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greg |
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#ifndef lint
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static const char RCSid[] = "$Id$";
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#endif
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/*
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* Radial basis function representation for BSDF data.
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*
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* G. Ward
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*/
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#define _USE_MATH_DEFINES
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <math.h>
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#include "bsdfrep.h"
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#ifndef RSCA
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#define RSCA 2.7 /* radius scaling factor (empirical) */
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#endif
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/* our loaded grid for this incident angle */
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GRIDVAL dsf_grid[GRIDRES][GRIDRES];
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/* Start new DSF input grid */
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void
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new_bsdf_data(double new_theta, double new_phi)
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{
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if (!new_input_direction(new_theta, new_phi))
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exit(1);
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memset(dsf_grid, 0, sizeof(dsf_grid));
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}
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/* Add BSDF data point */
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void
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add_bsdf_data(double theta_out, double phi_out, double val, int isDSF)
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{
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FVECT ovec;
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int pos[2];
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if (!output_orient) /* check output orientation */
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output_orient = 1 - 2*(theta_out > 90.);
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else if (output_orient > 0 ^ theta_out < 90.) {
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fputs("Cannot handle output angles on both sides of surface\n",
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stderr);
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exit(1);
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}
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ovec[2] = sin((M_PI/180.)*theta_out);
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ovec[0] = cos((M_PI/180.)*phi_out) * ovec[2];
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ovec[1] = sin((M_PI/180.)*phi_out) * ovec[2];
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ovec[2] = sqrt(1. - ovec[2]*ovec[2]);
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if (!isDSF)
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val *= ovec[2]; /* convert from BSDF to DSF */
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pos_from_vec(pos, ovec);
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dsf_grid[pos[0]][pos[1]].vsum += val;
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dsf_grid[pos[0]][pos[1]].nval++;
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}
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/* Compute radii for non-empty bins */
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/* (distance to furthest empty bin for which non-empty bin is the closest) */
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static void
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compute_radii(void)
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{
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unsigned int fill_grid[GRIDRES][GRIDRES];
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unsigned short fill_cnt[GRIDRES][GRIDRES];
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FVECT ovec0, ovec1;
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double ang2, lastang2;
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int r, i, j, jn, ii, jj, inear, jnear;
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r = GRIDRES/2; /* proceed in zig-zag */
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for (i = 0; i < GRIDRES; i++)
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for (jn = 0; jn < GRIDRES; jn++) {
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j = (i&1) ? jn : GRIDRES-1-jn;
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if (dsf_grid[i][j].nval) /* find empty grid pos. */
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continue;
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ovec_from_pos(ovec0, i, j);
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inear = jnear = -1; /* find nearest non-empty */
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lastang2 = M_PI*M_PI;
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for (ii = i-r; ii <= i+r; ii++) {
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if (ii < 0) continue;
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if (ii >= GRIDRES) break;
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for (jj = j-r; jj <= j+r; jj++) {
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if (jj < 0) continue;
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if (jj >= GRIDRES) break;
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if (!dsf_grid[ii][jj].nval)
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continue;
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ovec_from_pos(ovec1, ii, jj);
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ang2 = 2. - 2.*DOT(ovec0,ovec1);
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if (ang2 >= lastang2)
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continue;
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lastang2 = ang2;
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inear = ii; jnear = jj;
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}
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}
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if (inear < 0) {
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fprintf(stderr,
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"%s: Could not find non-empty neighbor!\n",
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progname);
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exit(1);
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}
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ang2 = sqrt(lastang2);
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r = ANG2R(ang2); /* record if > previous */
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if (r > dsf_grid[inear][jnear].crad)
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dsf_grid[inear][jnear].crad = r;
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/* next search radius */
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r = ang2*(2.*GRIDRES/M_PI) + 3;
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}
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/* blur radii over hemisphere */
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memset(fill_grid, 0, sizeof(fill_grid));
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memset(fill_cnt, 0, sizeof(fill_cnt));
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for (i = 0; i < GRIDRES; i++)
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for (j = 0; j < GRIDRES; j++) {
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if (!dsf_grid[i][j].crad)
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continue; /* missing distance */
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r = R2ANG(dsf_grid[i][j].crad)*(2.*RSCA*GRIDRES/M_PI);
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for (ii = i-r; ii <= i+r; ii++) {
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if (ii < 0) continue;
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if (ii >= GRIDRES) break;
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for (jj = j-r; jj <= j+r; jj++) {
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if (jj < 0) continue;
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if (jj >= GRIDRES) break;
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if ((ii-i)*(ii-i) + (jj-j)*(jj-j) > r*r)
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continue;
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fill_grid[ii][jj] += dsf_grid[i][j].crad;
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fill_cnt[ii][jj]++;
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}
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}
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}
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/* copy back blurred radii */
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for (i = 0; i < GRIDRES; i++)
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for (j = 0; j < GRIDRES; j++)
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if (fill_cnt[i][j])
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dsf_grid[i][j].crad = fill_grid[i][j]/fill_cnt[i][j];
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}
