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...
bool	analyze_flow_field (struct flow_t *vectors, int count, float error_threshold, int n_iterations, int n_samples, int im_width, int im_height, float focal_length, struct linear_flow_fit_info *info)
	Analyze a flow field, retrieving information on relative velocities and rotations, etc. More...

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Data Structure Documentation

linear_flow_fit_info

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	rotation_X	Rotation around the X axis.
float	rotation_Y	Rotation around the Y axis.
float	rotation_Z	Rotation around the Z 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

analyze_flow_field()

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

Analyze a flow field, retrieving information on relative velocities and rotations, etc.

Parameters

[out]	outcome	If 0, there were too few vectors for a fit. If 1, the fit was successful.
[in]	vectors	The optical flow vectors
[in]	count	The number of optical flow vectors
[in]	error_threshold	Error used to determine inliers / outliers.
[in]	n_iterations	Number of RANSAC iterations.
[in]	n_samples	Number of samples used for a single fit (min. 5).
[in]	im_width	Image width in pixels
[in]	im_height	Image height in pixels
[in]	focal_length	Focal length in pixels
[out]	info	Contains all info extracted from the linear flow fit.

Definition at line 399 of file linear_flow_fit.c.

References N_PAR_TR_FIT.

Referenced by calc_fast9_lukas_kanade().

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analyze_linear_flow_field()

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]	outcome	If 0, there were too few vectors for a fit. If 1, the fit was successful.
[in]	vectors	The optical flow vectors
[in]	count	The number of optical flow vectors
[in]	error_threshold	Error used to determine inliers / outliers.
[in]	n_iterations	Number of RANSAC iterations.
[in]	n_samples	Number of samples used for a single fit (min. 3).
[in]	im_width	Image width in pixels
[in]	im_height	Image height in pixels
[out]	info	Contains all info extracted from the linear flow fit.

Definition at line 67 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, n_samples, 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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extract_information_from_parameters()

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_width	Width of image in pixels
[in]	im_height	Height of image in pixels
[out]	info	Contains all info extracted from the linear flow fit

Definition at line 321 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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fit_linear_flow_field()

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]	vectors	The optical flow vectors
[in]	count	The number of optical flow vectors
[in]	error_threshold	Error used to determine inliers / outliers.
[in]	n_iterations	Number of RANSAC iterations.
[in]	n_samples	Number 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 109 of file linear_flow_fit.c.

References A, 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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