#include <gsl/gsl_vector.h>
#include <gsl/gsl_interp.h>

Classes
struct	bt_spline
Enumerations
enum	bt_spline_mode { BT_SPLINE_MODE_ARCLEN, BT_SPLINE_MODE_EXTERNAL }
Functions
int	bt_spline_create (struct bt_spline *splineptr, const gsl_vector start, enum bt_spline_mode mode)
int	bt_spline_add (struct bt_spline spline, const gsl_vector vec, double s)
int	bt_spline_init (struct bt_spline spline, gsl_vector start, gsl_vector *direction)
int	bt_spline_destroy (struct bt_spline *spline)
int	bt_spline_get (struct bt_spline spline, gsl_vector result, double s)

Detailed Description

Definition of bt_spline, an n-dimensional vector interpolator.

Author:: Christopher Dellin

Date:: 2008-2009

This file is part of libbarrett.

This version of libbarrett is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This version of libbarrett is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this version of libbarrett. If not, see <http://www.gnu.org/licenses/>.

Barrett Technology Inc. 73 Chapel Street Newton, MA 02458

Introduction

A bt_spline is an abstraction over a set of GSL interpolators, one for each dimension of the spline's space. Points can be added to the spline as vectors, and the spline can then be interpolated over in a control loop. The spline can be parameterized by arclength or by an external parameter.

Enumeration Type Documentation

enum bt_spline_mode

A bt_spline has two different parameterization modes, arclen and external.

In BT_SPLINE_MODE_ARCLEN, the spline calculates the parameter s itself once it is initialized, based on the linear distance between the points. The resulting length is then available in the bt_spline::length variable. In this mode the s parameter in the bt_spline_add() function is ignored.

In BT_SPLINE_MODE_EXTERNAL, an external parameter is used. This value is saved along with each point through the s parameter of bt_spline_add(). The values start at zero when the starting point is added, and the subsequent values used must be monotonically increasing as the points are added. This mode is most often used with elapsed time serving as the external parameter.

Function Documentation

int bt_spline_add	(	struct bt_spline *	spline,
		const gsl_vector *	vec,
		double	s
	)

Add a point to a bt_spline.

This function is called iteratively once a bt_spline has been created to add points to the end of the spline. If the mode is BT_SPLINE_MODE_EXTERNAL, care must be take to ensure that the parameter s is monotonically increasing. If the mode is BT_SPLINE_MODE_ARCLEN, the s parameter is ignored.

Parameters:

[in]	spline	The bt_spline object to which to add the point
[in]	vec	The point to add
[in]	s	The values of the external parameter at this point

Return values:

0 Success

int bt_spline_create	(	struct bt_spline **	splineptr,
		const gsl_vector *	start,
		enum bt_spline_mode	mode
	)

Create a bt_spline object from a given start location.

This function creates a new bt_spline object, with the given vector as its starting point.

Parameters:

[out]	splineptr	The bt_spline object on success, or 0 on failure
[in]	start	Starting point
[in]	mode	Spline mode; either arclen or external.

Return values:

0 Success

This file is part of libbarrett.

This version of libbarrett is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This version of libbarrett is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this version of libbarrett. If not, see <http://www.gnu.org/licenses/>.

Barrett Technology Inc. 73 Chapel Street Newton, MA 02458

int bt_spline_destroy ( struct bt_spline * spline )

Destroy a bt_spline object.

This function destroys a bt_spline object created by bt_spline_create().

Parameters:

[in] spline The bt_spline object to destroy

Return values:

0 Success

int bt_spline_get	(	struct bt_spline *	spline,
		gsl_vector *	result,
		double	s
	)

Retrieve the interpolated vector at a given parameter value.

This function is designed to be called in a control loop to retrieve the interpolated vector at the paramater value s.

Parameters:

[in]	spline	The bt_spline object to use
[in]	result	The vector at the given paramter value
[in]	s	The parameter value to use

Return values:

0 Success

int bt_spline_init	(	struct bt_spline *	spline,
		gsl_vector *	start,
		gsl_vector *	direction
	)

Initialize the bt_spline after adding all points.

Once points are added to the spline using bt_spline_add(), the spline is initialized. This will create the interpolating objects for each dimension. If the start argument is passed, the original starting point given in bt_spline_create() will be replaced before any calculations take place. If the direction argument is passed, the initial slopes to each interpolator will be proportional to the normalized direction vector's values.

Note:: The direction vector, if passed and non-zero, will be normalized in place.

Parameters:

[in]	spline	The bt_spline object to initialize
[in]	start	A vector to replace the original start vector with, or 0 to skip this step
[in]	direction	A vector to use as the direction of the new spline

Return values:

0 Success

Classes

Enumerations

Functions

Detailed Description

Introduction

Enumeration Type Documentation

Function Documentation