text: #ifndef lint
  static const char	RCSid[] = "$Id: srcdraw.c,v 2.16 2005/04/19 01:15:07 greg Exp $";
  #endif
  /*
   * Draw small sources into image in case we missed them.
   *
   *  External symbols declared in ray.h
   */
  
  #include "copyright.h"
  
  #include  "ray.h"
  #include  "view.h"
  #include  "otypes.h"
  #include  "source.h"
  
  
  #define	CLIP_ABOVE	1
  #define CLIP_BELOW	2
  #define CLIP_RIGHT	3
  #define CLIP_LEFT	4
  
  #define MAXVERT		10
  
  typedef struct splist {
  	struct splist	*next;			/* next source in list */
  	int	sn;				/* source number */
  	short	nv;				/* number of vertices */
  	RREAL	vl[3][2];			/* vertex array (last) */
  } SPLIST;				/* source polygon list */
  
  extern VIEW	ourview;		/* our view parameters */
  extern int	hres, vres;		/* our image resolution */
  static SPLIST	*sphead = NULL;		/* our list of source polys */
  
  static int inregion(RREAL p[2], double cv, int crit);
  static void clipregion(RREAL a[2], RREAL b[2], double cv, int crit, RREAL r[2]);
  static int hp_clip_poly(RREAL vl[][2], int nv, double cv, int crit,
  		RREAL vlo[][2]);
  static int box_clip_poly(RREAL vl[MAXVERT][2], int nv,
  		double xl, double xr, double yb, double ya, RREAL vlo[MAXVERT][2]);
  static double minw2(RREAL vl[][2], int nv, double ar2);
  static void convex_center(RREAL vl[][2], int nv, RREAL cv[2]);
  static double poly_area(RREAL vl[][2], int nv);
  static int convex_hull(RREAL vl[][2], int nv, RREAL vlo[][2]);
  static void spinsert(int sn, RREAL vl[][2], int nv);
  static int sourcepoly(int sn, RREAL sp[MAXVERT][2]);
  
  
  static int
  inregion(			/* check if vertex is in region */
  	RREAL	p[2],
  	double	cv,
  	int	crit
  )
  {
  	switch (crit) {
  	case CLIP_ABOVE:
  		return(p[1] < cv);
  	case CLIP_BELOW:
  		return(p[1] >= cv);
  	case CLIP_RIGHT:
  		return(p[0] < cv);
  	case CLIP_LEFT:
  		return(p[0] >= cv);
  	}
  	return(-1);
  }
  
  
  static void
  clipregion(		/* find intersection with boundary */
  	register RREAL	a[2],
  	register RREAL	b[2],
  	double	cv,
  	int	crit,
  	RREAL	r[2]	/* return value */
  )
  {
  	switch (crit) {
  	case CLIP_ABOVE:
  	case CLIP_BELOW:
  		r[1] = cv;
  		r[0] = a[0] + (cv-a[1])/(b[1]-a[1])*(b[0]-a[0]);
  		return;
  	case CLIP_RIGHT:
  	case CLIP_LEFT:
  		r[0] = cv;
  		r[1] = a[1] + (cv-a[0])/(b[0]-a[0])*(b[1]-a[1]);
  		return;
  	}
  }
  
  
  static int
  hp_clip_poly(	/* clip polygon to half-plane */
  	RREAL	vl[][2],
  	int	nv,
  	double	cv,
  	int	crit,
  	RREAL	vlo[][2]	/* return value */
  )
  {
  	RREAL	*s, *p;
  	register int	j, nvo;
  
  	s = vl[nv-1];
  	nvo = 0;
  	for (j = 0; j < nv; j++) {
  		p = vl[j];
  		if (inregion(p, cv, crit)) {
  			if (!inregion(s, cv, crit))
  				clipregion(s, p, cv, crit, vlo[nvo++]);
  			vlo[nvo][0] = p[0]; vlo[nvo++][1] = p[1];
  		} else if (inregion(s, cv, crit))
  			clipregion(s, p, cv, crit, vlo[nvo++]);
  		s = p;
  	}
  	return(nvo);
  }
  
  
  static int
  box_clip_poly(	/* clip polygon to box */
  	RREAL	vl[MAXVERT][2],
  	int	nv,
  	double	xl,
  	double	xr,
  	double	yb,
  	double	ya,
  	RREAL	vlo[MAXVERT][2]	/* return value */
  )
  {
  	RREAL	vlt[MAXVERT][2];
  	int	nvt, nvo;
  
