[GraphHopper] How graphhopper handle the barrier=gate?

[Peter]

Hi ZhiQiang,

> Actually, you can use turn restriction to avoid the virtual edge.

Yes, but you can disable turn restriction and still want barrier
support. Also currently CH is not working with turn restriction.


> I assume the turn restriction feature was implemented later than
barrier=gate.

Yes, but I think it should not be implemented as a turn restriction
because the access does not really depend on the source edge - if it
does, then it is incorrectly mapped. See here the discussion and open
issue #388:
https://github.com/graphhopper/graphhopper/issues/388#issuecomment-88066385
Additionally if edge a to edge b is not accessible then the opposite is
always false too, which is different to turn restrictions or costs.

BTW: the edge at a gate is not called virtual edge as we 'reserved' this
name for edges creates in the query graph :)

Kind Regards,
Peter

On 22.07.2015 02:41, John Zhao wrote:
> Hi Peter,
>
> I am a little understand why Graphhopper use a virtual edge at gate.
> Cause you may need support car and foot at the same time.
> Then you can disable that virtual edge on car, but enable it on foot.
> That's why you don't just simply break the segment there.
>
> Actually, you can use turn restriction to avoid the virtual edge.
> I assume the turn restriction feature was implemented later than
> barrier=gate.
>
>
> *Best Regards,*
> *ZhiQiang ZHAO*
>
> On Thu, Jul 9, 2015 at 12:23 AM, Peter <graphhopper at gmx.de
> <mailto:graphhopper at gmx.de>> wrote:
>
>     You can block the edge like you restrict access of any other edge:
>     set the access bits to false - it should be something like this:
>     edge.setFlags(encoder.setAccess(edge.getFlags(), false, false))
>
>     Peter
>
>
>     On 09.07.2015 09:13, John Zhao wrote:
>>     Hi Peter,
>>
>>     I understand it's in each flager.
>>     My question is how GH block that zero length edge.
>>     I don't find the corresponding log.
>>
>>     I think there are several ways to handle this:
>>     1. convert it to turn restriction.
>>     2. create a virtual node, but don't connect the virtual node and
>>     real node. Then they are not connected.
>>
>>     But graphhopper use another way:
>>     create a virtual node. then create an virtual edge between the
>>     virtual node and real node.
>>     I guess GH need to make some special configure on the virtual edge.
>>
>>     *Best Regards,*
>>     *ZhiQiang ZHAO*
>>
>>     On Thu, Jul 9, 2015 at 12:08 AM, Peter <graphhopper at gmx.de
>>     <mailto:graphhopper at gmx.de>> wrote:
>>
>>         If and how a barrier is blocking is handled in the specific
>>         FlagEncoder:
>>
>>         https://github.com/graphhopper/graphhopper/blob/master/core/src/main/java/com/graphhopper/routing/util/CarFlagEncoder.java#L86
>>
>>         Regards,
>>         Peter
>>
>>
>>         On 09.07.2015 02:43, John Zhao wrote:
>>>         Hi,
>>>
>>>         I looked into OSMReader.processWay( )
>>>         There is already a lot of comments. But it's still not clear
>>>         to me. :p
>>>
>>>         I understand GH will create a "virtual" node, with the same
>>>         lat/lon.
>>>         And then create a new edge between the 2 nodes.
>>>         But how to block this edge?
>>>         set the direction bit of the zero length edge both to false?
>>>         where is the code?
>>>         // create zero length edge for barrier
>>>         createdEdges.addAll(addBarrierEdge(newNodeId, nodeId, wayFlags, nodeFlags, wayOsmId));
>>>         *Best Regards,*
>>>         *ZhiQiang ZHAO*
>>>
>
>

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