src/px/pcond4.c

/* Copyright (c) 1997 Regents of the University of California */

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

/*
 * Routines for veiling glare and loss of acuity.
 */

#include "pcond.h"

/************** VEILING STUFF *****************/

#define VADAPT          0.08            /* fraction of adaptation from veil */

static COLOR    *veilimg = NULL;        /* veiling image */

#define veilscan(y)     (veilimg+(y)*fvxr)

static float    (*raydir)[3] = NULL;    /* ray direction for each pixel */

#define rdirscan(y)     (raydir+(y)*fvxr)


compraydir()                            /* compute ray directions */
{
        FVECT   rorg, rdir;
        double  h, v;
        register int    x, y;

        if (raydir != NULL)             /* already done? */
                return;
        raydir = (float (*)[3])malloc(fvxr*fvyr*3*sizeof(float));
        if (raydir == NULL)
                syserror("malloc");

        for (y = 0; y < fvyr; y++) {
                switch (inpres.or) {
                case YMAJOR: case YMAJOR|XDECR:
                        v = (y+.5)/fvyr; break;
                case YMAJOR|YDECR: case YMAJOR|YDECR|XDECR:
                        v = 1. - (y+.5)/fvyr; break;
                case 0: case YDECR:
                        h = (y+.5)/fvyr; break;
                case XDECR: case XDECR|YDECR:
                        h = 1. - (y+.5)/fvyr; break;
                }
                for (x = 0; x < fvxr; x++) {
                        switch (inpres.or) {
                        case YMAJOR: case YMAJOR|YDECR:
                                h = (x+.5)/fvxr; break;
                        case YMAJOR|XDECR: case YMAJOR|XDECR|YDECR:
                                h = 1. - (x+.5)/fvxr; break;
                        case 0: case XDECR:
                                v = (x+.5)/fvxr; break;
                        case YDECR: case YDECR|XDECR:
                                v = 1. - (x+.5)/fvxr; break;
                        }
                        if (viewray(rorg, rdir, &ourview, h, v)
                                        >= -FTINY) {
                                rdirscan(y)[x][0] = rdir[0];
                                rdirscan(y)[x][1] = rdir[1];
                                rdirscan(y)[x][2] = rdir[2];
                        } else {
                                rdirscan(y)[x][0] =
                                rdirscan(y)[x][1] =
                                rdirscan(y)[x][2] = 0.0;
                        }
                }
        }
}


compveil()                              /* compute veiling image */
{
        double  t2, t2sum;
        COLOR   ctmp, vsum;
        int     px, py;
        register int    x, y;

        if (veilimg != NULL)            /* already done? */
                return;
                                        /* compute ray directions */
        compraydir();
                                        /* compute veil image */
        veilimg = (COLOR *)malloc(fvxr*fvyr*sizeof(COLOR));
        if (veilimg == NULL)
                syserror("malloc");
        for (py = 0; py < fvyr; py++)
                for (px = 0; px < fvxr; px++) {
                        t2sum = 0.;
                        setcolor(vsum, 0., 0., 0.);
                        for (y = 0; y < fvyr; y++)
                                for (x = 0; x < fvxr; x++) {
                                        if (x == px && y == py) continue;
                                        t2 = DOT(rdirscan(py)[px],
                                                        rdirscan(y)[x]);
                                        if (t2 <= FTINY) continue;
                                        /*      use approximation instead
                                        t3 = acos(t2);
                                        t2 = t2/(t3*t3);
                                        */
                                        t2 *= .5 / (1. - t2);
                                        copycolor(ctmp, fovscan(y)[x]);
                                        scalecolor(ctmp, t2);
                                        addcolor(vsum, ctmp);
                                        t2sum += t2;
                                }
                        /* VADAPT of original is subtracted in addveil() */
                        scalecolor(vsum, VADAPT/t2sum);
                        copycolor(veilscan(py)[px], vsum);
                }
                                        /* modify FOV sample image */
        for (y = 0; y < fvyr; y++)
                for (x = 0; x < fvxr; x++) {
                        scalecolor(fovscan(y)[x], 1.-VADAPT);
                        addcolor(fovscan(y)[x], veilscan(y)[x]);
                }
        comphist();                     /* recompute histogram */
}


