Ok thanks, will look into that function. Because I wonder if the s/w I am using is actually outputting the vertices of each face in a cyclical fashion or just arbitrarily.
Cheers, Ed On Mon, Oct 29, 2012 at 4:23 PM, Nicolas Ribot <nicolas.ri...@gmail.com>wrote: > Yes, it looks like some points were not put in the right order before > building a polygon, thus these "butterfly" polygons you generated. > If the formed polygon are expected to be convex, you could use > st_convexhull on the point cloud to generate the polygons. > > On 29 October 2012 16:09, Ed Linde <edoli...@gmail.com> wrote: > > Thanks Nicolas! Will look at the script that generated the polygon text.. > > must have goofed something up there. > > > > > > On Mon, Oct 29, 2012 at 4:05 PM, Nicolas Ribot <nicolas.ri...@gmail.com> > > wrote: > >> > >> Hi, > >> > >> No. this is because some of your polygons are not valid: > >> for instance: > >> select st_isvalid('POLYGON ((593921 5219610 803,593921 5219610 > >> 818,593921 5219620 818,593921 5219620 803,593921 5219610 > >> 803))'::geometry); > >> NOTICE: Too few points in geometry component at or near point 593921 > >> 5219610 803 > >> st_isvalid > >> ------------ > >> f > >> (1 row) > >> > >> you can control this with st_isvalid, st_isvalidReason and correct > >> them with st_makeValid. > >> > >> Use only valid objects before processing them with Postgis functions. > >> > >> Nicolas > >> > >> On 29 October 2012 16:03, Ed Linde <edoli...@gmail.com> wrote: > >> > Thanks Nicolas. Just about the error, is this because the line > segments > >> > are > >> > too close > >> > and postgis 2.0 could not handle this? If so is there a workaround, > even > >> > if > >> > it means > >> > slightly having to "perturb" each point's position to not run into > this > >> > bug. > >> > I was really hoping that the intersection of two polygonal shapes in > 3D > >> > would be fairly > >> > simple in postgis 2.0 :( > >> > > >> > Ed > >> > > >> > > >> > On Mon, Oct 29, 2012 at 4:00 PM, Nicolas Ribot < > nicolas.ri...@gmail.com> > >> > wrote: > >> >> > >> >> If the points are computed in the right order, you can store them and > >> >> pass them to st_makeLine and st_makePolygon. > >> >> If not, you can form a segment between 2 closest points and connect > it > >> >> to the closest points. > >> >> > >> >> On 29 October 2012 15:37, Ed Linde <edoli...@gmail.com> wrote: > >> >> > Hi All, > >> >> > Thanks for the tips! Just another thing, when I compute the > >> >> > "transition > >> >> > points" on each edge (shown as red points in my pdf). > >> >> > I need to join them to make a polygon. Wondering how I can connect > >> >> > them > >> >> > together so that I start with a point and end on it > >> >> > to form a closed polygon? > >> >> > > >> >> > Cheers, > >> >> > Ed > >> >> > > >> >> > > >> >> > On Mon, Oct 29, 2012 at 3:03 PM, Stephen Woodbridge > >> >> > <wood...@swoodbridge.com> wrote: > >> >> >> > >> >> >> Hi Ed, > >> >> >> > >> >> >> Well if clarifies one thing at least, you can ignore Mike's > >> >> >> st_Relate > >> >> >> because 5 is not adjacent to a linear edge, it is only adjacent > to a > >> >> >> vertex, > >> >> >> so st_touches should work fine. > >> >> >> > >> >> >> so you are looking for: > >> >> >> > >> >> >> 1. a specific triangle by id > >> >> >> 2. that intersects triangle VC > >> >> >> 3. and the triangles adjacent to triangle by id > >> >> >> 4. and those that are contained in VC > >> >> >> 5. sorted by distance to P1 limit 1 > >> >> >> > >> >> >> so something like: > >> >> >> > >> >> >> select id, the_geom > >> >> >> from (select id, the_geom as adjacent > >> >> >> from triangles > >> >> >> where st_touches(the_geom, > >> >> >> (select