/* Copyright (c) 1986 Regents of the University of California */

#ifndef lint
static char SCCSid[] = "$SunId$ LBL";
#endif

/*
 *  raytrace.c - routines for tracing and shading rays.
 *
 *     8/7/85
 */

#include  "ray.h"

#include  "octree.h"

#include  "otypes.h"

extern CUBE  thescene;			/* our scene */
extern int  maxdepth;			/* maximum recursion depth */
extern double  minweight;		/* minimum ray weight */

long  nrays = 0L;			/* number of rays traced */

#define  MAXLOOP	128		/* modifier loop detection */

#define  RAYHIT		(-1)		/* return value for intercepted ray */


rayorigin(r, ro, rt, rw)		/* start new ray from old one */
register RAY  *r, *ro;
int  rt;
double  rw;
{
	if ((r->parent = ro) == NULL) {		/* primary ray */
		r->rlvl = 0;
		r->rweight = rw;
		r->crtype = r->rtype = rt;
		r->rsrc = -1;
		r->clipset = NULL;
	} else {				/* spawned ray */
		r->rlvl = ro->rlvl;
		if (rt & RAYREFL) {
			r->rlvl++;
			r->rsrc = -1;
			r->clipset = ro->clipset;
		} else {
			r->rsrc = ro->rsrc;
			r->clipset = ro->newcset;
		}
		r->rweight = ro->rweight * rw;
		r->crtype = ro->crtype | (r->rtype = rt);
		VCOPY(r->rorg, ro->rop);
	}
	r->rno = nrays;
	r->newcset = r->clipset;
	r->ro = NULL;
	r->rot = FHUGE;
	r->pert[0] = r->pert[1] = r->pert[2] = 0.0;
	setcolor(r->pcol, 1.0, 1.0, 1.0);
	setcolor(r->rcol, 0.0, 0.0, 0.0);
	r->rt = 0.0;
	return(r->rlvl <= maxdepth && r->rweight >= minweight ? 0 : -1);
}


rayvalue(r)			/* compute a ray's value */
RAY  *r;
{
	extern int  (*trace)();

	if (localhit(r, &thescene) || sourcehit(r))
		raycont(r);

	if (trace != NULL)
		(*trace)(r);		/* trace execution */
}


raycont(r)			/* check for clipped object and continue */
register RAY  *r;
{
	if (r->clipset != NULL && inset(r->clipset, r->ro->omod))
		raytrans(r);
	else
		rayshade(r, r->ro->omod);
}


raytrans(r)			/* transmit ray as is */
register RAY  *r;
{
	RAY  tr;

	if (rayorigin(&tr, r, TRANS, 1.0) == 0) {
		VCOPY(tr.rdir, r->rdir);
		rayvalue(&tr);
		copycolor(r->rcol, tr.rcol);
		r->rt = r->rot + tr.rt;
	}
}


rayshade(r, mod)		/* shade ray r with material mod */
register RAY  *r;
int  mod;
{
	static int  depth = 0;
	register OBJREC  *m;
					/* check for infinite loop */
	if (depth++ >= MAXLOOP)
		objerror(r->ro, USER, "possible modifier loop");
	for ( ; mod != OVOID; mod = m->omod) {
		m = objptr(mod);
		/****** unnecessary test since modifier() is always called
		if (!ismodifier(m->otype)) {
			sprintf(errmsg, "illegal modifier \"%s\"", m->oname);
			error(USER, errmsg);
		}
		******/
		(*ofun[m->otype].funp)(m, r);	/* execute function */
		m->lastrno = r->rno;
		if (ismaterial(m->otype)) {	/* materials call raytexture */
			depth--;
			return;		/* we're done */
		}
	}
	objerror(r->ro, USER, "material not found");
}


raytexture(r, mod)			/* get material modifiers */
RAY  *r;
int  mod;
{
	static int  depth = 0;
	register OBJREC  *m;
					/* check for infinite loop */
	if (depth++ >= MAXLOOP)
		objerror(r->ro, USER, "modifier loop");
					/* execute textures and patterns */
	for ( ; mod != OVOID; mod = m->omod) {
		m = objptr(mod);
		if (!istexture(m->otype)) {
			sprintf(errmsg, "illegal modifier \"%s\"", m->oname);
			error(USER, errmsg);
		}
		(*ofun[m->otype].funp)(m, r);
		m->lastrno = r->rno;
	}
	depth--;			/* end here */
}


