[mapserver-dev] Offset x -99 rendering Problem (and possibly a solution)

[Steve Lime]

Will take a peek at this tonite (and the other patch)...

Steve

>>> On 2/20/2009 at 7:44 AM, in message
<d2b988930902200544r57219a84nec0dbf3b27c53ab8 at mail.gmail.com>, thomas bonfort
<thomas.bonfort at gmail.com> wrote:
> Torsten,
> I won't have time to look into this before 5.4 (there's also another
> patch sitting in trac for another issue with offset lines).
> thanks for looking into this, and hoping you can wait until a 5.4.x release 
> .
> 
> (wink: I won't be offended if another dev wants to tackle this  before then 
> )
> regards,
> 
> thomas
> 
> On Mon, Feb 16, 2009 at 09:43, Torsten Weber <TWeber at traffic-consult.de> wrote:
>> Hi all,
>>
>> in our application we need to be able to display line objects which in
>> some case bare the same coordinates used in reverse order.
>> In our case a travel route (line object) on a street map consists of the
>> same street (bearing the same coordinates) used in both directions.
>>
>> We use the offset to mark the affected direction of traffic flow of an 
> event.
>> If the event affects both directions and the directions are not seperated by
>> contruction, a geometry will be generated which has coordinates in reversed
>> order.
>>
>> The offset calculation in maputils.c checks for equal direction only by
>> checking the gradient but not for reversed direction, so a point will be 
> lost
>> and next point is calculated to "nowhere".
>>
>> We've applied a patch to our local mapserver source which solves this for 
> our
>> needs. We changed line 1530 to line 1532 in maputils.c from
>>                              if(k==k0) continue; /* checking equal direction 
> */
>>                                x = (q-q0)/(k0-k);
>>                                y = k*x+q;
>>
>> to
>>                              if (k==k0) {
>>                                if ((dx<0&&dx0>0)||(dx>0&&dx0<0)) { //reversed??
>>                                  ret->line[i].numpoints++;
>>                                  ret->line[i].point=realloc(ret->line[i].point,
>> sizeof(pointObj)*ret->line[i].numpoints);
>>                                  ret->line[i].point[idx].x =
>> p->line[i].point[j-1].x-ox;
>>                                  ret->line[i].point[idx].y = 
> p->line[i].point[j-1].y-oy;
>>                                  idx++;
>>                                  x = p->line[i].point[j-1].x+ox;
>>                                  y = p->line[i].point[j-1].y+oy;
>>                                } else {
>>                                  continue;
>>                                }
>>                              } else {
>>                                x = (q-q0)/(k0-k);
>>                                y = k*x+q;
>>                              }
>>
>> It would be nice, if this can find its way to the next mapserver release.
>>
>> With regards
>>
>> Torsten Weber
>>
>> _______________________________________________
>> mapserver-dev mailing list
>> mapserver-dev at lists.osgeo.org 
>> http://lists.osgeo.org/mailman/listinfo/mapserver-dev 
>>
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