st_dumpRings will return the rings (closed linestrings) composing the polygon (exterior first, then interiors)<div>and st_dumpPoints will return all the points forming the rings, in the right order.</div><div><br></div><div>
Nicolas<br><br><div class="gmail_quote">On 30 October 2012 10:56, Ed Linde <span dir="ltr"><<a href="mailto:edolinde@gmail.com" target="_blank">edolinde@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Ok, for a polygon, is there a good postgis function that can return the edges to me in the <br>right sequence? Or at least the points that constitute the polygon in the right order, so I can<br>generate the edges in a script?<br>
<br>Thanks,<br>Ed<div class="HOEnZb"><div class="h5"><br><br><div class="gmail_quote">On Tue, Oct 30, 2012 at 10:46 AM, Ed Linde <span dir="ltr"><<a href="mailto:edolinde@gmail.com" target="_blank">edolinde@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Ah drat! Ok then I have to basically do edge intersection tests by myself. <div>Ah well. bad news! :(<div><div><br><br><div class="gmail_quote">On Tue, Oct 30, 2012 at 10:44 AM, Nicolas Ribot <span dir="ltr"><<a href="mailto:nicolas.ribot@gmail.com" target="_blank">nicolas.ribot@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi,<div><br></div><div>st_intersection is only suitable for 2D operations. Third dimension is not taken into account.</div>
<div><br></div><div>Nicolas </div><div><br><div class="gmail_quote"><div><div>On 30 October 2012 09:44, Ed Linde <span dir="ltr"><<a href="mailto:edolinde@gmail.com" target="_blank">edolinde@gmail.com</a>></span> wrote:<br>
</div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div>Hi All,<br>Is there a simpler test I can do? I am quite sure that I am probably not using the right <br>
function in my SQL, or not doing the intersection test correctly. Is there any simpler <br>
way to test this 3D intersection? Am waiting on the postgis gurus to come along and<br>
give me some ideas, coz I am at my wits ends on this one! :) The polygons look good<br>to me when I visualize them, but don't get how all triangles are found as intersecting?<br>Anyway will wait.<br><br>Cheers,<br>Ed<br>
<br><div class="gmail_quote">On Tue, Oct 30, 2012 at 9:00 AM, Ed Linde <span dir="ltr"><<a href="mailto:edolinde@gmail.com" target="_blank">edolinde@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi All,<br>I am having some troubles getting the <b>ST_Intersect</b> function to work with 3D polygons. <br>I have a table to hold triangles as polygons in <b>"small_tris"</b><br>Another table for holding the polygonal faces of a 3D voronoi diagram in <b>"vfaces"</b><br>
So now I am trying to do an intersection between the triangles and the voronoi faces<br>to get the triangles that intersect with the faces. And it seems that *ALL* triangles <br>are intersecting. I have attached a PDF where I have plotted the triangles and the <br>
voronoi cells. so the box around in red and blue with a major face going through is <br>the voronoi diagram. The Voronoi partition in 3D is shown at the bottom too for clarity<br>Can someone please help and let me know what am I doing wrong here?<br>
Is the select assuming something? So the polygons are flat and the intersections <br>should just be lines or points. I am under some pressure to get this to work, so if<br>anyone needs more information to help, the please let me know! :) <br>
<br>Cheers,<br>Ed<br><br><b>-- TABLE SCHEMAS</b><br>bounds=# \d vfaces;<br> Table "public.vfaces"<br> Column | Type | Modifiers <br>----------+----------+-----------<br> gen_id | integer | <br> geomtext | geometry | <br>
