[postgis-users] Problem with 3D polygon intersection test
Ed Linde
edolinde at gmail.com
Tue Oct 30 03:14:02 PDT 2012
Hi Nicolas,
Not quite sure what to make of the output from ST_DumpPoints, how do I
transform it to just raw x,y,z coordinates?
select st_astext(geomtext) from small_tris where id=0;
st_astext
-------------------------------------------------------
POLYGON Z ((10 10 805,20 10 809,10 20 814,10 10 805))
(1 row)
bounds=# select id, st_dumpPoints( geomtext ) from small_tris where id=0;
id | st_dumppoints
----+----------------------------------------------------------------------
0 | ("{1,1}",0101000080000000000000244000000000000024400000000000288940)
0 | ("{1,2}",0101000080000000000000344000000000000024400000000000488940)
0 | ("{1,3}",0101000080000000000000244000000000000034400000000000708940)
0 | ("{1,4}",0101000080000000000000244000000000000024400000000000288940)
(4 rows)
Thanks,Ed
On Tue, Oct 30, 2012 at 11:05 AM, Ed Linde <edolinde at gmail.com> wrote:
> Ok thanks!
>
>
> On Tue, Oct 30, 2012 at 11:04 AM, Nicolas Ribot <nicolas.ribot at gmail.com>wrote:
>
>> st_dumpRings will return the rings (closed linestrings) composing the
>> polygon (exterior first, then interiors)
>> and st_dumpPoints will return all the points forming the rings, in the
>> right order.
>>
>> Nicolas
>>
>>
>> On 30 October 2012 10:56, Ed Linde <edolinde at gmail.com> wrote:
>>
>>> Ok, for a polygon, is there a good postgis function that can return the
>>> edges to me in the
>>> right sequence? Or at least the points that constitute the polygon in
>>> the right order, so I can
>>> generate the edges in a script?
>>>
>>> Thanks,
>>> Ed
>>>
>>>
>>> On Tue, Oct 30, 2012 at 10:46 AM, Ed Linde <edolinde at gmail.com> wrote:
>>>
>>>> Ah drat! Ok then I have to basically do edge intersection tests by
>>>> myself.
>>>> Ah well. bad news! :(
>>>>
>>>>
>>>> On Tue, Oct 30, 2012 at 10:44 AM, Nicolas Ribot <
>>>> nicolas.ribot at gmail.com> wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>> st_intersection is only suitable for 2D operations. Third dimension is
>>>>> not taken into account.
>>>>>
>>>>> Nicolas
>>>>>
>>>>> On 30 October 2012 09:44, Ed Linde <edolinde at gmail.com> wrote:
>>>>>
>>>>>> Hi All,
>>>>>> Is there a simpler test I can do? I am quite sure that I am probably
>>>>>> not using the right
>>>>>> function in my SQL, or not doing the intersection test correctly. Is
>>>>>> there any simpler
>>>>>> way to test this 3D intersection? Am waiting on the postgis gurus to
>>>>>> come along and
>>>>>> give me some ideas, coz I am at my wits ends on this one! :) The
>>>>>> polygons look good
>>>>>> to me when I visualize them, but don't get how all triangles are
>>>>>> found as intersecting?
>>>>>> Anyway will wait.
>>>>>>
>>>>>> Cheers,
>>>>>> Ed
>>>>>>
>>>>>> On Tue, Oct 30, 2012 at 9:00 AM, Ed Linde <edolinde at gmail.com> wrote:
>>>>>>
>>>>>>> Hi All,
>>>>>>> I am having some troubles getting the *ST_Intersect* function to
>>>>>>> work with 3D polygons.