addveil(sl, y)                          /* add veil to scanline */
COLOR   *sl;
int     y;
{
        int     vx, vy;
        double  dx, dy;
        double  lv, uv;
        register int    x, i;

        vy = dy = (y+.5)/numscans(&inpres)*fvyr - .5;
        while (vy >= fvyr-1) vy--;
        dy -= (double)vy;
        for (x = 0; x < scanlen(&inpres); x++) {
                vx = dx = (x+.5)/scanlen(&inpres)*fvxr - .5;
                while (vx >= fvxr-1) vx--;
                dx -= (double)vx;
                for (i = 0; i < 3; i++) {
                        lv = (1.-dy)*colval(veilscan(vy)[vx],i) +
                                        dy*colval(veilscan(vy+1)[vx],i);
                        uv = (1.-dy)*colval(veilscan(vy)[vx+1],i) +
                                        dy*colval(veilscan(vy+1)[vx+1],i);
                        colval(sl[x],i) = (1.-VADAPT)*colval(sl[x],i) +
                                        (1.-dx)*lv + dx*uv;
                }
        }
}


/****************** ACUITY STUFF *******************/

typedef struct {
        short   sampe;          /* sample area size (exponent of 2) */
        short   nscans;         /* number of scanlines in this bar */
        int     len;            /* individual scanline length */
        int     nread;          /* number of scanlines loaded */
        COLOR   *sdata;         /* scanbar data */
} SCANBAR;

#define bscan(sb,y)     ((COLOR *)(sb)->sdata+((y)%(sb)->nscans)*(sb)->len)

SCANBAR *rootbar;               /* root scan bar (lowest resolution) */

float   *inpacuD;               /* input acuity data (cycles/degree) */

#define tsampr(x,y)     inpacuD[(y)*fvxr+(x)]


double
hacuity(La)                     /* return visual acuity in cycles/degree */
double  La;
{
                                        /* functional fit */
        return(17.25*atan(1.4*log10(La) + 0.35) + 25.72);
}


COLOR *
getascan(sb, y)                 /* find/read scanline y for scanbar sb */
register SCANBAR        *sb;
int     y;
{
        register COLOR  *sl0, *sl1, *mysl;
        register int    i;

        if (y < sb->nread - sb->nscans)                 /* too far back? */
                return(NULL);
        for ( ; y >= sb->nread; sb->nread++) {          /* read as necessary */
                mysl = bscan(sb, sb->nread);
                if (sb->sampe == 0) {
                        if (freadscan(mysl, sb->len, infp) < 0) {
                                fprintf(stderr, "%s: %s: scanline read error\n",
                                                progname, infn);
                                exit(1);
                        }
                } else {
                        sl0 = getascan(sb+1, 2*y);
                        if (sl0 == NULL)
                                return(NULL);
                        sl1 = getascan(sb+1, 2*y+1);
                        for (i = 0; i < sb->len; i++) {
                                copycolor(mysl[i], sl0[2*i]);
                                addcolor(mysl[i], sl0[2*i+1]);
                                addcolor(mysl[i], sl1[2*i]);
                                addcolor(mysl[i], sl1[2*i+1]);
                                scalecolor(mysl[i], 0.25);
                        }
                }
        }
        return(bscan(sb, y));
}


acuscan(scln, y)                /* get acuity-sampled scanline */
COLOR   *scln;
int     y;
{
        double  sr;
        double  dx, dy;
        int     ix, iy;
        register int    x;
                                        /* compute foveal y position */
        iy = dy = (y+.5)/numscans(&inpres)*fvyr - .5;
        while (iy >= fvyr-1) iy--;
        dy -= (double)iy;
        for (x = 0; x < scanlen(&inpres); x++) {
                                        /* compute foveal x position */
                ix = dx = (x+.5)/scanlen(&inpres)*fvxr - .5;
                while (ix >= fvxr-1) ix--;
                dx -= (double)ix;
                                        /* interpolate sample rate */
                sr = (1.-dy)*((1.-dx)*tsampr(ix,iy) + dx*tsampr(ix+1,iy)) +
                        dy*((1.-dx)*tsampr(ix,iy+1) + dx*tsampr(ix+1,iy+1));

