/* trackcorr_c_loop is the main tracking subroutine that scans the 3D particle position
* data from rt_is.* files and the 2D particle positions in image space in _targets and
* constructs trajectories (links) of the particles in 3D in time.
* the basic concepts of the tracking procedure are from the following publication by
* Jochen Willneff: "A New Spatio-Temporal Matching Algorithm For 3D-Particle Tracking Velocimetry"
* https://www.mendeley.com/catalog/new-spatiotemporal-matching-algorithm-3dparticle-tracking-velocimetry/
* or http://e-collection.library.ethz.ch/view/eth:26978
* this method is an extension of the previously used tracking method described in details in
* Malik et al. 1993: "Particle tracking velocimetry in three-dimensional flows: Particle tracking"
* http://mnd.ly/2dCt3um
*
* Arguments:
* tracking_run *run_info pointer to the (sliding) frame dataset of 4 frames of particle positions
* and all the needed parameters underneath: control, volume, etc.
* integer step number or the frame number from the sequence
* Note: step is not really setting up the step to track, the buffer provided to the trackcoor_c_loop
* is already preset by 4 frames buf[0] to buf[3] and we track particles in buf[1], i.e. one "previous"
* one present and two future frames.
*
* Returns: function does not return an argument, the tracks are updated within the run_info dataset
*/
void trackcorr_c_loop (tracking_run *run_info, int step) {
/* sequence loop */
int j, h, mm, kk, in_volume = 0;
int philf[4][MAX_CANDS];
int count1 = 0, count2 = 0, count3 = 0, num_added = 0;
int quali = 0;
vec3d diff_pos, X[6]; /* 7 reference points used in the algorithm, TODO: check if can reuse some */
double angle, acc, angle0, acc0, dl;
double angle1, acc1;
vec2d v1[4], v2[4]; /* volume center projection on cameras */
double rr;
/* Shortcuts to inside current frame */
P *curr_path_inf, *ref_path_inf;
corres *curr_corres;
target **curr_targets;
int _ix; /* For use in any of the complex index expressions below */
int orig_parts; /* avoid infinite loop with particle addition set */
/* Shortcuts into the tracking_run struct */
Calibration **cal;
framebuf *fb;
track_par *tpar;
volume_par *vpar;
control_par *cpar;
foundpix *w, *wn;
count1 = 0; num_added = 0;
fb = run_info->fb;
cal = run_info->cal;
tpar = run_info->tpar;
vpar = run_info->vpar;
cpar = run_info->cpar;
curr_targets = fb->buf[1]->targets;
/* try to track correspondences from previous 0 - corp, variable h */
orig_parts = fb->buf[1]->num_parts;
for (h = 0; h < orig_parts; h++) {
for (j = 0; j < 6; j++) vec_init(X[j]);
curr_path_inf = &(fb->buf[1]->path_info[h]);
curr_corres = &(fb->buf[1]->correspond[h]);
curr_path_inf->inlist = 0;
/* 3D-position */
vec_copy(X[1], curr_path_inf->x);
/* use information from previous to locate new search position
and to calculate values for search area */
if (curr_path_inf->prev >= 0) {
ref_path_inf = &(fb->buf[0]->path_info[curr_path_inf->prev]);
vec_copy(X[0], ref_path_inf->x);
search_volume_center_moving(ref_path_inf->x, curr_path_inf->x, X[2]);
for (j = 0; j < fb->num_cams; j++) {
point_to_pixel (v1[j], X[2], cal[j], cpar);