raymixture(r, fore, back, coef)		/* mix modifiers */
register RAY  *r;
OBJECT  fore, back;
double  coef;
{
	FVECT  curpert, forepert, backpert;
	COLOR  curpcol, forepcol, backpcol;
	register int  i;
					/* clip coefficient */
	if (coef > 1.0)
		coef = 1.0;
	else if (coef < 0.0)
		coef = 0.0;
					/* save current mods */
	VCOPY(curpert, r->pert);
	copycolor(curpcol, r->pcol);
					/* compute new mods */
						/* foreground */
	r->pert[0] = r->pert[1] = r->pert[2] = 0.0;
	setcolor(r->pcol, 1.0, 1.0, 1.0);
	if (fore != OVOID && coef > FTINY)
		raytexture(r, fore);
	VCOPY(forepert, r->pert);
	copycolor(forepcol, r->pcol);
						/* background */
	r->pert[0] = r->pert[1] = r->pert[2] = 0.0;
	setcolor(r->pcol, 1.0, 1.0, 1.0);
	if (back != OVOID && coef < 1.0-FTINY)
		raytexture(r, back);
	VCOPY(backpert, r->pert);
	copycolor(backpcol, r->pcol);
					/* sum perturbations */
	for (i = 0; i < 3; i++)
		r->pert[i] = curpert[i] + coef*forepert[i] +
				(1.0-coef)*backpert[i];
					/* multiply colors */
	setcolor(r->pcol, coef*colval(forepcol,RED) +
				(1.0-coef)*colval(backpcol,RED),
			coef*colval(forepcol,GRN) +
				(1.0-coef)*colval(backpcol,GRN),
			coef*colval(forepcol,BLU) +
				(1.0-coef)*colval(backpcol,BLU));
	multcolor(r->pcol, curpcol);
}


double
raynormal(norm, r)		/* compute perturbed normal for ray */
FVECT  norm;
register RAY  *r;
{
	double  newdot;
	register int  i;

	/*	The perturbation is added to the surface normal to obtain
	 *  the new normal.  If the new normal would affect the surface
	 *  orientation wrt. the ray, a correction is made.  The method is
	 *  still fraught with problems since reflected rays and similar
	 *  directions calculated from the surface normal may spawn rays behind
	 *  the surface.  The only solution is to curb textures at high
	 *  incidence (namely, keep DOT(rdir,pert) < Rdot).
	 */

	for (i = 0; i < 3; i++)
		norm[i] = r->ron[i] + r->pert[i];

	if (normalize(norm) == 0.0) {
		objerror(r->ro, WARNING, "illegal normal perturbation");
		VCOPY(norm, r->ron);
		return(r->rod);
	}
	newdot = -DOT(norm, r->rdir);
	if ((newdot > 0.0) != (r->rod > 0.0)) {		/* fix orientation */
		for (i = 0; i < 3; i++)
			norm[i] += 2.0*newdot*r->rdir[i];
		newdot = -newdot;
	}
	return(newdot);
}


flipsurface(r)			/* reverse surface orientation */
register RAY  *r;
{
	r->rod = -r->rod;
	r->ron[0] = -r->ron[0];
	r->ron[1] = -r->ron[1];
	r->ron[2] = -r->ron[2];
	r->pert[0] = -r->pert[0];
	r->pert[1] = -r->pert[1];
	r->pert[2] = -r->pert[2];
}


localhit(r, scene)		/* check for hit in the octree */
register RAY  *r;
register CUBE  *scene;
{
	FVECT  curpos;			/* current cube position */
	int  mpos, mneg;		/* sign flags */
	double  t, dt;
	register int  i;