                acusample(scln[x], x, y, sr);   /* compute sample */
        }
}


acusample(col, x, y, sr)        /* interpolate sample at (x,y) using rate sr */
COLOR   col;
int     x, y;
double  sr;
{
        COLOR   c1;
        double  d;
        register SCANBAR        *sb0;

        for (sb0 = rootbar; sb0->sampe != 0 && 1<<sb0[1].sampe > sr; sb0++)
                ;
        ascanval(col, x, y, sb0);
        if (sb0->sampe == 0)            /* don't extrapolate highest */
                return;
        ascanval(c1, x, y, sb0+1);
        d = ((1<<sb0->sampe) - sr)/(1<<sb0[1].sampe);
        scalecolor(col, 1.-d);
        scalecolor(c1, d);
        addcolor(col, c1);
}


ascanval(col, x, y, sb)         /* interpolate scanbar at orig. coords (x,y) */
COLOR   col;
int     x, y;
SCANBAR *sb;
{
        COLOR   *sl0, *sl1, c1, c1y;
        double  dx, dy;
        int     ix, iy;

        if (sb->sampe == 0) {           /* no need to interpolate */
                sl0 = getascan(sb, y);
                copycolor(col, sl0[x]);
                return;
        }
                                        /* compute coordinates for sb */
        ix = dx = (x+.5)/(1<<sb->sampe) - .5;
        while (ix >= sb->len-1) ix--;
        dx -= (double)ix;
        iy = dy = (y+.5)/(1<<sb->sampe) - .5;
        while (iy >= (numscans(&inpres)>>sb->sampe)-1) iy--;
        dy -= (double)iy;
                                        /* get scanlines */
        sl0 = getascan(sb, iy);
#ifdef DEBUG
        if (sl0 == NULL)
                error(INTERNAL, "cannot backspace in ascanval");
#endif
        sl1 = getascan(sb, iy+1);
                                        /* 2D linear interpolation */
        copycolor(col, sl0[ix]);
        scalecolor(col, 1.-dx);
        copycolor(c1, sl0[ix+1]);
        scalecolor(c1, dx);
        addcolor(col, c1);
        copycolor(c1y, sl1[ix]);
        scalecolor(c1y, 1.-dx);
        copycolor(c1, sl1[ix+1]);
        scalecolor(c1, dx);
        addcolor(c1y, c1);
        scalecolor(col, 1.-dy);
        scalecolor(c1y, dy);
        addcolor(col, c1y);
        for (ix = 0; ix < 3; ix++)      /* make sure no negative */
                if (colval(col,ix) < 0.)
                        colval(col,ix) = 0.;
}


SCANBAR *
sballoc(se, ns, sl)             /* allocate scanbar */
int     se;             /* sampling rate exponent */
int     ns;             /* number of scanlines */
int     sl;             /* original scanline length */
{
        SCANBAR *sbarr;
        register SCANBAR        *sb;

        sbarr = sb = (SCANBAR *)malloc((se+1)*sizeof(SCANBAR));
        if (sb == NULL)
                syserror("malloc");
        do {
                sb->sampe = se;
                sb->len = sl>>se;
                sb->nscans = ns;
                sb->sdata = (COLOR *)malloc(sb->len*ns*sizeof(COLOR));
                if (sb->sdata == NULL)
                        syserror("malloc");
                sb->nread = 0;
                ns <<= 1;
                sb++;
        } while (--se >= 0);
        return(sbarr);
}


initacuity()                    /* initialize variable acuity sampling */
{
        FVECT   diffx, diffy, cp;
        double  omega, maxsr;
        register int    x, y, i;

