[postgis-users] ST_3dintersects returns false for linestrings pairs with touching vertex

[Nicklas Avén]

Hi Alexandre


This seems to be a bug caused by some floating point error or some mis 
handling of the coordinates.


In 3D the intersects function just wrapps ST_3DDistance and checks if it 
returns 0.

So when trying with the same geometries with ST_3DDistance instead it 
returns 3.638977870632214e-12


I will take a look at it.


Could you please file a ticket?


ATB


Nicklas Avén



On 11/12/20 2:46 AM, Alexandre Neto wrote:
> Hi,
>
> I am having a strange issue with st_3dintersects. I have two 
> linestring that share the same end vertex. Nevertheless, using 
> ST_3dintersects returns false.
>
>       SELECT ST_3dintersects(st_geometryfromtext('LINESTRING Z 
> (-27922.1593 -110233.7616 147.2259,-27928.084 -110230.8462 
> 147.3629,-27930.6374 -110229.9248 147.3629,-27931.6207 -110229.587 
> 147.3094,-27932.3841 -110229.275 147.3676,-27933.1861 -110228.9467 
> 147.4365,-27937.0309 -110227.3638 147.7729,-27937.7892 -110227.0474 
> 147.8412,-27938.6259 -110226.6885 147.9075,-27939.4617 -110226.3287 
> 147.9663,-27943.6905 -110224.5169 148.2353,-27944.5442 -110224.1538 
> 148.2687,-27945.6634 -110223.6871 148.2849,-27946.7835 -110223.2224 
> 148.2982,-27952.3498 -110220.9011 148.3594,-27953.4568 -110220.4353 
> 148.3756,-27966.8502 -110214.6482 148.7361,-27969.516 -110213.4996 
> 148.7961,-27972.1805 -110212.3494 148.8566,-27974.1264 -110211.5032 
> 148.9768,-27975.4229 -110210.9441 149.0093)'),
>       st_geometryfromtext('LINESTRING Z (-28001.1829 -110201.8973 
> 149.4396,-28000.3665 -110199.7073 149.3765,-27995.4183 -110201.8041 
> 149.3354,-27975.4229 -110210.9441 149.0093)'))
>
> Any idea what could be happening in here?
>
> Thanks,
>
> Alexandre Neto
>
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