}
} else {
vec_copy(X[2], X[1]);
for (j = 0; j < fb->num_cams; j++) {
if (curr_corres->p[j] == -1) {
point_to_pixel (v1[j], X[2], cal[j], cpar);
} else {
_ix = curr_corres->p[j];
v1[j][0] = curr_targets[j][_ix].x;
v1[j][1] = curr_targets[j][_ix].y;
}
}
}
/* calculate search cuboid and reproject it to the image space */
w = sorted_candidates_in_volume(X[2], v1, fb->buf[2], run_info);
if (w == NULL) continue;
/* Continue to find candidates for the candidates. */
count2++;
mm = 0;
while (w[mm].ftnr != TR_UNUSED) { /* counter1-loop */
/* search for found corr of current the corr in next
with predicted location */
/* found 3D-position */
ref_path_inf = &(fb->buf[2]->path_info[w[mm].ftnr]);
vec_copy(X[3], ref_path_inf->x);
if (curr_path_inf->prev >= 0) {
for (j = 0; j < 3; j++)
X[5][j] = 0.5*(5.0*X[3][j] - 4.0*X[1][j] + X[0][j]);
} else {
search_volume_center_moving(X[1], X[3], X[5]);
}
for (j = 0; j < fb->num_cams; j++) {
point_to_pixel (v1[j], X[5], cal[j], cpar);
}
/* end of search in pix */
wn = sorted_candidates_in_volume(X[5], v1, fb->buf[3], run_info);
if (wn != NULL) {
count3++;
kk = 0;
while (wn[kk].ftnr != TR_UNUSED) {
ref_path_inf = &(fb->buf[3]->path_info[wn[kk].ftnr]);
vec_copy(X[4], ref_path_inf->x);
vec_subt(X[4], X[3], diff_pos);
if ( pos3d_in_bounds(diff_pos, tpar)) {
angle_acc(X[3], X[4], X[5], &angle1, &acc1);
if (curr_path_inf->prev >= 0) {
angle_acc(X[1], X[2], X[3], &angle0, &acc0);
} else {
acc0 = acc1; angle0 = angle1;
}
acc = (acc0+acc1)/2; angle = (angle0+angle1)/2;
quali = wn[kk].freq+w[mm].freq;
if ((acc < tpar->dacc && angle < tpar->dangle) || \
(acc < tpar->dacc/10))
{
dl = (vec_diff_norm(X[1], X[3]) +
vec_diff_norm(X[4], X[3]) )/2;
rr = (dl/run_info->lmax + acc/tpar->dacc + \
angle/tpar->dangle)/(quali);
register_link_candidate(
curr_path_inf, rr, w[mm].ftnr);
}
}
kk++;
} /* End of searching 2nd-frame candidates. */
}
/* creating new particle position,
* reset img coord because of num_cams < 4
* fix distance of 3 pixels to define xl,xr,yu,yd instead of searchquader
* and search for unused candidates in next time step
*/
quali = assess_new_position(X[5], v2, philf, fb->buf[3], run_info);
/* quali >=2 means at least in two cameras
* we found a candidate
*/
if ( quali >= 2) {
in_volume = 0; //inside volume
dl = point_position(v2, cpar->num_cams, cpar->mm, cal, X[4]);
/* volume check */
if ( vpar->X_lay[0] < X[4][0] && X[4][0] < vpar->X_lay[1] &&
run_info->ymin < X[4][1] && X[4][1] < run_info->ymax &&
vpar->Zmin_lay[0] < X[4][2] && X[4][2] < vpar->Zmax_lay[1])
{
in_volume = 1;
}
vec_subt(X[3], X[4], diff_pos);
if ( in_volume == 1 && pos3d_in_bounds(diff_pos, tpar) ) {
angle_acc(X[3], X[4], X[5], &angle, &acc);
if ((acc < tpar->dacc && angle < tpar->dangle) || \
(acc < tpar->dacc/10))
{
dl = (vec_diff_norm(X[1], X[3]) +
vec_diff_norm(X[4], X[3]) )/2;
rr = (dl/run_info->lmax + acc/tpar->dacc + angle/tpar->dangle) /
(quali+w[mm].freq);
register_link_candidate(curr_path_inf, rr, w[mm].ftnr);
if (tpar->add) {
add_particle(fb->buf[3], X[4], philf);
num_added++;
}
}
}
in_volume = 0;
}
quali = 0;
/* end of creating new particle position */