        compraydir();                   /* compute ray directions */

        inpacuD = (float *)malloc(fvxr*fvyr*sizeof(float));
        if (inpacuD == NULL)
                syserror("malloc");
        maxsr = 1.;                     /* compute internal sample rates */
        for (y = 1; y < fvyr-1; y++)
                for (x = 1; x < fvxr-1; x++) {
                        for (i = 0; i < 3; i++) {
                                diffx[i] = 0.5*fvxr/scanlen(&inpres) *
                                                (rdirscan(y)[x+1][i] -
                                                rdirscan(y)[x-1][i]);
                                diffy[i] = 0.5*fvyr/numscans(&inpres) *
                                                (rdirscan(y+1)[x][i] -
                                                rdirscan(y-1)[x][i]);
                        }
                        fcross(cp, diffx, diffy);
                        omega = 0.5 * sqrt(DOT(cp,cp));
                        if (omega <= FTINY*FTINY)
                                tsampr(x,y) = 1.;
                        else if ((tsampr(x,y) = PI/180. / sqrt(omega) /
                                        hacuity(plum(fovscan(y)[x]))) > maxsr)
                                maxsr = tsampr(x,y);
                }
                                        /* copy perimeter (easier) */
        for (x = 1; x < fvxr-1; x++) {
                tsampr(x,0) = tsampr(x,1);
                tsampr(x,fvyr-1) = tsampr(x,fvyr-2);
        }
        for (y = 0; y < fvyr; y++) {
                tsampr(0,y) = tsampr(1,y);
                tsampr(fvxr-1,y) = tsampr(fvxr-2,y);
        }
                                        /* initialize with next power of two */
        rootbar = sballoc((int)(log(maxsr)/log(2.))+1, 2, scanlen(&inpres));
}
Revision:	3.14
Committed:	Tue Jan 28 16:31:17 1997 UTC (27 years, 3 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 3.13:	+2 -5 lines
Log Message:	removed unnecessary debugging statements
#	User	Rev	Content
1	greg	3.13	/* Copyright (c) 1997 Regents of the University of California */
2	greg	3.1
3			#ifndef lint
4			static char SCCSid[] = "$SunId$ LBL";
5			#endif
6
7			/*
8			* Routines for veiling glare and loss of acuity.
9			*/
10
11			#include "pcond.h"
12
13	greg	3.3	/************ VEILING STUFF ***************/
14	greg	3.1
15			#define VADAPT 0.08 /* fraction of adaptation from veil */
16
17	greg	3.11	static COLOR veilimg = NULL; / veiling image */
18	greg	3.1
19			#define veilscan(y) (veilimg+(y)*fvxr)
20
21	greg	3.2	static float (raydir)[3] = NULL; / ray direction for each pixel */
22	greg	3.1
23			#define rdirscan(y) (raydir+(y)*fvxr)
24
25
26			compraydir() /* compute ray directions */
27			{
28	greg	3.2	FVECT rorg, rdir;
29	greg	3.1	double h, v;
30			register int x, y;
31
32			if (raydir != NULL) /* already done? */
33			return;
34	greg	3.2	raydir = (float ()[3])malloc(fvxrfvyr3sizeof(float));
35	greg	3.1	if (raydir == NULL)
36			syserror("malloc");
37
38			for (y = 0; y < fvyr; y++) {
39			switch (inpres.or) {
40			case YMAJOR: case YMAJOR\|XDECR:
41			v = (y+.5)/fvyr; break;
42			case YMAJOR\|YDECR: case YMAJOR\|YDECR\|XDECR:
43			v = 1. - (y+.5)/fvyr; break;
44			case 0: case YDECR:
45			h = (y+.5)/fvyr; break;
