On Fri, 17 Jul 2020 at 19:34, Andreas Neumann <[email protected]> wrote: > > Hi, > > In our efforts to improve cartographic quality, I'd also like to discuss, if > we could somehow improve the quality of the line-pattern fills, and/or the > antialiasing quality of the qt renderer. A very small change in angle can > change the quality of a line-pattern fill in QGIS pretty or very ugly. > > Also: even if all buildings in the following rendering have the same distance > between lines, some look much "denser" than others. Have a look at the > attached file where I labeled some line fills as ugly and pretty. > > Is there something that QGIS could do to improve the "prettyness" of line > pattern fills, or would this have to change in the qt library? > > Thanks if you have any thoughts on this topic,
Sorry for the delayed reply! This is a long-standing issue in QGIS' polygon fill support. See https://github.com/qgis/QGIS/issues/16100 (filed 2013). Basically, the line pattern symbol type uses a trick to speed up the rendering of features by first making a small tiled raster image of the line pattern, and then painting the polygons using this raster brush. It's nice and fast, and works well for canvas/server renders, but is far from ideal for high quality exports. It's also an issue if you try to use data defined settings on the line sub symbol -- because the pattern is generated using the tiled image, you won't see the expected results if you try to make the appearance of individual lines in the pattern vary. For reference, up until 3.14 the point pattern fill had the same limitation. For 3.14 point pattern fills were improved to now export the fill as vector markers (the same raster brush approach is still used for canvas renders, where speed is more important vs quality). What we need to do is implement a similar fix as was done for the point pattern fill, and render each individual line in a line pattern fill as a proper vector line (during layout exports, or when we detect that the line subsymbol has data defined properties set). Hopefully something we can do for 3.16... Nyall > > Andreas > > _______________________________________________ > QGIS-Developer mailing list > [email protected] > List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer _______________________________________________ QGIS-Developer mailing list [email protected] List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer
