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It seems like m and z snapping is implemented at the "version 4" (in doc) of the function, when a point is used to define the origin of the grid cell. Bu tin the more common ST_Snaptogrid(geometry, size_of_grid) there is no snapping to m and z.<BR>
<BR>
In lwgeom_functions_analytic.c there is a comment on line 790<BR>
<BR>
/* Do not support gridding Z and M values for now */<BR>
grid.ipz=grid.ipm=grid.zsize=grid.msize=0;<BR>
<BR>
<BR>
The problem now if we want those other version to also snap z and m is that we will have to mess up the order of arguments in some way.<BR>
<BR>
In the documentation<BR>
<A HREF="http://postgis.org/documentation/manual-1.5/ST_SnapToGrid.html">http://postgis.org/documentation/manual-1.5/ST_SnapToGrid.html</A><BR>
<BR>
The version of the ordinary snaptogrid function with all arguments <BR>
have this form:<BR>
<B><TT>ST_SnapToGrid</TT></B><TT>(</TT>geometry <TT>geomA</TT>, float <TT>originX</TT>, float <TT>originY</TT>, float <TT>sizeX</TT>, float <TT>sizeY)</TT>;<BR>
<BR>
so, where to put z and m arguments?<BR>
to not change the old ones we have to put them in the end. But to follow the form from before we out to have the originZ and originM before, sizeX<BR>
<BR>
Any ideas?<BR>
<BR>
/Nicklas<BR>
<BR>
<BR>
<BR>
<BR>
On Mon, 2010-10-18 at 17:39 +0200, strk wrote:
<BLOCKQUOTE TYPE=CITE>
<PRE>
On Mon, Oct 18, 2010 at 03:42:58PM +0200, Nicklas Avén wrote:
> Hallo Sandro
>
> I was about to do the same a few weeks ago when I realized that
> snaptogrid is only workin in 2 dimensions now.
>
> I think we said then we should open up for the third dimension in
> snaptogrid to. As I understand it it is all prepared (you are the author
> aren't you :-) ). I have not looked at it since the discussion on the
> list a few weeks ago, but maybe it is easier and faster for you to open
> up for 3D snapping.
Seems like done already, from postgis.sql.in.c:
-- SnapToGrid(input, point_offsets, xsize, ysize, zsize, msize)
-- Availability: 1.2.2 CREATE OR REPLACE FUNCTION ST_SnapToGrid(geometry, geometry, float8, float8, float8, float8) AS 'MODULE_PATHNAME', 'LWGEOM_snaptogrid_pointoff'
LANGUAGE 'C' IMMUTABLE STRICT;
Does up to 4d..
--strk;
() Free GIS & Flash consultant/developer
/\ <A HREF="http://strk.keybit.net/services.html">http://strk.keybit.net/services.html</A>
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