46			case XDECR: case XDECR\|YDECR:
47			h = 1. - (y+.5)/fvyr; break;
48			}
49			for (x = 0; x < fvxr; x++) {
50			switch (inpres.or) {
51			case YMAJOR: case YMAJOR\|YDECR:
52			h = (x+.5)/fvxr; break;
53			case YMAJOR\|XDECR: case YMAJOR\|XDECR\|YDECR:
54			h = 1. - (x+.5)/fvxr; break;
55			case 0: case XDECR:
56			v = (x+.5)/fvxr; break;
57			case YDECR: case YDECR\|XDECR:
58			v = 1. - (x+.5)/fvxr; break;
59			}
60	greg	3.2	if (viewray(rorg, rdir, &ourview, h, v)
61			>= -FTINY) {
62			rdirscan(y)[x][0] = rdir[0];
63			rdirscan(y)[x][1] = rdir[1];
64			rdirscan(y)[x][2] = rdir[2];
65			} else {
66	greg	3.1	rdirscan(y)[x][0] =
67			rdirscan(y)[x][1] =
68			rdirscan(y)[x][2] = 0.0;
69			}
70			}
71			}
72			}
73
74
75			compveil() /* compute veiling image */
76			{
77			double t2, t2sum;
78			COLOR ctmp, vsum;
79			int px, py;
80			register int x, y;
81	greg	3.11
82			if (veilimg != NULL) /* already done? */
83			return;
84	greg	3.1	/* compute ray directions */
85			compraydir();
86			/* compute veil image */
87			veilimg = (COLOR )malloc(fvxrfvyr*sizeof(COLOR));
88			if (veilimg == NULL)
89			syserror("malloc");
90			for (py = 0; py < fvyr; py++)
91			for (px = 0; px < fvxr; px++) {
92			t2sum = 0.;
93			setcolor(vsum, 0., 0., 0.);
94			for (y = 0; y < fvyr; y++)
95			for (x = 0; x < fvxr; x++) {
96			if (x == px && y == py) continue;
97			t2 = DOT(rdirscan(py)[px],
98			rdirscan(y)[x]);
99			if (t2 <= FTINY) continue;
100	greg	3.4	/* use approximation instead
101	greg	3.12	t3 = acos(t2);
102			t2 = t2/(t3*t3);
103	greg	3.4	*/
104	greg	3.12	t2 *= .5 / (1. - t2);
105	greg	3.1	copycolor(ctmp, fovscan(y)[x]);
106			scalecolor(ctmp, t2);
107			addcolor(vsum, ctmp);
108			t2sum += t2;
109			}
110			/* VADAPT of original is subtracted in addveil() */
111			scalecolor(vsum, VADAPT/t2sum);
112			copycolor(veilscan(py)[px], vsum);
113			}
114	greg	3.11	/* modify FOV sample image */
115			for (y = 0; y < fvyr; y++)
116			for (x = 0; x < fvxr; x++) {
117			scalecolor(fovscan(y)[x], 1.-VADAPT);
118			addcolor(fovscan(y)[x], veilscan(y)[x]);
119			}
120			comphist(); /* recompute histogram */
121	greg	3.1	}
122
123
124			addveil(sl, y) /* add veil to scanline */
125			COLOR *sl;
126			int y;
127			{
128			int vx, vy;
129			double dx, dy;
130			double lv, uv;
131			register int x, i;
132
133			vy = dy = (y+.5)/numscans(&inpres)*fvyr - .5;
134	greg	3.7	while (vy >= fvyr-1) vy--;
135	greg	3.1	dy -= (double)vy;
136			for (x = 0; x < scanlen(&inpres); x++) {
137			vx = dx = (x+.5)/scanlen(&inpres)*fvxr - .5;
138	greg	3.7	while (vx >= fvxr-1) vx--;
139	greg	3.1	dx -= (double)vx;
140			for (i = 0; i < 3; i++) {
141			lv = (1.-dy)*colval(veilscan(vy)[vx],i) +
142			dy*colval(veilscan(vy+1)[vx],i);
143			uv = (1.-dy)*colval(veilscan(vy)[vx+1],i) +
144			dy*colval(veilscan(vy+1)[vx+1],i);
145			colval(sl[x],i) = (1.-VADAPT)*colval(sl[x],i) +
146			(1.-dx)lv + dxuv;
147			}
148			}
149	greg	3.3	}
150
151
152			/**************** ACUITY STUFF *****************/
153
154	greg	3.8	typedef struct {
155			short sampe; /* sample area size (exponent of 2) */
156	greg	3.3	short nscans; /* number of scanlines in this bar */
157			int len; /* individual scanline length */
158			int nread; /* number of scanlines loaded */
159	greg	3.8	COLOR sdata; / scanbar data */
