"removing and re-adding nodes to the scenegraph", yeah, sounds like a good 

I just got offered a commercial JavaFX project (which I ended up not doing because of all 
my other work) where the client said that they tried doing it themselves, but had all 
kinds of architectural issues they needed me to solve. Personally I experienced something 
similar Gerrit explains here when trying to write my Agenda control, it appears the first 
time you do JavaFX you'll be doing it wrong. Even though the learning curve is much less 
than Swing's, there still is one. It may be a good idea to get some "best 
practices" going.


On 2013-12-30 12:09, Gerrit Grunwald wrote:
I'm pretty sure that one performance drawback in these gauges is related to 
constantly removing and re-adding nodes to the scenegraph in the layoutChildren 
method. This might be the reason why even static drawing code will be handled 
even if it was not necessary. One reason why in the Enzo controls I add nodes 
only once to the scenegraph and from that point on only modify the nodes.
On the Pi I think one reason for performance problems might be (not sure) that 
paths are rastered by the cpu and because I use a lot of paths and the cpu is 
not that powerful it leads to performance decrease when using lots of nodes 
containing paths but that's more a guess...



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Am 30.12.2013 um 11:01 schrieb Felix Bembrick <felix.bembr...@gmail.com>:

Yes Tom, I also came to the conclusion that most of the nodes in those
(awesome) gauges are largely static and would rarely, if ever, become
"dirty" so the inference that it's excessive work on the scenegraph would
seem unlikely as the cause of the performance degradation.

It does look to me that there is some inherent impact on performance
associated simply with having more nodes.  I hope Richard or someone with
intimate knowledge of the innards of JavaFX rendering could chime in here...

On 30 December 2013 20:50, Tom Eugelink <t...@tbee.org> wrote:

I also watched Gerrits presentation, and he put a lot of emphasis on the
difference between drawing using nodes and drawing using CSS. One of the
examples was one of his famous gauges, where he used a number of gradients
to draw the background. His initial approach was one-node-per-gradient, so
a node for the background, one for the upper shadow, one for the lower,
etc. This resulted in a lot of nodes and he says the Pi has a maximum of
about 120 nodes. Now, these background nodes (and all others that make up
the dial) are static nodes, they do not easily go dirty. So I'm not sure
that that is the problem Gerrit experienced.

That said, the other approach where he tries to do as much in one node as
possible, using CSS, insets and multiple backgrounds/fills seems like a
much clear implementation. So there are other advantages as well. But never
the less it would be interesting to see what the performance issue really
is, given your statement.


On 2013-12-30 1:50, Jasper Potts wrote:

My experience was it is not the number of Nodes. It's the number of Nodes
that are changed/dirty in a single frame. So having a scene with 500 nodes
may take a couple of seconds to render first time but then you can animate
a couple of those nodes at 60fps if you done make too big a area dirty.

Performance issues are one of two things too much SceneGraph work or too
much Graphics card work. You can use pulse logger to determine which issue
you are having.


On Dec 29, 2013, at 3:15 PM, Felix Bembrick <felix.bembr...@gmail.com>

I just watched the excellent presentation by Gerrit Grunwald "Use the
Luke" on Parleys and in it he mentions that one of the key ways to
performance is to limit the number of nodes in the scenegraph.  He also
mentions that on such devices as the Raspberry Pi the maximum number of
nodes viable before performance degrades significantly is very, very
limited.  Further, he then goes on to demonstrate that the equivalent
visual appearance can be achieved by other means such as CSS, Canvas etc.
where the number of nodes is much less.

The implication here is that there is a performance-limiting effect of
Nodes.  If the device's GPU is capable of rendering certain graphics
primitives, effects, transitions etc. and JavaFX is capable of "making
happen" by one way or another, I am curious as to why the simple presence
of Nodes limits performance so significantly.

The obvious conclusion is that Nodes use memory and perhaps the
overhead is the cause but given that we are largely talking about GPU
processing I find it hard to believe that it's as simple as this.

So what is it about the nature of Nodes that causes them to have such a
limiting effect on performance?



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