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#ifndef lint |
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static const char RCSid[] = "$Id: bsdfrbf.c,v 2.7 2013/09/25 17:42:45 greg Exp $"; |
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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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|
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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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|
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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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#ifndef MAXFRAC |
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#define MAXFRAC 0.5 /* maximum contribution to neighbor */ |
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#endif |
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#ifndef NNEIGH |
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#define NNEIGH 10 /* number of neighbors to consider */ |
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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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|
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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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|
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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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|
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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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|
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if (val <= 0) /* truncate to zero */ |
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val = 0; |
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else if (!isDSF) |
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val *= ovec[2]; /* convert from BSDF to DSF */ |
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|
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/* update BSDF histogram */ |
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if (val < BSDF2BIG*ovec[2] && val > BSDF2SML*ovec[2]) |
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++bsdf_hist[histndx(val/ovec[2])]; |
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|
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pos_from_vec(pos, ovec); |
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|
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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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|
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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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|
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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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|
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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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|
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/* Compute minimum BSDF from histogram and clear it */ |
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static void |
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comp_bsdf_min() |
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{ |
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int cnt; |
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int i, target; |
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|
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cnt = 0; |
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for (i = HISTLEN; i--; ) |
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cnt += bsdf_hist[i]; |
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if (!cnt) { /* shouldn't happen */ |
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bsdf_min = 0; |
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return; |
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} |
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target = cnt/100; /* ignore bottom 1% */ |
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cnt = 0; |
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for (i = 0; cnt <= target; i++) |
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cnt += bsdf_hist[i]; |
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bsdf_min = histval(i-1); |
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memset(bsdf_hist, 0, sizeof(bsdf_hist)); |
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} |
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|
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/* Find n nearest sub-sampled neighbors to the given grid position */ |
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static int |
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get_neighbors(int neigh[][2], int n, const int i, const int j) |
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{ |
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int k = 0; |
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int r; |
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/* search concentric squares */ |
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for (r = 1; r < GRIDRES; r++) { |
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int ii, jj; |
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for (ii = i-r; ii <= i+r; ii++) { |
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int jstep = 1; |
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if (ii < 0) continue; |
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if (ii >= GRIDRES) break; |
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if ((i-r < ii) & (ii < i+r)) |
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jstep = r<<1; |
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for (jj = j-r; jj <= j+r; jj += jstep) { |
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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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neigh[k][0] = ii; |
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neigh[k][1] = jj; |
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if (++k >= n) |
