On Mon, Apr 6, 2015 at 11:59 PM, Jim Graham <james.gra...@oracle.com> wrote:
> We use this one for fast rectangular clipping: >> https://github.com/geotools/geotools/blob/master/modules/ >> library/main/src/main/java/org/geotools/geometry/jts/GeometryClipper.java >> >> It was introduced exactly because java2d does not do that, and can lead >> to OOM easily with large >> shapes united with a dasharray stroke. >> > > If I understand the above correctly you will simplify a polygon to just > the pieces that fall within the clip before you send them to the > rendering/stroking engine? You mention dashing as the main case that you > are concerned with, but doesn't that surgery on the polygon change the dash > pattern? I suppose if you are just viewing the dash pattern as a periodic > decoration then that wouldn't matter, but technically there is only one > correct way for the in-clip dashes to appear. > Yes, you are right it can create visual artifacts. But the speed (important) and stability (very important) benefits are so big that we have no choice. Also, it seems that users are not complaining, and pretty much every open source mapping software I've looked into has implemented something similar. Performance wise the thing is, we sometimes are visualizing only a tiny part of a large geometry in a map, so quickly throwing away the parts that we are not concerned with results in a sizeable benefit (we normally clip at a certain distance from the visible area to avoid part of the artifacts). > > This does point out that our dashing engines (and stroking engines) do not > take the clip into account at all and so generate widened and dashed > geometry for parts of the shape that do not intersect the clip. We should > look at adding that. The more responsible way to add it for dashing would > be to compute the length of any omitted segment and consume the dash phase > as appropriate, but that is much cheaper than generating all of the > segments and then having them widened just to be ignored by the rendering > phase. > Right Cheers Andrea -- == GeoServer Professional Services from the experts! Visit http://goo.gl/NWWaa2 for more information. == Ing. Andrea Aime @geowolf Technical Lead GeoSolutions S.A.S. Via Poggio alle Viti 1187 55054 Massarosa (LU) Italy phone: +39 0584 962313 fax: +39 0584 1660272 mob: +39 339 8844549 http://www.geo-solutions.it http://twitter.com/geosolutions_it *AVVERTENZE AI SENSI DEL D.Lgs. 196/2003* Le informazioni contenute in questo messaggio di posta elettronica e/o nel/i file/s allegato/i sono da considerarsi strettamente riservate. Il loro utilizzo è consentito esclusivamente al destinatario del messaggio, per le finalità indicate nel messaggio stesso. Qualora riceviate questo messaggio senza esserne il destinatario, Vi preghiamo cortesemente di darcene notizia via e-mail e di procedere alla distruzione del messaggio stesso, cancellandolo dal Vostro sistema. Conservare il messaggio stesso, divulgarlo anche in parte, distribuirlo ad altri soggetti, copiarlo, od utilizzarlo per finalità diverse, costituisce comportamento contrario ai principi dettati dal D.Lgs. 196/2003. The information in this message and/or attachments, is intended solely for the attention and use of the named addressee(s) and may be confidential or proprietary in nature or covered by the provisions of privacy act (Legislative Decree June, 30 2003, no.196 - Italy's New Data Protection Code).Any use not in accord with its purpose, any disclosure, reproduction, copying, distribution, or either dissemination, either whole or partial, is strictly forbidden except previous formal approval of the named addressee(s). If you are not the intended recipient, please contact immediately the sender by telephone, fax or e-mail and delete the information in this message that has been received in error. The sender does not give any warranty or accept liability as the content, accuracy or completeness of sent messages and accepts no responsibility for changes made after they were sent or for other risks which arise as a result of e-mail transmission, viruses, etc. -------------------------------------------------------