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/* Cull points for more uniform distribution, leave all nval 0 or 1 */
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static void
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cull_values(void)
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{
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FVECT ovec0, ovec1;
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double maxang, maxang2;
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int i, j, ii, jj, r;
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/* simple greedy algorithm */
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for (i = 0; i < GRIDRES; i++)
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for (j = 0; j < GRIDRES; j++) {
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if (!dsf_grid[i][j].nval)
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continue;
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if (!dsf_grid[i][j].crad)
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continue; /* shouldn't happen */
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ovec_from_pos(ovec0, i, j);
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maxang = 2.*R2ANG(dsf_grid[i][j].crad);
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if (maxang > ovec0[2]) /* clamp near horizon */
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maxang = ovec0[2];
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r = maxang*(2.*GRIDRES/M_PI) + 1;
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maxang2 = maxang*maxang;
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for (ii = i-r; ii <= i+r; ii++) {
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if (ii < 0) continue;
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if (ii >= GRIDRES) break;
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for (jj = j-r; jj <= j+r; jj++) {
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if (jj < 0) continue;
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if (jj >= GRIDRES) break;
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if (!dsf_grid[ii][jj].nval)
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continue;
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if ((ii == i) & (jj == j))
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continue; /* don't get self-absorbed */
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ovec_from_pos(ovec1, ii, jj);
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if (2. - 2.*DOT(ovec0,ovec1) >= maxang2)
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continue;
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/* absorb sum */
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dsf_grid[i][j].vsum += dsf_grid[ii][jj].vsum;
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dsf_grid[i][j].nval += dsf_grid[ii][jj].nval;
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/* keep value, though */
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dsf_grid[ii][jj].vsum /= (float)dsf_grid[ii][jj].nval;
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dsf_grid[ii][jj].nval = 0;
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}
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}
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}
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/* final averaging pass */
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for (i = 0; i < GRIDRES; i++)
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for (j = 0; j < GRIDRES; j++)
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if (dsf_grid[i][j].nval > 1) {
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dsf_grid[i][j].vsum /= (float)dsf_grid[i][j].nval;
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dsf_grid[i][j].nval = 1;
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}
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}
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/* Count up filled nodes and build RBF representation from current grid */
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RBFNODE *
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make_rbfrep(void)
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{
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int niter = 16;
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double lastVar, thisVar = 100.;
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int nn;
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RBFNODE *newnode;
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int i, j;
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/* compute RBF radii */
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compute_radii();
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/* coagulate lobes */
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cull_values();
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nn = 0; /* count selected bins */
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for (i = 0; i < GRIDRES; i++)
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for (j = 0; j < GRIDRES; j++)
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nn += dsf_grid[i][j].nval;
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/* allocate RBF array */
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newnode = (RBFNODE *)malloc(sizeof(RBFNODE) + sizeof(RBFVAL)*(nn-1));
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if (newnode == NULL) {
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fprintf(stderr, "%s: Out of memory in make_rbfrep()\n", progname);
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exit(1);
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}
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newnode->ord = -1;
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newnode->next = NULL;
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newnode->ejl = NULL;
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newnode->invec[2] = sin((M_PI/180.)*theta_in_deg);
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newnode->invec[0] = cos((M_PI/180.)*phi_in_deg)*newnode->invec[2];
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newnode->invec[1] = sin((M_PI/180.)*phi_in_deg)*newnode->invec[2];
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newnode->invec[2] = input_orient*sqrt(1. - newnode->invec[2]*newnode->invec[2]);
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newnode->vtotal = 0;
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newnode->nrbf = nn;
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nn = 0; /* fill RBF array */
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for (i = 0; i < GRIDRES; i++)
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for (j = 0; j < GRIDRES; j++)
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if (dsf_grid[i][j].nval) {
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newnode->rbfa[nn].peak = dsf_grid[i][j].vsum;
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newnode->rbfa[nn].crad = RSCA*dsf_grid[i][j].crad + .5;
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newnode->rbfa[nn].gx = i;
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newnode->rbfa[nn].gy = j;
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++nn;
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}
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/* iterate to improve interpolation accuracy */
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do {
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double dsum = 0, dsum2 = 0;
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nn = 0;
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for (i = 0; i < GRIDRES; i++)
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for (j = 0; j < GRIDRES; j++)
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if (dsf_grid[i][j].nval) {
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FVECT odir;
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double corr;
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ovec_from_pos(odir, i, j);
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newnode->rbfa[nn++].peak *= corr =
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dsf_grid[i][j].vsum /
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eval_rbfrep(newnode, odir);
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dsum += corr - 1.;
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dsum2 += (corr-1.)*(corr-1.);
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}
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lastVar = thisVar;
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thisVar = dsum2/(double)nn;
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#ifdef DEBUG
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fprintf(stderr, "Avg., RMS error: %.1f%% %.1f%%\n",
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100.*dsum/(double)nn,
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100.*sqrt(thisVar));
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#endif
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} while (--niter > 0 && lastVar-thisVar > 0.02*lastVar);
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nn = 0; /* compute sum for normalization */
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while (nn < newnode->nrbf)
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newnode->vtotal += rbf_volume(&newnode->rbfa[nn++]);
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insert_dsf(newnode);
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return(newnode);
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}
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