/* *************************************************************** */
/* try to link if kk is not found/good enough and prev exist */
if ( curr_path_inf->inlist == 0 && curr_path_inf->prev >= 0 ) {
vec_subt(X[3], X[1], diff_pos);
if (pos3d_in_bounds(diff_pos, tpar)) {
angle_acc(X[1], X[2], X[3], &angle, &acc);
if ( (acc < tpar->dacc && angle < tpar->dangle) || \
(acc < tpar->dacc/10) )
{
quali = w[mm].freq;
dl = (vec_diff_norm(X[1], X[3]) +
vec_diff_norm(X[0], X[1]) )/2;
rr = (dl/run_info->lmax + acc/tpar->dacc + angle/tpar->dangle)/(quali);
register_link_candidate(curr_path_inf, rr, w[mm].ftnr);
}
}
}
free(wn);
mm++;
} /* end of loop over first-frame candidates. */
/* begin of inlist still zero */
if (tpar->add) {
if ( curr_path_inf->inlist == 0 && curr_path_inf->prev >= 0 ) {
quali = assess_new_position(X[2], v2, philf, fb->buf[2], run_info);
if (quali>=2) {
vec_copy(X[3], X[2]);
in_volume = 0;
dl = point_position(v2, fb->num_cams, cpar->mm, cal, X[3]);
/* in volume check */
if ( vpar->X_lay[0] < X[3][0] && X[3][0] < vpar->X_lay[1] &&
run_info->ymin < X[3][1] && X[3][1] < run_info->ymax &&
vpar->Zmin_lay[0] < X[3][2] &&
X[3][2] < vpar->Zmax_lay[1])
{
in_volume = 1;
}
vec_subt(X[2], X[3], diff_pos);
if ( in_volume == 1 && pos3d_in_bounds(diff_pos, tpar) ) {
angle_acc(X[1], X[2], X[3], &angle, &acc);
if ( (acc < tpar->dacc && angle < tpar->dangle) || \
(acc < tpar->dacc/10) )
{
dl = (vec_diff_norm(X[1], X[3]) +
vec_diff_norm(X[0], X[1]) )/2;
rr = (dl/run_info->lmax + acc/tpar->dacc + angle/tpar->dangle)/(quali);
register_link_candidate(curr_path_inf, rr, fb->buf[2]->num_parts);
add_particle(fb->buf[2], X[3], philf);
num_added++;
}
}
in_volume = 0;
} // if quali >= 2
}
}
/* end of inlist still zero */
/***********************************/
free(w);
} /* end of h-loop */
/* sort decis and give preliminary "finaldecis" */
for (h = 0; h < fb->buf[1]->num_parts; h++) {
curr_path_inf = &(fb->buf[1]->path_info[h]);
if(curr_path_inf->inlist > 0 ) {
sort(curr_path_inf->inlist, (float *) curr_path_inf->decis,
curr_path_inf->linkdecis);
curr_path_inf->finaldecis = curr_path_inf->decis[0];
curr_path_inf->next = curr_path_inf->linkdecis[0];
}
}
/* create links with decision check */
for (h = 0; h < fb->buf[1]->num_parts; h++) {
curr_path_inf = &(fb->buf[1]->path_info[h]);
if(curr_path_inf->inlist > 0 ) {
ref_path_inf = &(fb->buf[2]->path_info[curr_path_inf->next]);
if (ref_path_inf->prev == PREV_NONE) {
/* best choice wasn't used yet, so link is created */
ref_path_inf->prev = h;
} else {
/* best choice was already used by mega[2][mega[1][h].next].prev */
/* check which is the better choice */
if ( fb->buf[1]->path_info[ref_path_inf->prev].finaldecis > \
curr_path_inf->finaldecis)
{
/* remove link with prev */
fb->buf[1]->path_info[ref_path_inf->prev].next = NEXT_NONE;
ref_path_inf->prev = h;
} else {
curr_path_inf->next = NEXT_NONE;
}
}
}
if (curr_path_inf->next != NEXT_NONE ) count1++;
}
/* end of creation of links with decision check */
printf ("step: %d, curr: %d, next: %d, links: %d, lost: %d, add: %d\n",
step, fb->buf[1]->num_parts, fb->buf[2]->num_parts, count1,
fb->buf[1]->num_parts - count1, num_added);
