### astGetRegionPoints

Returns the positions that define the given Region

#### Description:

This function returns the axis values at the points that define the supplied Region. The particular meaning of these points will depend on the type of class supplied, as listed below under " Applicability:" .

#### Synopsis

void astGetRegionPoints( AstRegion $\ast$this, int maxpoint, int maxcoord, int $\ast$npoint, double $\ast$points )

#### Parameters:

##### this
Pointer to the Region.
##### maxpoint
If zero, the number of points needed to define the Region is returned in " $\ast$npoint" , but no axis values are returned and all other parameters are ignored. If not zero, the supplied value should be the length of the second dimension of the " points" array. An error is reported if the number of points needed to define the Region exceeds this number.
##### maxcoord
The length of the first dimension of the " points" array. An error is reported if the number of axes in the supplied Region exceeds this number.
##### npoint
A pointer to an integer in which to return the number of points defining the Region.
##### points
The address of the first element in a 2-dimensional array of shape " [maxcoord][maxpoint]" , in which to return the coordinate values at the positions that define the Region. These are stored such that the value of coordinate number " coord" for point number " point" is found in element " points[coord][point]" .

#### Applicability

##### Region
All Regions have this attribute.
##### Box
The first returned position is the Box centre, and the second is a Box corner.
##### Circle
The first returned position is the Circle centre, and the second is a point on the circumference.
##### CmpRegion
Returns a value of zero for " $\ast$npoint" and leaves the supplied array contents unchanged. To find the points defining a CmpRegion, use this method on the component Regions, which can be accessed by invoking astDecompose on the CmpRegion.
##### Ellipse
The first returned position is the Ellipse centre. The second is the end of one of the axes of the ellipse. The third is some other point on the circumference of the ellipse, distinct from the second point.
##### Interval
The first point corresponds to the lower bounds position, and the second point corresponds to the upper bounds position. These are reversed to indicate an extcluded interval rather than an included interval. See the Interval constructor for more information.
##### NullRegion
Returns a value of zero for " $\ast$npoint" and leaves the supplied array contents unchanged.
##### PointList
The positions returned are those that were supplied when the PointList was constructed.
##### Polygon
The positions returned are the vertex positions that were supplied when the Polygon was constructed.
##### Prism
Returns a value of zero for " $\ast$npoint" and leaves the supplied array contents unchanged. To find the points defining a Prism, use this method on the component Regions, which can be accessed by invoking astDecompose on the CmpRegion.

#### Notes:

• If the coordinate system represented by the Region has been changed since it was first created, the returned axis values refer to the new (changed) coordinate system, rather than the original coordinate system. Note however that if the transformation from original to new coordinate system is non-linear, the shape within the new coordinate system may be distorted, and so may not match that implied by the name of the Region subclass (Circle, Box, etc).