There was some discussion on dev-chat about using SVG for rendering
rotation handles and performance and bitmaps came up in discussion.
This should provide a thinking point for talking about canvas performance
at Fridays meeting.
That led me onto some investigation into Inkscapes canvas performance when
rendering bitmaps and vectors and how chrome handles it. This is about the
only benefit of running on an old laptop.
Anyhow, the notes cover the whole file and subfile (z-order sandwich)
caching for all possible dynamic transforms of objects (that is excluding
node, filter, style modification etc...) which should dramatically improve
the performance of inkscape in anything to do with dynamic transformation
where perfect fidelity isn't so critical because it's blurred to the eye.
It's also very practical on the GPU which has enough fast memory and image
filtering technologies to offer good support and high fidelity with no
noticeable artifacts in the rendering.
oliverthered 9:48 PM
I just had a bit of a look at image drawing performance and there is lag
when I'm dragging the image. That means the image position is being updated
with intermediary points when the mouse has long left that point. scrolling
the view point doesn't seem to have these issues, the performance is still
slower than my web browser. That may be because the browser renders to
over-view-size bitmaps, or a composite of bitmaps and caches them, so all
scrolling involves is translating the cached bitmap.
oliverthered 10:00 PM
vector performance doesn't seem too bad, it's still not great though. does
it use intermediary bitmaps with an alpha channel that are cached so that
translating and scaling etc.. operations operate with optimum performance?
in a similar way to how true type font rendering works in most
applications, except with layers.
so say when you select something the objects with z-orders above and below
the selection are cached to bitmaps as layers so they don't have to be
rendered for every update.
obviously you get a sandwich effect if the selected objects aren't in a
oliverthered 11:16 PM
me running out of memory/swapping or whatever causes chrome to show it's
caching system for rendering and it uses square tiles (deciles) when
rendering this svg file. with square tiles it's easy to clip the vectors so
you can minimize redraw because in addition they over size the view.
oliverthered 11:45 PM
looking at inkscape, when the canvas size is larger than the view area
+-42? inkscape resorts to redrawing the portions of the svg file that are
out of view when they come back into view. where as chrome uses deciles so
that at most the content of the squares are redrawn if they move back into
view and are no longer in cache and at least the squares cache the content
once it's been drawn once (in an over sized view that is square by square
proportioned) it's cached and doesn't have to be drawn again for
translation exercises. with decent filtering square caching can also be
used for scale, rotate and skew with the svg file only being needed to be
redrawn when it's enlarged beyond the cache size.
There's a possibility that this may produce some unwelcome artifacts in
studio production though so it may only be workable during dynamic
operations with the svg file having to be redrawn once the dynamic (and so
blurred by the eye) operation is complete to give production quality
oliverthered 11:50 PM
so all dynamic transforms of svg objects can use bitmap caching deciles as
mentioned about along with the sandwich caching I mentioned earlier when a
fraction of the svg file is modified, nodes, transform, properties, filters
etc... This should work very well on the GPU too as it's ideal for this
kind of compositing.
That should cover animated transforms and path movement (esp in CSS) and
with clipping changes to styles and filters and possibly node movement. It
should be possible to parse this information out of the file so caching can
be optimized with advanced knowledge and not have to be done with "on the
fly" optimization for the various fragments which would get messy.
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