160	greg	3.3	} SCANBAR;
161
162	greg	3.8	#define bscan(sb,y) ((COLOR )(sb)->sdata+((y)%(sb)->nscans)(sb)->len)
163	greg	3.3
164			SCANBAR rootbar; / root scan bar (lowest resolution) */
165
166			float inpacuD; / input acuity data (cycles/degree) */
167
168			#define tsampr(x,y) inpacuD[(y)*fvxr+(x)]
169
170
171			double
172			hacuity(La) /* return visual acuity in cycles/degree */
173			double La;
174	greg	3.13	{
175			/* functional fit */
176			return(17.25atan(1.4log10(La) + 0.35) + 25.72);
177	greg	3.3	}
178
179
180			COLOR *
181			getascan(sb, y) /* find/read scanline y for scanbar sb */
182			register SCANBAR *sb;
183			int y;
184			{
185			register COLOR sl0, sl1, *mysl;
186			register int i;
187
188	greg	3.6	if (y < sb->nread - sb->nscans) /* too far back? */
189			return(NULL);
190	greg	3.3	for ( ; y >= sb->nread; sb->nread++) { /* read as necessary */
191			mysl = bscan(sb, sb->nread);
192	greg	3.8	if (sb->sampe == 0) {
193	greg	3.3	if (freadscan(mysl, sb->len, infp) < 0) {
194			fprintf(stderr, "%s: %s: scanline read error\n",
195			progname, infn);
196			exit(1);
197			}
198			} else {
199	greg	3.8	sl0 = getascan(sb+1, 2*y);
200	greg	3.6	if (sl0 == NULL)
201			return(NULL);
202	greg	3.8	sl1 = getascan(sb+1, 2*y+1);
203	greg	3.3	for (i = 0; i < sb->len; i++) {
204			copycolor(mysl[i], sl0[2*i]);
205			addcolor(mysl[i], sl0[2*i+1]);
206			addcolor(mysl[i], sl1[2*i]);
207			addcolor(mysl[i], sl1[2*i+1]);
208			scalecolor(mysl[i], 0.25);
209			}
210			}
211			}
212			return(bscan(sb, y));
213			}
214
215
216			acuscan(scln, y) /* get acuity-sampled scanline */
217			COLOR *scln;
218			int y;
219			{
220			double sr;
221			double dx, dy;
222			int ix, iy;
223			register int x;
224			/* compute foveal y position */
225			iy = dy = (y+.5)/numscans(&inpres)*fvyr - .5;
226	greg	3.9	while (iy >= fvyr-1) iy--;
227	greg	3.3	dy -= (double)iy;
228			for (x = 0; x < scanlen(&inpres); x++) {
229			/* compute foveal x position */
230			ix = dx = (x+.5)/scanlen(&inpres)*fvxr - .5;
231	greg	3.9	while (ix >= fvxr-1) ix--;
232	greg	3.3	dx -= (double)ix;
233			/* interpolate sample rate */
234			sr = (1.-dy)((1.-dx)tsampr(ix,iy) + dx*tsampr(ix+1,iy)) +
235			dy((1.-dx)tsampr(ix,iy+1) + dx*tsampr(ix+1,iy+1));
236
237			acusample(scln[x], x, y, sr); /* compute sample */
238			}
239			}
240
241
242			acusample(col, x, y, sr) /* interpolate sample at (x,y) using rate sr */
243			COLOR col;
244			int x, y;
245			double sr;
246			{
247			COLOR c1;
248			double d;
249			register SCANBAR *sb0;
250
251	greg	3.8	for (sb0 = rootbar; sb0->sampe != 0 && 1<<sb0[1].sampe > sr; sb0++)
252	greg	3.3	;
253			ascanval(col, x, y, sb0);
254	greg	3.8	if (sb0->sampe == 0) /* don't extrapolate highest */
255	greg	3.3	return;
256	greg	3.8	ascanval(c1, x, y, sb0+1);
257			d = ((1<<sb0->sampe) - sr)/(1<<sb0[1].sampe);
258	greg	3.3	scalecolor(col, 1.-d);
259			scalecolor(c1, d);
260			addcolor(col, c1);
261			}
262
263
264			ascanval(col, x, y, sb) /* interpolate scanbar at orig. coords (x,y) */
265			COLOR col;
266			int x, y;
267			SCANBAR *sb;
268			{
269			COLOR sl0, sl1, c1, c1y;
270			double dx, dy;
271			int ix, iy;
272
273	greg	3.8	if (sb->sampe == 0) { /* no need to interpolate */
274	greg	3.6	sl0 = getascan(sb, y);
275			copycolor(col, sl0[x]);