<br>bounds=# \d small_tris;<br> Table "public.small_tris"<br> Column | Type | Modifiers <br>----------+----------+-----------<br> id | integer | not null<br> v0 | integer | <br> v1 | integer | <br>
v2 | integer | <br> geomtext | geometry | <br>Indexes:<br> "small_tris_pkey" PRIMARY KEY, btree (id)<br> "small_idx" gist (geomtext)<br><br><br><b><br>
-- TABLE CONTENT</b><br>bounds=# select id, st_astext( geomtext ) from small_tris;<br> id | st_astext <br>----+-------------------------------------------------------<br> 0 | POLYGON Z ((10 10 805,20 10 809,10 20 814,10 10 805))<br>
1 | POLYGON Z ((10 20 814,20 10 809,20 20 819,10 20 814))<br> 2 | POLYGON Z ((20 20 819,30 10 809,30 20 812,20 20 819))<br> 3 | POLYGON Z ((30 10 809,20 20 819,20 10 809,30 10 809))<br> 4 | POLYGON Z ((30 20 812,30 10 809,40 10 826,30 20 812))<br>
5 | POLYGON Z ((20 20 819,30 20 812,20 30 827,20 20 819))<br> 6 | POLYGON Z ((10 20 814,20 20 819,20 30 827,10 20 814))<br> 7 | POLYGON Z ((10 40 805,10 30 814,20 30 827,10 40 805))<br> 8 | POLYGON Z ((10 50 804,10 40 805,20 40 807,10 50 804))<br>
9 | POLYGON Z ((20 30 827,20 40 807,10 40 805,20 30 827))<br> 10 | POLYGON Z ((30 30 817,20 40 807,20 30 827,30 30 817))<br> 11 | POLYGON Z ((30 40 816,20 50 809,20 40 807,30 40 816))<br> 12 | POLYGON Z ((20 40 807,20 50 809,10 50 804,20 40 807))<br>
13 | POLYGON Z ((10 30 814,10 20 814,20 30 827,10 30 814))<br> 14 | POLYGON Z ((30 30 817,20 30 827,30 20 812,30 30 817))<br> 15 | POLYGON Z ((30 20 812,40 20 823,30 30 817,30 20 812))<br> 16 | POLYGON Z ((40 20 823,30 20 812,40 10 826,40 20 823))<br>
17 | POLYGON Z ((40 20 823,40 10 826,50 10 803,40 20 823))<br> 18 | POLYGON Z ((30 30 817,40 20 823,40 30 814,30 30 817))<br> 19 | POLYGON Z ((40 20 823,50 20 808,40 30 814,40 20 823))<br> 20 | POLYGON Z ((50 20 808,40 20 823,50 10 803,50 20 808))<br>
21 | POLYGON Z ((40 30 814,50 20 808,50 30 816,40 30 814))<br> 22 | POLYGON Z ((30 30 817,40 30 814,40 40 800,30 30 817))<br> 23 | POLYGON Z ((30 40 816,40 40 800,30 50 813,30 40 816))<br> 24 | POLYGON Z ((30 40 816,30 30 817,40 40 800,30 40 816))<br>
25 | POLYGON Z ((30 50 813,40 40 800,40 50 817,30 50 813))<br> 26 | POLYGON Z ((30 40 816,30 50 813,20 50 809,30 40 816))<br> 27 | POLYGON Z ((50 40 821,40 50 817,40 40 800,50 40 821))<br> 28 | POLYGON Z ((50 50 809,40 50 817,50 40 821,50 50 809))<br>
29 | POLYGON Z ((50 40 821,40 40 800,50 30 816,50 40 821))<br> 30 | POLYGON Z ((40 30 814,50 30 816,40 40 800,40 30 814))<br> 31 | POLYGON Z ((30 30 817,30 40 816,20 40 807,30 30 817))<br>(32 rows)<br><br> select st_astext(geomtext) from vfaces;<br>
st_astext <br>-----------------------------------------------------------------------------------------------<br> POLYGON Z ((51 17.8 799,9 38.8 799,9 51 819.33333333333,19.4 51 828,51 35.2 828,51 17.8 799))<br>
POLYGON Z ((51 17.8 799,9 38.8 799,9 51 799,51 51 799,51 17.8 799))<br> POLYGON Z ((51 35.2 828,19.4 51 828,51 51 828,51 35.2 828))<br> POLYGON Z ((9 9 799,9 38.8 799,51 17.8 799,51 9 799,9 9 799))<br> POLYGON Z ((51 17.8 799,9 38.8 799,9 51 819.33333333333,19.4 51 828,51 35.2 828,51 17.8 799))<br>
POLYGON Z ((9 9 828,9 51 828,19.4 51 828,51 35.2 828,51 9 828,9 9 828))<br>(6 rows)<br><br><b style="color:rgb(51,102,255)">select distinct <a href="http://a.id" target="_blank">a.id</a><br>from small_tris a, vfaces b<br>
where st_intersects (a.geomtext, b.geomtext)<br>
order by <a href="http://a.id" target="_blank">a.id</a>;</b><br> id <br>----<br> 0<br> 1<br> 2<br> 3<br> 4<br> 5<br> 6<br> 7<br> 8<br> 9<br> 10<br> 11<br> 12<br> 13<br> 14<br> 15<br> 16<br> 17<br> 18<br> 19<br>
20<br> 21<br> 22<br>
23<br> 24<br> 25<br> 26<br> 27<br> 28<br> 29<br> 30<br> 31<br>(32 rows)<br><br><img alt=""><br>
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