region: Use astNormPoints to avoid longitude jumps in region meshes

ast.news

@@ -26,6 +26,10 @@ system. The most common usage will be to modify vectors of sky position
 in such a way as to avoid sudden jumps of 360 degrees in longitude within
 groups of points that span the longitude origin.
 
+- The mesh of points returned by astGetRegionMesh and astShowMesh are now
+normalised to avoid discontinuities in celestial longitude. This uses the
+new astNormPoints methid described in the previous item.
+
 - A bug has been fixed in the KeyMap class that caused astMapGet1<X>
 functions to return a vector length of 1 for KeyMap entries with an
 undefined value. A vector length of zero is now returned in such cases.

src/frame.c

@@ -8204,15 +8204,15 @@ static AstPointSet *NormalPoints( AstFrame *this, AstPointSet *in, int contig,
       for ( point = 0; point < npoint; point++ ) {
 
 /* Copy the axis values at the current point into the buffer. */
-         for ( coord = 0; coord < ncoord_in; coord++ ) {
+         for ( coord = 0; coord < naxes; coord++ ) {
             buf[ coord ] = ptr_in[ coord ][ point ];
          }
 
 /* Normalise the values stored in the buffer. */
          astNorm( this, buf );
 
 /* Copy the normalised values to the output pointset. */
-         for ( coord = 0; coord < ncoord_out; coord++ ) {
+         for ( coord = 0; coord < naxes; coord++ ) {
             ptr_out[ coord ][ point ] = buf[ coord ];
          }
       }

src/region.c

@@ -267,6 +267,9 @@ f     - AST_SHOWMESH: Display a mesh of points on the surface of a Region
 *        is cleared in the copy. This means that if a component Region within
 *        a CmpRegion is copied, a dump of the resulting copy will include the
 *        FrameSet.
+*     28-OCT-2021 (DSB):
+*        Modified astGetRegionMesh so that meshes for SkyFrame regions that cross
+*        zero longitude do not include jumps of 2.PI in logitude.
 *class--
 
 *  Implementation Notes:
@@ -9317,12 +9320,17 @@ f        The global status.
 *     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).
+*     - If the Region defines an area within a SkyFrame that traverses
+*     zero longitude, the returned positions will be normalised to avoid
+*     jumps of 2.PI radians in longitude (i.e. it will include longitude
+*     values less than zero or greater than 2.PI).
 
 *--
 */
 
 /* Local Variables: */
    AstPointSet *pset;       /* PointSet holding mesh/grid axis values */
+   AstPointSet *temp;       /* PointSet holding normalised mesh/grid axis values */
    double **ptr;            /* Pointer to mesh/grid axes values */
    double *p;               /* Pointer to next input axis value */
    double *q;               /* Pointer to next output axis value */
@@ -9351,12 +9359,18 @@ f        The global status.
          } else {
             pset = astRegBaseGrid( this );
          }
+
       } else {
          if( surface ) {
             pset = astRegMesh( this );
          } else {
             pset = astRegGrid( this );
          }
+
+/* Normalise the points to avoid discontinuities (e.g. at zero longitude). */
+         temp = astNormalPoints( this, pset, 1, NULL );
+         pset = astAnnul( pset );
+         pset = temp;
       }
 
 /* Return the number of points in the mesh or grid. */
@@ -10947,6 +10961,7 @@ f        The global status.
 
 /* Local Variables: */
    AstPointSet *ps;           /* PointSet holding mesh */
+   AstPointSet *temp;         /* PointSet holding normalised mesh */
    char *buffer = NULL;       /* Buffer for line output text */
    char buf[ 40 ];            /* Buffer for floating poitn value */
    double **ptr;              /* Pointers to the mesh data */
@@ -10963,6 +10978,11 @@ f        The global status.
    ps = astRegMesh( this );
    if( ps ) {
 
+/* Normalise it to avoid discontinuities in longitude etc */
+      temp = astNormalPoints( this, ps, 1, NULL );
+      ps = astAnnul( ps );
+      ps = temp;
+
 /* Get the number of axis values per position, and the number of positions. */
       nax = astGetNcoord( ps );
       np = astGetNpoint( ps );

sun_master.tex

@@ -22472,6 +22472,10 @@ \subsection{\xlabel{changes}\xlabel{list_of_most_recent_changes}Changes
 in such a way as to avoid sudden jumps of 360 degrees in longitude within
 groups of points that span the longitude origin.
 
+- The mesh of points returned by astGetRegionMesh and astShowMesh are now
+normalised to avoid discontinuities in celestial longitude. This uses the
+new astNormPoints methid described in the previous item.
+
 \item A bug has been fixed in the KeyMap class that caused astMapGet1<X>
 functions to return a vector length of 1 for KeyMap entries with an
 undefined value. A vector length of zero is now returned in such cases.