	nrays++;			/* increment trace counter */

	mpos = mneg = 0;
	for (i = 0; i < 3; i++) {
		curpos[i] = r->rorg[i];
		if (r->rdir[i] > FTINY)
			mpos |= 1 << i;
		else if (r->rdir[i] < -FTINY)
			mneg |= 1 << i;
	}
	t = 0.0;
	if (!incube(scene, curpos)) {
					/* find distance to entry */
		for (i = 0; i < 3; i++) {
					/* plane in our direction */
			if (mpos & 1<<i)
				dt = scene->cuorg[i];
			else if (mneg & 1<<i)
				dt = scene->cuorg[i] + scene->cusize;
			else
				continue;
					/* distance to the plane */
			dt = (dt - r->rorg[i])/r->rdir[i];
			if (dt > t)
				t = dt;	/* farthest face is the one */
		}
		t += FTINY;		/* fudge to get inside cube */
					/* advance position */
		for (i = 0; i < 3; i++)
			curpos[i] += r->rdir[i]*t;

		if (!incube(scene, curpos))	/* non-intersecting ray */
			return(0);
	}
	return(raymove(curpos, mpos, mneg, r, scene) == RAYHIT);
}


static int
raymove(pos, plus, minus, r, cu)	/* check for hit as we move */
FVECT  pos;			/* modified */
int  plus, minus;		/* direction indicators to speed tests */
register RAY  *r;
register CUBE  *cu;
{
	int  ax;
	double  dt, t;
	register int  sgn;

	if (istree(cu->cutree)) {		/* recurse on subcubes */
		CUBE  cukid;
		register int  br;

		cukid.cusize = cu->cusize * 0.5;	/* find subcube */
		VCOPY(cukid.cuorg, cu->cuorg);
		br = 0;
		if (pos[0] >= cukid.cuorg[0]+cukid.cusize) {
			cukid.cuorg[0] += cukid.cusize;
			br |= 1;
		}
		if (pos[1] >= cukid.cuorg[1]+cukid.cusize) {
			cukid.cuorg[1] += cukid.cusize;
			br |= 2;
		}
		if (pos[2] >= cukid.cuorg[2]+cukid.cusize) {
			cukid.cuorg[2] += cukid.cusize;
			br |= 4;
		}
		for ( ; ; ) {
			cukid.cutree = octkid(cu->cutree, br);
			if ((ax = raymove(pos,plus,minus,r,&cukid)) == RAYHIT)
				return(RAYHIT);
			sgn = 1 << ax;
			if (sgn & minus)		/* negative axis? */
				if (sgn & br) {
					cukid.cuorg[ax] -= cukid.cusize;
					br &= ~sgn;
				} else
					return(ax);	/* underflow */
			else
				if (sgn & br)
					return(ax);	/* overflow */
				else {
					cukid.cuorg[ax] += cukid.cusize;
					br |= sgn;
				}
		}
		/*NOTREACHED*/
	}
	if (isfull(cu->cutree) && checkhit(r, cu))
		return(RAYHIT);
					/* advance to next cube */
	sgn = plus | minus;
	if (sgn&1) {
		dt = plus&1 ? cu->cuorg[0] + cu->cusize : cu->cuorg[0];
		t = (dt - pos[0])/r->rdir[0];
		ax = 0;
	} else
		t = FHUGE;
	if (sgn&2) {
		dt = plus&2 ? cu->cuorg[1] + cu->cusize : cu->cuorg[1];
		dt = (dt - pos[1])/r->rdir[1];
		if (dt < t) {
			t = dt;
			ax = 1;
		}
	}
	if (sgn&4) {
		dt = plus&4 ? cu->cuorg[2] + cu->cusize : cu->cuorg[2];
		dt = (dt - pos[2])/r->rdir[2];
		if (dt < t) {
			t = dt;
			ax = 2;
		}
	}
	pos[0] += r->rdir[0]*t;
	pos[1] += r->rdir[1]*t;
	pos[2] += r->rdir[2]*t;
	return(ax);
}


static
checkhit(r, cu)			/* check for hit in full cube */
register RAY  *r;
CUBE  *cu;
{
	OBJECT  oset[MAXSET+1];
	register OBJREC  *o;
	register int  i;

	objset(oset, cu->cutree);
	for (i = oset[0]; i > 0; i--) {
		o = objptr(oset[i]);
		if (o->lastrno == r->rno)		/* checked already? */
			continue;
		(*ofun[o->otype].funp)(o, r);
		o->lastrno = r->rno;
	}
	if (r->ro == NULL)
		return(0);			/* no scores yet */

	return(incube(cu, r->rop));		/* hit OK if in current cube */
}