/*

   File lighting.c

   Contains the functions involved with lighting the scene
   currently compile with -opt 4

   Phil Atkin

   (c) Division Ltd. 1991, 1992

   Modifications
   16th Dec 1992 new Phong shader, requires &H vector in bulb->xformpos[3]



*/

#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include "dpltypes.h"
#include "macros.h"
#include "speclght.h"

/*{{{  #define dot(d,a,b)*/
#define dot(d,a,b)                \
ax=*a++; bx=*b++; ay=*a++; by=*b++; az=*a++; bz=*b++;  \
d=((ax*bx)+(ay*by)+(az*bz))
/*}}}  */
/*{{{  #define sdot(d,a,b)*/
#define sdot(d,a,b,cook)                               \
ax=*a++; bx=*b++; ay=*a++; by=*b++; az=*a++; bz=*b++;  \
d=cook*((ax*bx)+(ay*by)+(az*bz))
/*}}}  */


/*{{{  void traceLights ( dpl_LMODEL *head )*/
void traceLights ( dpl_LMODEL *head )
{
  dpl_list *list=head->light_list;

  printf ("Trace_lights\n" );

  while (list) {
    dpl_LIGHT *l=(dpl_LIGHT *) list->item;

    printf ("Bulb 0x%x type 0x%x pos %f,%f,%f\n",
       (int) head, head->positional,
         head->position[0],
         head->position[1],
         head->position[2] );
    list=list->next;
  }
}
/*}}}  */

/*{{{  void reorderLights ( LIGHTSOURCE *head )*/
void reorderLights ( LIGHTSOURCE **head )
{
  /*
    this function places all ambient lights at the head of the list,
    and returns a pointer to the last non-ambient source
  */
  LIGHTSOURCE *ambient_head=NULL,
              *direct_head=NULL,
              *prev=NULL,
              *bulb=*head,
              *ambient_tail=NULL;

  /*{{{  traverse list, put bad or disabled lights into ambient list (hack!)*/
  
  while (bulb) {
    LIGHTSOURCE *next=bulb->next;
    float hyp, one=1.0f, px, py, pz;
    int bogus=0;
  
    px=one*bulb->position[0];
    py=one*bulb->position[1];
    pz=one*bulb->position[2];
  
    hyp=(px*px) + (py*py) + (pz*pz);
  
    if (hyp < 0.01f)
      bogus=1;
    if (bulb->positional == light_null)
      bogus=1;
  
    /* note that prev is the last bulb we left in the lights list */
    if (bogus || (bulb->positional == light_ambient)) {
      /*{{{  chain out, in*/
      LIGHTSOURCE *next=bulb->next;
      
      /* chain this bulb into ambient list */
      
      if (ambient_head==NULL) {
        ambient_tail=bulb;
      }
      
      bulb->next=ambient_head;
      ambient_head=bulb;
      
      /* chain this bulb out of lights list */
      
      if (prev == NULL)
        *head=next;
      else
        prev->next=next;
      /*}}}  */
    }
    else
      prev=bulb;
  
    bulb=next;
  }
  /*}}}  */

  direct_head=*head;

  /*{{{  merge lists, with ambient at head*/
  
  if (ambient_tail != NULL) {
    ambient_tail->next=*head;
    *head=ambient_head;
  }
  /*}}}  */


  return direct_head;
}
/*}}}  */
/*{{{  int keep_this_bulb ( LIGHTSOURCE *bulb, MATRIX m, POINT p )*/
int keep_this_bulb ( LIGHTSOURCE *bulb, POINT centroid, POINT p )
{
  if (bulb->positional == light_directional) {
    p[0]=bulb->position[0];
    p[1]=bulb->position[1];
    p[2]=bulb->position[2];
    p[3]=1.0f;

    return 1;
  }
  else if (bulb->positional == light_positional) {
    float r, ir;
    float dx, dy, dz;

    dx=centroid[0]-bulb->position[0];
    dy=centroid[1]-bulb->position[1];
    dz=centroid[2]-bulb->position[2];

    r  = sqrt((dx*dx) + (dy*dy) + (dz*dz));
    ir = 1.0f/r;

    if (r > bulb->max_rad)
      return 0;
    else {
      if (r < bulb->min_rad)
        p[3]=1.0f;
      else
        p[3]=1.0f - ((r - bulb->min_rad) / (bulb->max_rad - bulb->min_rad));

      p[0]=-dx*ir;
      p[1]=-dy*ir;  /* i think this is due to the -1 in the matrix */
      p[2]=-dz*ir;

      return 1;
    }
  }
  else
    return 0;
}
/*}}}  */