/* for the average of particles and links */
run_info->npart = run_info->npart + fb->buf[1]->num_parts;
run_info->nlinks = run_info->nlinks + count1;
fb_next(fb);
fb_write_frame_from_start(fb, step);
if(step < run_info->seq_par->last - 2) {
fb_read_frame_at_end(fb, step + 3, 0);
}
} /* end of sequence loop */
/* track backwards */
double trackback_c (tracking_run *run_info)
{
int i, j, h, in_volume = 0;
int step;
int philf[4][MAX_CANDS];
int count1 = 0, count2 = 0, num_added = 0;
int quali = 0;
double angle, acc, dl;
vec3d diff_pos, X[6]; /* 6 reference points used in the algorithm */
vec2d n[4], v2[4]; // replaces xn,yn, x2[4], y2[4],
double rr, Ymin = 0, Ymax = 0;
double npart = 0, nlinks = 0;
foundpix *w;
sequence_par *seq_par;
track_par *tpar;
volume_par *vpar;
control_par *cpar;
framebuf *fb;
Calibration **cal;
/* Shortcuts to inside current frame */
P *curr_path_inf, *ref_path_inf;
/* shortcuts */
cal = run_info->cal;
seq_par = run_info->seq_par;
tpar = run_info->tpar;
vpar = run_info->vpar;
cpar = run_info->cpar;
fb = run_info->fb;
/* Prime the buffer with first frames */
for (step = seq_par->last; step > seq_par->last - 4; step--) {
fb_read_frame_at_end(fb, step, 1);
fb_next(fb);
}
fb_prev(fb);
/* sequence loop */
for (step = seq_par->last - 1; step > seq_par->first; step--) {
printf ("Time step: %d, seqnr: %d:\n",
step - seq_par->first, step);
for (h = 0; h < fb->buf[1]->num_parts; h++) {
curr_path_inf = &(fb->buf[1]->path_info[h]);
/* We try to find link only if the forward search failed to. */
if ((curr_path_inf->next < 0) || (curr_path_inf->prev != -1)) continue;
for (j = 0; j < 6; j++) vec_init(X[j]);
curr_path_inf->inlist = 0;
/* 3D-position of current particle */
vec_copy(X[1], curr_path_inf->x);
/* use information from previous to locate new search position
and to calculate values for search area */
ref_path_inf = &(fb->buf[0]->path_info[curr_path_inf->next]);
vec_copy(X[0], ref_path_inf->x);
search_volume_center_moving(ref_path_inf->x, curr_path_inf->x, X[2]);
for (j = 0; j < fb->num_cams; j++) {
point_to_pixel (n[j], X[2], cal[j], cpar);
}
/* calculate searchquader and reprojection in image space */
w = sorted_candidates_in_volume(X[2], n, fb->buf[2], run_info);
if (w != NULL) {
count2++;
i = 0;
while (w[i].ftnr != TR_UNUSED) {
ref_path_inf = &(fb->buf[2]->path_info[w[i].ftnr]);
vec_copy(X[3], ref_path_inf->x);
vec_subt(X[1], X[3], diff_pos);
if (pos3d_in_bounds(diff_pos, tpar)) {
angle_acc(X[1], X[2], X[3], &angle, &acc);
/* *********************check link *****************************/
if ((acc < tpar->dacc && angle < tpar->dangle) || \
(acc < tpar->dacc/10))
{
dl = (vec_diff_norm(X[1], X[3]) +
vec_diff_norm(X[0], X[1]) )/2;
quali = w[i].freq;
rr = (dl/run_info->lmax + acc/tpar->dacc + \
angle/tpar->dangle)/quali;
register_link_candidate(curr_path_inf, rr, w[i].ftnr);
}
}
i++;
}
}
free(w);
/* if old wasn't found try to create new particle position from rest */
if (tpar->add) {
if ( curr_path_inf->inlist == 0) {
quali = assess_new_position(X[2], v2, philf, fb->buf[2], run_info);
if (quali>=2) {
//vec_copy(X[3], X[2]);
in_volume = 0;
