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#ifndef lint |
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static const char RCSid[] = "$Id: bsdfrbf.c,v 2.4 2013/03/20 01:00:22 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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/* 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 (!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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/* 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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RBFVAL *itera; |
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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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/* 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)); |
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if (newnode == NULL) |
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goto memerr; |
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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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itera = (RBFVAL *)malloc(sizeof(RBFVAL)*newnode->nrbf); |
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if (itera == NULL) |
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goto memerr; |
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memcpy(itera, newnode->rbfa, sizeof(RBFVAL)*newnode->nrbf); |
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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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itera[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 += 1. - corr; |
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dsum2 += (1.-corr)*(1.-corr); |
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} |
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memcpy(newnode->rbfa, itera, sizeof(RBFVAL)*newnode->nrbf); |
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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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|
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free(itera); |
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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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#ifdef DEBUG |
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fprintf(stderr, "Integrated DSF at (%.1f,%.1f) deg. is %.2f\n", |
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get_theta180(newnode->invec), get_phi360(newnode->invec), |
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newnode->vtotal); |
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#endif |
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insert_dsf(newnode); |
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|
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return(newnode); |
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memerr: |
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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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} |