>>>>>>> I have a table to hold triangles as polygons in *"small_tris"*
>>>>>>> Another table for holding the polygonal faces of a 3D voronoi
>>>>>>> diagram in *"vfaces"*
>>>>>>> So now I am trying to do an intersection between the triangles and
>>>>>>> the voronoi faces
>>>>>>> to get the triangles that intersect with the faces. And it seems
>>>>>>> that *ALL* triangles
>>>>>>> are intersecting. I have attached a PDF where I have plotted the
>>>>>>> triangles and the
>>>>>>> voronoi cells. so the box around in red and blue with a major face
>>>>>>> going through is
>>>>>>> the voronoi diagram. The Voronoi partition in 3D is shown at the
>>>>>>> bottom too for clarity
>>>>>>> Can someone please help and let me know what am I doing wrong here?
>>>>>>> Is the select assuming something? So the polygons are flat and the
>>>>>>> intersections
>>>>>>> should just be lines or points. I am under some pressure to get this
>>>>>>> to work, so if
>>>>>>> anyone needs more information to help, the please let me know! :)
>>>>>>>
>>>>>>> Cheers,
>>>>>>> Ed
>>>>>>>
>>>>>>> *-- TABLE SCHEMAS*
>>>>>>> bounds=# \d vfaces;
>>>>>>> Table "public.vfaces"
>>>>>>> Column | Type | Modifiers
>>>>>>> ----------+----------+-----------
>>>>>>> gen_id | integer |
>>>>>>> geomtext | geometry |
>>>>>>>
>>>>>>> bounds=# \d small_tris;
>>>>>>> Table "public.small_tris"
>>>>>>> Column | Type | Modifiers
>>>>>>> ----------+----------+-----------
>>>>>>> id | integer | not null
>>>>>>> v0 | integer |
>>>>>>> v1 | integer |
>>>>>>> v2 | integer |
>>>>>>> geomtext | geometry |
>>>>>>> Indexes:
>>>>>>> "small_tris_pkey" PRIMARY KEY, btree (id)
>>>>>>> "small_idx" gist (geomtext)
>>>>>>>
>>>>>>>
>>>>>>> *
>>>>>>> -- TABLE CONTENT*
>>>>>>> bounds=# select id, st_astext( geomtext ) from small_tris;
>>>>>>> id | st_astext
>>>>>>> ----+-------------------------------------------------------
>>>>>>> 0 | POLYGON Z ((10 10 805,20 10 809,10 20 814,10 10 805))
>>>>>>> 1 | POLYGON Z ((10 20 814,20 10 809,20 20 819,10 20 814))
>>>>>>> 2 | POLYGON Z ((20 20 819,30 10 809,30 20 812,20 20 819))
>>>>>>> 3 | POLYGON Z ((30 10 809,20 20 819,20 10 809,30 10 809))
>>>>>>> 4 | POLYGON Z ((30 20 812,30 10 809,40 10 826,30 20 812))
>>>>>>> 5 | POLYGON Z ((20 20 819,30 20 812,20 30 827,20 20 819))
>>>>>>> 6 | POLYGON Z ((10 20 814,20 20 819,20 30 827,10 20 814))
>>>>>>> 7 | POLYGON Z ((10 40 805,10 30 814,20 30 827,10 40 805))
>>>>>>> 8 | POLYGON Z ((10 50 804,10 40 805,20 40 807,10 50 804))
>>>>>>> 9 | POLYGON Z ((20 30 827,20 40 807,10 40 805,20 30 827))
>>>>>>> 10 | POLYGON Z ((30 30 817,20 40 807,20 30 827,30 30 817))
>>>>>>> 11 | POLYGON Z ((30 40 816,20 50 809,20 40 807,30 40 816))