the_geom > >> >> >> from triangles a, > >> >> >> (select the_geom as vc > >> >> >> from vc_table > >> >> >> where id='p1') b > >> >> >> where a.id=4)) c > >> >> >> order by st_distance(c.the_geom, (select the_geom > >> >> >> from points > >> >> >> where id='p1')) asc limit 1; > >> >> >> > >> >> >> Untested, but should give you a model to work with. > >> >> >> > >> >> >> -Steve W > >> >> >> > >> >> >> > >> >> >> > >> >> >> On 10/29/2012 6:57 AM, Ed Linde wrote: > >> >> >>> > >> >> >>> Attached is a figure. Where the dotted line is the boundary of > the > >> >> >>> voronoi cell whose > >> >> >>> generator is point P1. So triangle "4" intersects with the > voronoi > >> >> >>> boundary, but we are > >> >> >>> interested in the adjacent triangles of triangle 4, which are > >> >> >>> closer > >> >> >>> to > >> >> >>> point P1. > >> >> >>> For example, triangle 5. > >> >> >>> > >> >> >>> Hope this helps. > >> >> >>> Cheers, > >> >> >>> Ed > >> >> >>> > >> >> >>> On Mon, Oct 29, 2012 at 11:50 AM, Nicolas Ribot > >> >> >>> <nicolas.ri...@gmail.com > >> >> >>> <mailto:nicolas.ri...@gmail.com>> wrote: > >> >> >>> > >> >> >>> Could you draw a figure ? > >> >> >>> > >> >> >>> Nicolas > >> >> >>> > >> >> >>> On 29 October 2012 11:03, Ed Linde <edoli...@gmail.com > >> >> >>> <mailto:edoli...@gmail.com>> wrote: > >> >> >>> > Hi All, > >> >> >>> > Thanks for the suggestions. > >> >> >>> > For 1) I will look into how ST_touches works and see if it > >> >> >>> can > >> >> >>> pick up all > >> >> >>> > the adjacent polygons to > >> >> >>> > the one I have. And also look into Mike's suggestion on > >> >> >>> ST_relate...though I > >> >> >>> > must admit it looks > >> >> >>> > more complex. > >> >> >>> > For 2) I will try to clarify it a bit more... its harder > to > >> >> >>> do > >> >> >>> without a > >> >> >>> > figure :) but here goes. > >> >> >>> > > >> >> >>> > Lets say we have a point Q which is the generator of a > >> >> >>> voronoi > >> >> >>> cell. Now I > >> >> >>> > compute the > >> >> >>> > intersection between the voronoi cell boundaries and my > >> >> >>> triangulation (Set > >> >> >>> > of polygons) > >> >> >>> > using ST_intersect. Once I have these triangles.. I say > pick > >> >> >>> one > >> >> >>> triangle T > >> >> >>> > that is > >> >> >>> > intersecting the voronoi cell boundary of Q. > >> >> >>> > For all the triangles adjacent to T, I need to know which > >> >> >>> triangles are > >> >> >>> > INSIDE the voronoi > >> >> >>> > boundary (closer to Q) and which adjacent triangles are > just > >> >> >>> OUTSIDE the > >> >> >>> > voronoi > >> >> >>> > boundary (farther from Q). I am basically testing for a > >> >> >>> certain > >> >> >>> property by > >> >> >>> > "shrinking" the > >> >> >>> > voronoi cell (closer to Q) and another property when > >> >> >>> "expanding" > >> >> >>> the voronoi > >> >> >>> > cell (away from Q). > >> >> >>> > Just need to make this division of triangles. Haven't > >> >> >>> thought > >> >> >>> of > >> >> >>> a nice way > >> >> >>> > to do this in postgis 2.0 > >> >> >>> > So any suggestions would greatly help. > >> >> >>> > > >> >> >>> > Thanks, > >> >> >>> > Ed > >> >> >>> > > >> >> >>> > On Mon, Oct 29, 2012 at 10:15 AM, Mike Toews > >> >> >>> <mwto...@gmail.com > >> >> >>> <mailto:mwto...@gmail.com>> wrote: > >> >> >>> >> > >> >> >>> >> On 29 October 2012 21:33, Ed Linde <edoli...@gmail.com > >> >> >>> <mailto:edoli...