  	nvt = hp_clip_poly(vl, nv, yb, CLIP_BELOW, vlt);
  	nvo = hp_clip_poly(vlt, nvt, ya, CLIP_ABOVE, vlo);
  	nvt = hp_clip_poly(vlo, nvo, xl, CLIP_LEFT, vlt);
  	nvo = hp_clip_poly(vlt, nvt, xr, CLIP_RIGHT, vlo);
  
  	return(nvo);
  }
  
  
  static double
  minw2(			/* compute square of minimum width */
  	RREAL	vl[][2],
  	int	nv,
  	double	ar2
  )
  {
  	double	d2, w2, w2min, w2max;
  	register RREAL	*p0, *p1, *p2;
  	int	i, j;
  				/* find minimum for all widths */
  	w2min = FHUGE;
  	p0 = vl[nv-1];
  	for (i = 0; i < nv; i++) {	/* for each edge */
  		p1 = vl[i];
  		d2 = (p1[0]-p0[0])*(p1[0]-p0[0]) +
  				(p1[1]-p0[1])*(p1[1]-p0[1])*ar2;
  		w2max = 0.;		/* find maximum for this side */
  		for (j = 1; j < nv-1; j++) {
  			p2 = vl[(i+j)%nv];
  			w2 = (p1[0]-p0[0])*(p2[1]-p0[1]) -
  					(p1[1]-p0[1])*(p2[0]-p0[0]);
  			w2 = w2*w2*ar2/d2;	/* triangle height squared */
  			if (w2 > w2max)
  				w2max = w2;
  		}
  		if (w2max < w2min)	/* global min. based on local max.'s */
  			w2min = w2max;
  		p0 = p1;
  	}
  	return(w2min);
  }
  
  
  static void
  convex_center(		/* compute center of convex polygon */
  	register RREAL	vl[][2],
  	int	nv,
  	RREAL	cv[2]		/* return value */
  )
  {
  	register int	i;
  					/* simple average (suboptimal) */
  	cv[0] = cv[1] = 0.;
  	for (i = 0; i < nv; i++) {
  		cv[0] += vl[i][0];
  		cv[1] += vl[i][1];
  	}
  	cv[0] /= (double)nv;
  	cv[1] /= (double)nv;
  }
  
  
  static double
  poly_area(			/* compute area of polygon */
  	register RREAL	vl[][2],
  	int	nv
  )
  {
  	double	a;
  	RREAL	v0[2], v1[2];
  	register int	i;
  
  	a = 0.;
  	v0[0] = vl[1][0] - vl[0][0];
  	v0[1] = vl[1][1] - vl[0][1];
  	for (i = 2; i < nv; i++) {
  		v1[0] = vl[i][0] - vl[0][0];
  		v1[1] = vl[i][1] - vl[0][1];
  		a += v0[0]*v1[1] - v0[1]*v1[0];
  		v0[0] = v1[0]; v0[1] = v1[1];
  	}
  	return(a * (a >= 0. ? .5 : -.5));
  }
  
  
  static int
  convex_hull(		/* compute polygon's convex hull */
  	RREAL	vl[][2],
  	int	nv,
  	RREAL	vlo[][2]	/* return value */
  )
  {
  	int	nvo, nvt;
  	RREAL	vlt[MAXVERT][2];
  	double	voa, vta;
  	register int	i, j;
  					/* start with original polygon */
  	for (i = nvo = nv; i--; ) {
  		vlo[i][0] = vl[i][0]; vlo[i][1] = vl[i][1];
  	}
  	voa = poly_area(vlo, nvo);	/* compute its area */
  	for (i = 0; i < nvo; i++) {		/* for each output vertex */
  		for (j = 0; j < i; j++) {
  			vlt[j][0] = vlo[j][0]; vlt[j][1] = vlo[j][1];
  		}
  		nvt = nvo - 1;			/* make poly w/o vertex */
  		for (j = i; j < nvt; j++) {
  			vlt[j][0] = vlo[j+1][0]; vlt[j][1] = vlo[j+1][1];
  		}
  		vta = poly_area(vlt, nvt);
  		if (vta >= voa) {		/* is simpler poly bigger? */
  			voa = vta;			/* then use it */
  			for (j = nvo = nvt; j--; ) {
  				vlo[j][0] = vlt[j][0]; vlo[j][1] = vlt[j][1];
  			}
  			i--;				/* next adjust */
  		}
  	}
  	return(nvo);
  }
  
