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astResolve
-
Resolve a vector into two orthogonal components
- Description:
This function resolves a vector into two perpendicular components.
The vector from point 1 to point 2 is used as the basis vector.
The vector from point 1 to point 3 is resolved into components
parallel and perpendicular to this basis vector. The lengths of the
two components are returned, together with the position of closest
aproach of the basis vector to point 3.
- Synopsis:
void astResolve( AstFrame *this, const double point1[],
const double point2[], const double point3[],
double point4[], double *d1, double *d2 );
- Parameters:
-
this
-
Pointer to the Frame.
-
point1
-
An array of double, with one element for each Frame axis
(Naxes attribute). This marks the start of the basis vector,
and of the vector to be resolved.
-
point2
-
An array of double, with one element for each Frame axis
(Naxes attribute). This marks the end of the basis vector.
-
point3
-
An array of double, with one element for each Frame axis
(Naxes attribute). This marks the end of the vector to be
resolved.
-
point4
-
An array of double, with one element for each Frame axis
in which the coordinates of the point of closest approach of the
basis vector to point 3 will be returned.
-
d1
-
The address of a location at which to return the distance from
point 1 to point 4 (that is, the length of the component parallel
to the basis vector). Positive values are in the same sense as
movement from point 1 to point 2.
-
d2
-
The address of a location at which to return the distance from
point 4 to point 3 (that is, the length of the component
perpendicular to the basis vector). The value is always positive.
- Notes:
-
Each vector used in this function is the path of
shortest distance between two points, as defined by the
astDistance function.
-
This function will return "bad" coordinate values (AST__BAD)
if any of the input coordinates has this value, or if the required
output values are undefined.
Next: astSet - Set attribute values for an Object
Up: AST Function Descriptions
Previous: astResample<X> - Resample a region of a data grid
AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 211
R.F. Warren-Smith & D.S. Berry
30th April 2003
E-mail:ussc@star.rl.ac.uk
Copyright (C) 2003 Central Laboratory of the Research Councils