@gmail.com>> wrote: > >> >> >>> >> > Hi All, > >> >> >>> >> > I need help with 2 hard problems. I store triangles in > a > >> >> >>> table > >> >> >>> as > >> >> >>> >> > POLYGON. > >> >> >>> >> > > >> >> >>> >> > 1. I want to know for a given triangle, which triangles > >> >> >>> share > >> >> >>> an edge > >> >> >>> >> > (adjacent) with this triangle. > >> >> >>> >> > >> >> >>> >> Sounds like you have a finite element mesh with nodes and > >> >> >>> elements. > >> >> >>> >> You can use ST_Relate with pattern 'FF2F11212' to pick > out > >> >> >>> elements > >> >> >>> >> that share the same edge. This DE-9-IM is sort-of a > custom > >> >> >>> ST_Touches, > >> >> >>> >> but only takes linear boundary overlaps. So if you have a > >> >> >>> table > >> >> >>> >> "elements", and you want to find ones that touch ID 567: > >> >> >>> >> > >> >> >>> >> SELECT elements.* > >> >> >>> >> FROM elements, elements as e > >> >> >>> >> WHERE e.id <http://e.id> = 567 AND > >> >> >>> > >> >> >>> >> ST_Relate(elements.geom, e.geom, 'FF2F11212'); > >> >> >>> >> > >> >> >>> >> I'm not certain about your second question. > >> >> >>> >> > >> >> >>> >> -Mike > >> >> >>> >> _______________________________________________ > >> >> >>> >> postgis-users mailing list > >> >> >>> >> postgis-users@postgis.refractions.net > >> >> >>> <mailto:postgis-users@postgis.refractions.net> > >> >> >>> > >> >> >>> >> > >> >> >>> http://postgis.refractions.net/mailman/listinfo/postgis-users > >> >> >>> > > >> >> >>> > > >> >> >>> > > >> >> >>> > _______________________________________________ > >> >> >>> > postgis-users mailing list > >> >> >>> > postgis-users@postgis.refractions.net > >> >> >>> <mailto:postgis-users@postgis.refractions.net> > >> >> >>> > >> >> >>> > > >> >> >>> http://postgis.refractions.net/mailman/listinfo/postgis-users > >> >> >>> > > >> >> >>> _______________________________________________ > >> >> >>> postgis-users mailing list > >> >> >>> postgis-users@postgis.refractions.net > >> >> >>> <mailto:postgis-users@postgis.refractions.net> > >> >> >>> > >> >> >>> > http://postgis.refractions.net/mailman/listinfo/postgis-users > >> >> >>> > >> >> >>> > >> >> >>> > >> >> >>> > >> >> >>> _______________________________________________ > >> >> >>> postgis-users mailing list > >> >> >>> postgis-users@postgis.refractions.net > >> >> >>> http://postgis.refractions.net/mailman/listinfo/postgis-users > >> >> >>> > >> >> >> > >> >> >> _______________________________________________ > >> >> >> postgis-users mailing list > >> >> >> postgis-users@postgis.refractions.net > >> >> >> http://postgis.refractions.net/mailman/listinfo/postgis-users > >> >> > > >> >> > > >> >> > > >> >> > _______________________________________________ > >> >> > postgis-users mailing list > >> >> > postgis-users@postgis.refractions.net > >> >> > http://postgis.refractions.net/mailman/listinfo/postgis-users > >> >> > > >> >> _______________________________________________ > >> >> postgis-users mailing list > >> >> postgis-users@postgis.refractions.net > >> >> http://postgis.refractions.net/mailman/listinfo/postgis-users > >> > > >> > > >> > > >> > _______________________________________________ > >> > postgis-users mailing list > >> > postgis-users@postgis.refractions.net > >> > http://postgis.refractions.net/mailman/listinfo/postgis-users > >> > > >> _______________________________________________ > >> postgis-users mailing list > >> postgis-users@postgis.refractions.net > >> http://postgis.refractions.net/mailman/listinfo/postgis-users > > > > > > > > _______________________________________________ > > postgis-users mailing list > > postgis-users@postgis.refractions.net > > http://postgis.refractions.net/mailman/listinfo/postgis-users > > > _______________________________________________ > postgis-users mailing list > postgis-users@postgis.refractions.net > http://postgis.refractions.net/mailman/listinfo/postgis-users >
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