  
  static void
  spinsert(			/* insert new source polygon */
  	int	sn,
  	RREAL	vl[][2],
  	int	nv
  )
  {
  	register SPLIST	*spn;
  	register int	i;
  
  	if (nv < 3)
  		return;
  	if (nv > 3)
  		spn = (SPLIST *)malloc(sizeof(SPLIST)+sizeof(RREAL)*2*(nv-3));
  	else
  		spn = (SPLIST *)malloc(sizeof(SPLIST));
  	if (spn == NULL)
  		error(SYSTEM, "out of memory in spinsert");
  	spn->sn = sn;
  	for (i = spn->nv = nv; i--; ) {
  		spn->vl[i][0] = vl[i][0]; spn->vl[i][1] = vl[i][1];
  	}
  	spn->next = sphead;		/* push onto global list */
  	sphead = spn;
  }
  
  
  static int
  sourcepoly(			/* compute image polygon for source */
  	int	sn,
  	RREAL	sp[MAXVERT][2]
  )
  {
  	static short	cubeord[8][6] = {{1,3,2,6,4,5},{0,4,5,7,3,2},
  					 {0,1,3,7,6,4},{0,1,5,7,6,2},
  					 {0,2,6,7,5,1},{0,4,6,7,3,1},
  					 {0,2,3,7,5,4},{1,5,4,6,2,3}};
  	register SRCREC	*s = source + sn;
  	FVECT	ap, ip;
  	RREAL	pt[6][2];
  	int	dir;
  	register int	i, j;
  
  	if (s->sflags & (SDISTANT|SFLAT)) {
  		if (s->sflags & SDISTANT) {
  			if (ourview.type == VT_PAR)
  				return(0);	/* all or nothing case */
  			if (s->srad >= 0.05)
  				return(0);	/* should never be a problem */
  		}
  		if (s->sflags & SFLAT) {
  			for (i = 0; i < 3; i++)
  				ap[i] = s->sloc[i] - ourview.vp[i];
  			if (DOT(ap, s->snorm) >= 0.)
  				return(0);	/* source faces away */
  		}
  		for (j = 0; j < 4; j++) {	/* four corners */
  			for (i = 0; i < 3; i++) {
  				ap[i] = s->sloc[i];
  				if ((j==1)|(j==2)) ap[i] += s->ss[SU][i];
  				else ap[i] -= s->ss[SU][i];
  				if ((j==2)|(j==3)) ap[i] += s->ss[SV][i];
  				else ap[i] -= s->ss[SV][i];
  				if (s->sflags & SDISTANT) {
  					ap[i] *= 1. + ourview.vfore;
  					ap[i] += ourview.vp[i];
  				}
  			}
  			viewloc(ip, &ourview, ap);	/* find image point */
  			if (ip[2] <= 0.)
  				return(0);		/* in front of view */
  			sp[j][0] = ip[0]; sp[j][1] = ip[1];
  		}
  		return(4);
  	}
  					/* identify furthest corner */
  	for (i = 0; i < 3; i++)
  		ap[i] = s->sloc[i] - ourview.vp[i];
  	dir =	(DOT(ap,s->ss[SU])>0.) |
  		(DOT(ap,s->ss[SV])>0.)<<1 |
  		(DOT(ap,s->ss[SW])>0.)<<2 ;
  					/* order vertices based on this */
  	for (j = 0; j < 6; j++) {
  		for (i = 0; i < 3; i++) {
  			ap[i] = s->sloc[i];
  			if (cubeord[dir][j] & 1) ap[i] += s->ss[SU][i];
  			else ap[i] -= s->ss[SU][i];
  			if (cubeord[dir][j] & 2) ap[i] += s->ss[SV][i];
  			else ap[i] -= s->ss[SV][i];
  			if (cubeord[dir][j] & 4) ap[i] += s->ss[SW][i];
  			else ap[i] -= s->ss[SW][i];
  		}
  		viewloc(ip, &ourview, ap);	/* find image point */
  		if (ip[2] <= 0.)
  			return(0);		/* in front of view */
  		pt[j][0] = ip[0]; pt[j][1] = ip[1];
  	}
  	return(convex_hull(pt, 6, sp));		/* make sure it's convex */
  }
  