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return(n); |
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} |
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} |
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} |
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} |
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return(k); |
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} |
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|
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/* Adjust coded radius for the given grid position based on neighborhood */ |
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static int |
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adj_coded_radius(const int i, const int j) |
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{ |
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const double rad0 = R2ANG(dsf_grid[i][j].crad); |
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double currad = RSCA * rad0; |
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int neigh[NNEIGH][2]; |
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int n; |
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FVECT our_dir; |
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|
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ovec_from_pos(our_dir, i, j); |
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n = get_neighbors(neigh, NNEIGH, i, j); |
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while (n--) { |
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FVECT their_dir; |
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double max_ratio, rad_ok2; |
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/* check our value at neighbor */ |
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ovec_from_pos(their_dir, neigh[n][0], neigh[n][1]); |
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max_ratio = MAXFRAC * dsf_grid[neigh[n][0]][neigh[n][1]].vsum |
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/ dsf_grid[i][j].vsum; |
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if (max_ratio >= 1) |
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continue; |
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rad_ok2 = (DOT(their_dir,our_dir) - 1.)/log(max_ratio); |
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if (rad_ok2 >= currad*currad) |
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continue; /* value fraction OK */ |
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currad = sqrt(rad_ok2); /* else reduce lobe radius */ |
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if (currad <= rad0) /* limit how small we'll go */ |
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return(dsf_grid[i][j].crad); |
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} |
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return(ANG2R(currad)); /* encode selected radius */ |
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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 * |
| 285 |
make_rbfrep(void) |
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{ |
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int niter = 16; |
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double lastVar, thisVar = 100.; |
| 289 |
int nn; |
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RBFNODE *newnode; |
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RBFVAL *itera; |
| 292 |
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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/* compute minimum BSDF */ |
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comp_bsdf_min(); |
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/* allocate RBF array */ |
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newnode = (RBFNODE *)malloc(sizeof(RBFNODE) + sizeof(RBFVAL)*(nn-1)); |
| 305 |
if (newnode == NULL) |
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goto memerr; |
| 307 |
newnode->ord = -1; |
| 308 |
newnode->next = NULL; |
| 309 |
newnode->ejl = NULL; |
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newnode->invec[2] = sin((M_PI/180.)*theta_in_deg); |
| 311 |
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]; |
| 313 |
newnode->invec[2] = input_orient*sqrt(1. - newnode->invec[2]*newnode->invec[2]); |
| 314 |
newnode->vtotal = 0; |
| 315 |
newnode->nrbf = nn; |
| 316 |
nn = 0; /* fill RBF array */ |
| 317 |
for (i = 0; i < GRIDRES; i++) |
| 318 |
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; |
| 321 |
newnode->rbfa[nn].crad = adj_coded_radius(i, j); |
| 322 |
newnode->rbfa[nn].gx = i; |
| 323 |
newnode->rbfa[nn].gy = j; |
| 324 |
++nn; |
| 325 |
} |
| 326 |
/* iterate to improve interpolation accuracy */ |
| 327 |
itera = (RBFVAL *)malloc(sizeof(RBFVAL)*newnode->nrbf); |
| 328 |
if (itera == NULL) |
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goto memerr; |
| 330 |
memcpy(itera, newnode->rbfa, sizeof(RBFVAL)*newnode->nrbf); |
| 331 |
do { |
| 332 |
double dsum = 0, dsum2 = 0; |
| 333 |
nn = 0; |
| 334 |
for (i = 0; i < GRIDRES; i++) |
| 335 |
for (j = 0; j < GRIDRES; j++) |
| 336 |
if (dsf_grid[i][j].nval) { |
| 337 |
FVECT odir; |
| 338 |
double corr; |
| 339 |
ovec_from_pos(odir, i, j); |
| 340 |
itera[nn++].peak *= corr = |
| 341 |
dsf_grid[i][j].vsum / |
| 342 |
eval_rbfrep(newnode, odir); |
| 343 |
dsum += 1. - corr; |
| 344 |
dsum2 += (1.-corr)*(1.-corr); |
| 345 |
} |
| 346 |
memcpy(newnode->rbfa, itera, sizeof(RBFVAL)*newnode->nrbf); |
| 347 |
lastVar = thisVar; |
| 348 |
thisVar = dsum2/(double)nn; |
| 349 |
#ifdef DEBUG |
| 350 |
fprintf(stderr, "Avg., RMS error: %.1f%% %.1f%%\n", |
| 351 |
100.*dsum/(double)nn, |
| 352 |
100.*sqrt(thisVar)); |
| 353 |
#endif |
| 354 |
} while (--niter > 0 && lastVar-thisVar > 0.02*lastVar); |
| 355 |
|
| 356 |
free(itera); |
| 357 |
nn = 0; /* compute sum for normalization */ |
| 358 |
while (nn < newnode->nrbf) |
| 359 |
newnode->vtotal += rbf_volume(&newnode->rbfa[nn++]); |
| 360 |
#ifdef DEBUG |
| 361 |
fprintf(stderr, "Integrated DSF at (%.1f,%.1f) deg. is %.2f\n", |
| 362 |
get_theta180(newnode->invec), get_phi360(newnode->invec), |
| 363 |
newnode->vtotal); |
| 364 |
#endif |
| 365 |
insert_dsf(newnode); |
| 366 |
|
| 367 |
return(newnode); |
| 368 |
memerr: |
| 369 |
fprintf(stderr, "%s: Out of memory in make_rbfrep()\n", progname); |
| 370 |
exit(1); |
| 371 |
} |