276			return;
277			}
278			/* compute coordinates for sb */
279	greg	3.8	ix = dx = (x+.5)/(1<<sb->sampe) - .5;
280	greg	3.7	while (ix >= sb->len-1) ix--;
281	greg	3.3	dx -= (double)ix;
282	greg	3.8	iy = dy = (y+.5)/(1<<sb->sampe) - .5;
283			while (iy >= (numscans(&inpres)>>sb->sampe)-1) iy--;
284	greg	3.3	dy -= (double)iy;
285			/* get scanlines */
286			sl0 = getascan(sb, iy);
287	greg	3.9	#ifdef DEBUG
288	greg	3.14	if (sl0 == NULL)
289			error(INTERNAL, "cannot backspace in ascanval");
290	greg	3.9	#endif
291	greg	3.3	sl1 = getascan(sb, iy+1);
292			/* 2D linear interpolation */
293			copycolor(col, sl0[ix]);
294			scalecolor(col, 1.-dx);
295			copycolor(c1, sl0[ix+1]);
296			scalecolor(c1, dx);
297			addcolor(col, c1);
298			copycolor(c1y, sl1[ix]);
299			scalecolor(c1y, 1.-dx);
300			copycolor(c1, sl1[ix+1]);
301			scalecolor(c1, dx);
302			addcolor(c1y, c1);
303			scalecolor(col, 1.-dy);
304			scalecolor(c1y, dy);
305			addcolor(col, c1y);
306	greg	3.9	for (ix = 0; ix < 3; ix++) /* make sure no negative */
307			if (colval(col,ix) < 0.)
308			colval(col,ix) = 0.;
309	greg	3.3	}
310
311
312			SCANBAR *
313	greg	3.9	sballoc(se, ns, sl) /* allocate scanbar */
314			int se; /* sampling rate exponent */
315	greg	3.3	int ns; /* number of scanlines */
316			int sl; /* original scanline length */
317			{
318	greg	3.8	SCANBAR *sbarr;
319	greg	3.3	register SCANBAR *sb;
320
321	greg	3.9	sbarr = sb = (SCANBAR )malloc((se+1)sizeof(SCANBAR));
322	greg	3.3	if (sb == NULL)
323			syserror("malloc");
324	greg	3.8	do {
325	greg	3.9	sb->sampe = se;
326			sb->len = sl>>se;
327			sb->nscans = ns;
328			sb->sdata = (COLOR )malloc(sb->lenns*sizeof(COLOR));
329	greg	3.8	if (sb->sdata == NULL)
330			syserror("malloc");
331			sb->nread = 0;
332			ns <<= 1;
333			sb++;
334	greg	3.9	} while (--se >= 0);
335	greg	3.8	return(sbarr);
336	greg	3.3	}
337
338
339			initacuity() /* initialize variable acuity sampling */
340			{
341			FVECT diffx, diffy, cp;
342			double omega, maxsr;
343			register int x, y, i;
344
345			compraydir(); /* compute ray directions */
346
347			inpacuD = (float )malloc(fvxrfvyr*sizeof(float));
348			if (inpacuD == NULL)
349			syserror("malloc");
350			maxsr = 1.; /* compute internal sample rates */
351			for (y = 1; y < fvyr-1; y++)
352			for (x = 1; x < fvxr-1; x++) {
353			for (i = 0; i < 3; i++) {
354			diffx[i] = 0.5fvxr/scanlen(&inpres)
355			(rdirscan(y)[x+1][i] -
356			rdirscan(y)[x-1][i]);
357			diffy[i] = 0.5fvyr/numscans(&inpres)
358			(rdirscan(y+1)[x][i] -
359			rdirscan(y-1)[x][i]);
360			}
361			fcross(cp, diffx, diffy);
362			omega = 0.5 * sqrt(DOT(cp,cp));
363	greg	3.10	if (omega <= FTINY*FTINY)
364	greg	3.4	tsampr(x,y) = 1.;
365			else if ((tsampr(x,y) = PI/180. / sqrt(omega) /
366			hacuity(plum(fovscan(y)[x]))) > maxsr)
367	greg	3.3	maxsr = tsampr(x,y);
368			}
369			/* copy perimeter (easier) */
370			for (x = 1; x < fvxr-1; x++) {
371			tsampr(x,0) = tsampr(x,1);
372			tsampr(x,fvyr-1) = tsampr(x,fvyr-2);
373			}
374			for (y = 0; y < fvyr; y++) {
375	greg	3.9	tsampr(0,y) = tsampr(1,y);
376			tsampr(fvxr-1,y) = tsampr(fvxr-2,y);
377	greg	3.3	}
378			/* initialize with next power of two */
379	greg	3.8	rootbar = sballoc((int)(log(maxsr)/log(2.))+1, 2, scanlen(&inpres));
380	greg	3.1	}