphafade;
}

// entity that runs in circles and leaves a vapor trail
action tracer()
{
   var dist = 0,radius = 10,sign = 1;
   VECTOR last_pos;
   while(1) 
   {
      vec_set(last_pos,my.x);
      dist += 30*time_step;
      radius += sign*random(3)*time_step; // change radius randomly
      if (radius > 150) sign = -1;
      else if (radius < 30) sign = 1;
      my.x = radius*sin(dist);
      my.y = radius*cos(dist);
      effect(p_trace,1,my.x,vec_sub(last_pos,my.x));
      wait(1);
   }
}

function main()
{
  vec_set(sky_color,vector(50,1,1)); // dark blue
  level_load(NULL);
  video_window(NULL,NULL,0,"Vapor trail demo");
  vec_set(camera.x,vector(-250,0,50));
  vec_set(camera.pan,vector(0,-15,0));

  ent_create(NULL,vector(0,0,0),tracer);  
}