Paparazzi UAS  v5.15_devel-110-g5cf27ee
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linear_flow_fit.h File Reference
#include "lib/vision/image.h"
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Data Structures

struct  linear_flow_fit_info
 

Functions

bool analyze_linear_flow_field (struct flow_t *vectors, int count, float error_threshold, int n_iterations, int n_samples, int im_width, int im_height, struct linear_flow_fit_info *info)
 Analyze a linear flow field, retrieving information such as divergence, surface roughness, focus of expansion, etc. More...
 
void fit_linear_flow_field (struct flow_t *vectors, int count, float error_threshold, int n_iterations, int n_samples, float *parameters_u, float *parameters_v, float *fit_error, float *min_error_u, float *min_error_v, int *n_inliers_u, int *n_inliers_v)
 Analyze a linear flow field, retrieving information such as divergence, surface roughness, focus of expansion, etc. More...
 
void extract_information_from_parameters (float *parameters_u, float *parameters_v, int im_width, int im_height, struct linear_flow_fit_info *info)
 Extract information from the parameters that were fit to the optical flow field. More...
 

Data Structure Documentation

struct linear_flow_fit_info

Definition at line 40 of file linear_flow_fit.h.

Data Fields
float divergence Basically, relative_velocity_z. Actual divergence of a 2D flow field is 2 * relative_velocity_z.
float fit_error Error of the fit (same as surface roughness)
float focus_of_expansion_x Image x-coordinate of the focus of expansion (contraction)
float focus_of_expansion_y Image y-coordinate of the focus of expansion (contraction)
int n_inliers_u Number of inliers in the horizontal flow fit.
int n_inliers_v Number of inliers in the vertical flow fit.
float relative_velocity_x Relative velocity in x-direction, i.e., vx / z, where z is the depth in direction of the camera's principal axis.
float relative_velocity_y Relative velocity in y-direction, i.e., vy / z, where z is the depth in direction of the camera's principal axis.
float relative_velocity_z Relative velocity in z-direction, i.e., vz / z, where z is the depth in direction of the camera's principal axis.
float slope_x Slope of the surface in x-direction - given sufficient lateral motion.
float slope_y Slope of the surface in y-direction - given sufficient lateral motion.
float surface_roughness The error of the linear fit is a measure of surface roughness.
float time_to_contact Basically, 1 / relative_velocity_z.

Function Documentation

bool analyze_linear_flow_field ( struct flow_t vectors,
int  count,
float  error_threshold,
int  n_iterations,
int  n_samples,
int  im_width,
int  im_height,
struct linear_flow_fit_info info 
)

Analyze a linear flow field, retrieving information such as divergence, surface roughness, focus of expansion, etc.

Parameters
[out]outcomeIf 0, there were too few vectors for a fit. If 1, the fit was successful.
[in]vectorsThe optical flow vectors
[in]countThe number of optical flow vectors
[in]error_thresholdError used to determine inliers / outliers.
[in]n_iterationsNumber of RANSAC iterations.
[in]n_samplesNumber of samples used for a single fit (min. 3).
[in]im_widthImage width in pixels
[in]im_heightImage height in pixels
[out]infoContains all info extracted from the linear flow fit.

Definition at line 63 of file linear_flow_fit.c.

References linear_flow_fit_info::divergence, E, extract_information_from_parameters(), linear_flow_fit_info::fit_error, fit_linear_flow_field(), MIN_SAMPLES_FIT, linear_flow_fit_info::n_inliers_u, linear_flow_fit_info::n_inliers_v, linear_flow_fit_info::relative_velocity_z, linear_flow_fit_info::surface_roughness, and linear_flow_fit_info::time_to_contact.

Referenced by calc_fast9_lukas_kanade().

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void extract_information_from_parameters ( float *  parameters_u,
float *  parameters_v,
int  im_width,
int  im_height,
struct linear_flow_fit_info info 
)

Extract information from the parameters that were fit to the optical flow field.

Parameters
[in]parameters_u*Parameters of the horizontal flow field
[in]parameters_v*Parameters of the vertical flow field
[in]im_widthWidth of image in pixels
[in]im_heightHeight of image in pixels
[out]infoContains all info extracted from the linear flow fit

Definition at line 313 of file linear_flow_fit.c.

References E, linear_flow_fit_info::focus_of_expansion_x, linear_flow_fit_info::focus_of_expansion_y, linear_flow_fit_info::relative_velocity_x, linear_flow_fit_info::relative_velocity_y, linear_flow_fit_info::relative_velocity_z, linear_flow_fit_info::slope_x, and linear_flow_fit_info::slope_y.

Referenced by analyze_linear_flow_field().

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void fit_linear_flow_field ( struct flow_t vectors,
int  count,
float  error_threshold,
int  n_iterations,
int  n_samples,
float *  parameters_u,
float *  parameters_v,
float *  fit_error,
float *  min_error_u,
float *  min_error_v,
int *  n_inliers_u,
int *  n_inliers_v 
)

Analyze a linear flow field, retrieving information such as divergence, surface roughness, focus of expansion, etc.

Parameters
[in]vectorsThe optical flow vectors
[in]countThe number of optical flow vectors
[in]error_thresholdError used to determine inliers / outliers.
[in]n_iterationsNumber of RANSAC iterations.
[in]n_samplesNumber of samples used for a single fit (min. 3).
[out]parameters_u*Parameters of the horizontal flow field
[out]parameters_v*Parameters of the vertical flow field
[out]fit_error*Total error of the finally selected fit
[out]min_error_u*Error fit horizontal flow field
[out]min_error_v*Error fit vertical flow field
[out]n_inliers_u*Number of inliers in the horizontal flow fit.
[out]n_inliers_v*Number of inliers in the vertical flow fit.

Definition at line 103 of file linear_flow_fit.c.

References A, AA, MAKE_MATRIX_PTR, MAT_MUL, MAT_SUB, MIN_SAMPLES_FIT, n_samples, p, flow_t::pos, pprz_svd_float(), pprz_svd_solve_float(), and point_t::y.

Referenced by analyze_linear_flow_field().

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