/* posmod.c

   Position modulation code

   Copyright (c) 1998-1999, Mike Oliphant and Rob Clark
*/

#include "math.h"
#ifdef __EMX__ /*os2*/
  #include "float.h"
#endif
#include "pyro.h"


/* Normal behavior until dx and dy slow down, then increase air resistance */

void xz_wobble(Particle *part,Firework *work)
{

  double t;
  double sp=0.05; /* + = faster */
  double wfact=0.05;

  if(part->expvel==0.0 || (fabs(part->dx)<0.001 && fabs(part->dz)<0.001)) {
	if(part->expvel!=0.0) {  /* need to mark a flag in the particle */
	  part->expvel=0.0;      /* this will do as it is not need any longer */
	  part->airres-=0.01;    /* and =! 0.0 under normal circumstances. */
	}
	
	t=sp*(work->timer*(3*part->rval+1)+part->rval*2*M_PI);
	part->mx=part->x+wfact*sin(t);
	part->my=part->y;
	part->mz=part->z+wfact*cos(t);
  }
  else {
	  part->mx=part->x;
	  part->my=part->y;
	  part->mz=part->z;
  }
}