Previously, when marker or hash lines were rendered using interval
or center point place placement, the symbol angles were determined
by taking the exact line orientation at the position of the symbol.
This often leads to undesirable rendering effects, where little
jaggies or corners in lines which occur at the position of the
symbol cause the marker or hash line to be oriented at a very
different angle to what the eye expects to see.
With this new option, the angle is instead calculated by averaging
the line over a specified distance either side of the symbol. E.g.
averaging the line angle over 4mm means we take the points along
the line 2mm from either side of the symbol placement, and use these
instead to calculate the line angle for that symbol. This has the
effect of smoothing (or removing) any tiny local deviations from
the overall line direction, resulting in much nicer visual
orientation of marker or hash lines.
Like all symbol settings, the average angle smoothing distance
can be set using mm/pixels/map units/etc, and supports data-defined
values.
Closed rings also correctly consider wrapping around these average
angles from the start/end vertex.
(Sponsored by an anonymous corporate backer)
of layout items when exporting (i.e. disabling of cached item render)
The old issue of semi-transparent pixels around the edge of the page
had reared again. This is caused by the antialiasing while rendering
the page symbol. In order to avoid this, we cater to the most common
use case of having pages with a solid, borderless fill and slightly
extend the fill symbol polygon outside the page by 2 pixels
(determined by trial-and-error). The less common use case of having
a page symbol containing a border suffers by this border being
clipped by a couple of pixels, but we must address the much more
common use case over this.