>>>>>>> 12 | POLYGON Z ((20 40 807,20 50 809,10 50 804,20 40 807))
>>>>>>> 13 | POLYGON Z ((10 30 814,10 20 814,20 30 827,10 30 814))
>>>>>>> 14 | POLYGON Z ((30 30 817,20 30 827,30 20 812,30 30 817))
>>>>>>> 15 | POLYGON Z ((30 20 812,40 20 823,30 30 817,30 20 812))
>>>>>>> 16 | POLYGON Z ((40 20 823,30 20 812,40 10 826,40 20 823))
>>>>>>> 17 | POLYGON Z ((40 20 823,40 10 826,50 10 803,40 20 823))
>>>>>>> 18 | POLYGON Z ((30 30 817,40 20 823,40 30 814,30 30 817))
>>>>>>> 19 | POLYGON Z ((40 20 823,50 20 808,40 30 814,40 20 823))
>>>>>>> 20 | POLYGON Z ((50 20 808,40 20 823,50 10 803,50 20 808))
>>>>>>> 21 | POLYGON Z ((40 30 814,50 20 808,50 30 816,40 30 814))
>>>>>>> 22 | POLYGON Z ((30 30 817,40 30 814,40 40 800,30 30 817))
>>>>>>> 23 | POLYGON Z ((30 40 816,40 40 800,30 50 813,30 40 816))
>>>>>>> 24 | POLYGON Z ((30 40 816,30 30 817,40 40 800,30 40 816))
>>>>>>> 25 | POLYGON Z ((30 50 813,40 40 800,40 50 817,30 50 813))
>>>>>>> 26 | POLYGON Z ((30 40 816,30 50 813,20 50 809,30 40 816))
>>>>>>> 27 | POLYGON Z ((50 40 821,40 50 817,40 40 800,50 40 821))
>>>>>>> 28 | POLYGON Z ((50 50 809,40 50 817,50 40 821,50 50 809))
>>>>>>> 29 | POLYGON Z ((50 40 821,40 40 800,50 30 816,50 40 821))
>>>>>>> 30 | POLYGON Z ((40 30 814,50 30 816,40 40 800,40 30 814))
>>>>>>> 31 | POLYGON Z ((30 30 817,30 40 816,20 40 807,30 30 817))
>>>>>>> (32 rows)
>>>>>>>
>>>>>>> select st_astext(geomtext) from vfaces;
>>>>>>>
>>>>>>> st_astext
>>>>>>>
>>>>>>> -----------------------------------------------------------------------------------------------
>>>>>>> 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))
>>>>>>> POLYGON Z ((51 17.8 799,9 38.8 799,9 51 799,51 51 799,51 17.8 799))
>>>>>>> POLYGON Z ((51 35.2 828,19.4 51 828,51 51 828,51 35.2 828))
>>>>>>> POLYGON Z ((9 9 799,9 38.8 799,51 17.8 799,51 9 799,9 9 799))
>>>>>>> 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))
>>>>>>> POLYGON Z ((9 9 828,9 51 828,19.4 51 828,51 35.2 828,51 9 828,9 9
>>>>>>> 828))
>>>>>>> (6 rows)
>>>>>>>
>>>>>>> *select distinct a.id
>>>>>>> from small_tris a, vfaces b
>>>>>>> where st_intersects (a.geomtext, b.geomtext)
>>>>>>> order by a.id;*
>>>>>>> id
>>>>>>> ----
>>>>>>> 0
>>>>>>> 1
>>>>>>> 2
>>>>>>> 3
>>>>>>> 4
>>>>>>> 5
>>>>>>> 6
>>>>>>> 7
>>>>>>> 8
>>>>>>> 9
>>>>>>> 10
>>>>>>> 11
>>>>>>> 12
>>>>>>> 13
>>>>>>> 14
>>>>>>> 15
>>>>>>> 16
>>>>>>> 17
>>>>>>> 18
>>>>>>> 19
>>>>>>> 20
>>>>>>> 21
>>>>>>> 22
>>>>>>> 23
>>>>>>> 24
>>>>>>> 25
>>>>>>> 26
>>>>>>> 27
>>>>>>> 28
>>>>>>> 29
>>>>>>> 30
>>>>>>> 31
>>>>>>> (32 rows)
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
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>>>>>>
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