point_position(v2, fb->num_cams, cpar->mm, cal, X[3]);
/* volume check */
if ( vpar->X_lay[0] < X[3][0] && X[3][0] < vpar->X_lay[1] &&
Ymin < X[3][1] && X[3][1] < Ymax &&
vpar->Zmin_lay[0] < X[3][2] && X[3][2] < vpar->Zmax_lay[1])
{in_volume = 1;}
vec_subt(X[1], X[3], diff_pos);
if (in_volume == 1 && pos3d_in_bounds(diff_pos, tpar)) {
angle_acc(X[1], X[2], X[3], &angle, &acc);
if ( (acc<tpar->dacc && angle<tpar->dangle) || \
(acc<tpar->dacc/10) )
{
dl = (vec_diff_norm(X[1], X[3]) +
vec_diff_norm(X[0], X[1]) )/2;
rr = (dl/run_info->lmax+acc/tpar->dacc + angle/tpar->dangle)/(quali);
register_link_candidate(curr_path_inf, rr, fb->buf[2]->num_parts);
add_particle(fb->buf[2], X[3], philf);
}
}
in_volume = 0;
}
}
} /* end of if old wasn't found try to create new particle position from rest */
} /* end of h-loop */
for (h = 0; h < fb->buf[1]->num_parts; h++) {
curr_path_inf = &(fb->buf[1]->path_info[h]);
if(curr_path_inf->inlist > 0 ) {
sort(curr_path_inf->inlist, (float *)curr_path_inf->decis,
curr_path_inf->linkdecis);
}
}
/* create links with decision check */
count1 = 0; num_added = 0;
for (h = 0; h < fb->buf[1]->num_parts; h++) {
curr_path_inf = &(fb->buf[1]->path_info[h]);
if (curr_path_inf->inlist > 0 ) {
/* if old/new and unused prev == -1 and next == -2 link is created */
ref_path_inf = &(fb->buf[2]->path_info[curr_path_inf->linkdecis[0]]);
if ( ref_path_inf->prev == PREV_NONE && \
ref_path_inf->next == NEXT_NONE )
{
curr_path_inf->finaldecis = curr_path_inf->decis[0];
curr_path_inf->prev = curr_path_inf->linkdecis[0];
fb->buf[2]->path_info[curr_path_inf->prev].next = h;
num_added++;
}
/* old which link to prev has to be checked */
if ((ref_path_inf->prev != PREV_NONE) && \
(ref_path_inf->next == NEXT_NONE) )
{
vec_copy(X[0], fb->buf[0]->path_info[curr_path_inf->next].x);
vec_copy(X[1], curr_path_inf->x);
vec_copy(X[3], ref_path_inf->x);
vec_copy(X[4], fb->buf[3]->path_info[ref_path_inf->prev].x);
for (j = 0; j < 3; j++)
X[5][j] = 0.5*(5.0*X[3][j] - 4.0*X[1][j] + X[0][j]);
angle_acc(X[3], X[4], X[5], &angle, &acc);
if ( (acc<tpar->dacc && angle<tpar->dangle) || (acc<tpar->dacc/10) ) {
curr_path_inf->finaldecis = curr_path_inf->decis[0];
curr_path_inf->prev = curr_path_inf->linkdecis[0];
fb->buf[2]->path_info[curr_path_inf->prev].next = h;
num_added++;
}
}
}
if (curr_path_inf->prev != PREV_NONE ) count1++;
} /* end of creation of links with decision check */
printf ("step: %d, curr: %d, next: %d, links: %d, lost: %d, add: %d",
step, fb->buf[1]->num_parts, fb->buf[2]->num_parts, count1,
fb->buf[1]->num_parts - count1, num_added);
/* for the average of particles and links */
npart = npart + fb->buf[1]->num_parts;
nlinks = nlinks + count1;
fb_next(fb);
fb_write_frame_from_start(fb, step);
if(step > seq_par->first + 2) { fb_read_frame_at_end(fb, step - 3, 1); }
} /* end of sequence loop */
/* average of all steps */
npart /= (seq_par->last - seq_par->first - 1);
nlinks /= (seq_par->last - seq_par->first - 1);
printf ("Average over sequence, particles: %5.1f, links: %5.1f, lost: %5.1f\n",
npart, nlinks, npart-nlinks);
fb_next(fb);
fb_write_frame_from_start(fb, step);
return nlinks;
}
