# Documentation Source Text

Check-in [bfc897c9c0]

Overview
Comment: In the GeoPoly documentation, mention that geopoly_ccw() can be used to correct vertex order after geopoly_xform(). Tarball | ZIP archive | SQL archive family | ancestors | descendants | both | files | file ages | folders bfc897c9c02eebf5321dc7c222fabb563223be23d454eec627a487af91dbce55 drh 2018-11-24 20:58:44
Context
 2018-11-26 12:01 Merge typo fix from the 3.25 branch. check-in: 121aeee579 user: drh tags: trunk 2018-11-24 20:58 In the GeoPoly documentation, mention that geopoly_ccw() can be used to correct vertex order after geopoly_xform(). check-in: bfc897c9c0 user: drh tags: trunk 20:24 Minor enhancements and updates to various documents. check-in: 9e12c649c9 user: drh tags: trunk
Changes

Changes to pages/geopoly.in.

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To rotate a polygon by R radians around the point 0, 0: geopoly_xform(\$polygon, cos(\$R), sin(\$R), -sin(\$R), cos(\$R), 0, 0) hd_fragment regpoly geopoly_regular

The geopoly_regular(X,Y,R,N) Function

The geopoly_regular(X,Y,R,N) function returns a convex, simple, regular, equilateral, equiangular polygon with N sides, centered at X,Y, and with ``` ``` > > > > > > > ``` ```275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 ``` ```

To rotate a polygon by R radians around the point 0, 0: geopoly_xform(\$polygon, cos(\$R), sin(\$R), -sin(\$R), cos(\$R), 0, 0)

Note that a transformation that flips the polygon might cause the order of vertexes to be reversed. In other words, the transformation might cause the vertexes to circulate in clockwise order instead of counter-clockwise. This can be corrected by sending the result through the [geopoly_ccw()] function after transformation. hd_fragment regpoly geopoly_regular

The geopoly_regular(X,Y,R,N) Function

The geopoly_regular(X,Y,R,N) function returns a convex, simple, regular, equilateral, equiangular polygon with N sides, centered at X,Y, and with ```