  
  			/* initialize by finding sources smaller than rad */
  extern void
  init_drawsources(
  	int	rad				/* source sample size */
  )
  {
  	RREAL	spoly[MAXVERT][2];
  	int	nsv;
  	register SPLIST	*sp;
  	register int	i;
  					/* free old source list if one */
  	for (sp = sphead; sp != NULL; sp = sphead) {
  		sphead = sp->next;
  		free((void *)sp);
  	}
  					/* loop through all sources */
  	for (i = nsources; i--; ) {
  					/* skip illum's */
  		if (findmaterial(source[i].so)->otype == MAT_ILLUM)
  			continue;
  					/* compute image polygon for source */
  		if (!(nsv = sourcepoly(i, spoly)))
  			continue;
  					/* clip to image boundaries */
  		if (!(nsv = box_clip_poly(spoly, nsv, 0., 1., 0., 1., spoly)))
  			continue;
  					/* big enough for standard sampling? */
  		if (minw2(spoly, nsv, ourview.vn2/ourview.hn2) >
  				(double)rad*rad/hres/hres)
  			continue;
  					/* OK, add to our list */
  		spinsert(i, spoly, nsv);
  	}
  }
  
  extern void			/* add sources smaller than rad to computed subimage */
  drawsources(
  	COLOR	*pic[],				/* subimage pixel value array */
  	float	*zbf[],				/* subimage distance array (opt.) */
  	int	x0,				/* origin and size of subimage */
  	int	xsiz,
  	int	y0,
  	int	ysiz
  )
  {
  	RREAL	spoly[MAXVERT][2], ppoly[MAXVERT][2];
  	int	nsv, npv;
  	int	xmin, xmax, ymin, ymax, x, y;
  	RREAL	cxy[2];
  	double	w;
  	RAY	sr;
  	register SPLIST	*sp;
  	register int	i;
  					/* check each source in our list */
  	for (sp = sphead; sp != NULL; sp = sp->next) {
  					/* clip source poly to subimage */
  		nsv = box_clip_poly(sp->vl, sp->nv,
  				(double)x0/hres, (double)(x0+xsiz)/hres,
  				(double)y0/vres, (double)(y0+ysiz)/vres, spoly);
  		if (!nsv)
  			continue;
  					/* find common subimage (BBox) */
  		xmin = x0 + xsiz; xmax = x0;
  		ymin = y0 + ysiz; ymax = y0;
  		for (i = 0; i < nsv; i++) {
  			if ((double)xmin/hres > spoly[i][0])
  				xmin = spoly[i][0]*hres + FTINY;
  			if ((double)xmax/hres < spoly[i][0])
  				xmax = spoly[i][0]*hres - FTINY;
  			if ((double)ymin/vres > spoly[i][1])
  				ymin = spoly[i][1]*vres + FTINY;
  			if ((double)ymax/vres < spoly[i][1])
  				ymax = spoly[i][1]*vres - FTINY;
  		}
  					/* evaluate each pixel in BBox */
  		for (y = ymin; y <= ymax; y++)
  			for (x = xmin; x <= xmax; x++) {
  							/* subarea for pixel */
  				npv = box_clip_poly(spoly, nsv,
  						(double)x/hres, (x+1.)/hres,
  						(double)y/vres, (y+1.)/vres,
  						ppoly);
  				if (!npv)
  					continue;	/* no overlap */
  				convex_center(ppoly, npv, cxy);
  				if ((sr.rmax = viewray(sr.rorg,sr.rdir,&ourview,
  						cxy[0],cxy[1])) < -FTINY)
  					continue;	/* not in view */
  				if (source[sp->sn].sflags & SSPOT &&
  						spotout(&sr, source[sp->sn].sl.s))
  					continue;	/* outside spot */
  				rayorigin(&sr, SHADOW, NULL, NULL);
  				sr.rsrc = sp->sn;
  				rayvalue(&sr);		/* compute value */
  				if (bright(sr.rcol) <= FTINY)
  					continue;	/* missed/blocked */
  							/* modify pixel */
  				w = poly_area(ppoly, npv) * hres * vres;
  				if (zbf[y-y0] != NULL &&
  						sr.rt < 0.99*zbf[y-y0][x-x0]) {
  					zbf[y-y0][x-x0] = sr.rt;
  				} else if (!bigdiff(sr.rcol, pic[y-y0][x-x0],
  						0.01)) { /* source sample */
  					scalecolor(pic[y-y0][x-x0], w);
  					continue;
  				}
  				scalecolor(sr.rcol, w);
  				scalecolor(pic[y-y0][x-x0], 1.-w);
  				addcolor(pic[y-y0][x-x0], sr.rcol);
  			}
  	}
  }
  