[x3d-public] event tracing

Andreas Plesch andreasplesch at gmail.com
Thu Nov 3 14:18:24 PDT 2016

On Thu, Nov 3, 2016 at 12:45 PM, Don Brutzman <brutzman at nps.edu> wrote:

> Very interesting.  Wondering, do you think this might lead to violations
> of the loop-breaking rule for events?

Not quite sure what you may refer to. The logging is just logging, nothing
else. When I mentioned seemingly variable processing times for the same
event, I was referring to the same event repeated in different cascades
(x3d timestamps).

> Essentially, the rule says that all event values generated during a given
> event cascade (i.e. between frame draws) are checked.  If two events are
> both produced by the same source into the same ROUTE, then duplication
> (likely a loop) has occurred.  Such recurrences are dropped to avoid
> infinite loops.
> I've always assumed that this means the duplicate events have the same
> timestamp, thinking for typical implementations that is probably what
> occurs.
> However, if the check is performed by each individual ROUTE, which can
> tell if a redraw has occurred since last receiving an eventOut value,
> perhaps strict comparison of timestamp values isn't necessary?

not sure.

> Key references:
> ...
> 29.2.7 Asynchronous scripts
> http://www.web3d.org/documents/specifications/19775-1/V3.3/
> Part01/components/scripting.html#Asynchronousscripts
> "Some languages supported by X3D browsers may allow Script nodes to
> spontaneously generate events, allowing users to create Script nodes that
> function like new X3DSensorNode nodes. In these cases, the Script is
> generating the initial events that causes the event cascade, and the
> scripting language and/or the browser shall determine an appropriate
> timestamp for that initial event. Such events are then sorted into the
> event stream and processed like any other event, following all of the same
> rules including those for looping."

This is similar to events caused by external SAI actions which happen when
they happen. The SAI spec. says somewhere that those SAI events need to
trigger a fresh cascade. cobweb_dom and cobweb may currently sort such
events into the event stream of the current cascade (or perhaps next
scheduled cascade) as is being described for asynchronous scripts but I am
not sure.

One could start to think about testing a loop producing (malicious) ROUTE
or script. The loop could be produced just internally and also somehow by
involving the DOM integration (but any DOM action caused by a x3d event of
the current cascade should always affect/trigger a later cascade).  Is
there a loop example somewhere ?


> ===========================================
> On 11/3/2016 6:32 AM, Andreas Plesch wrote:
>> On Mon, Oct 31, 2016 at 6:54 PM, Don Brutzman <brutzman at nps.edu <mailto:
>> brutzman at nps.edu>> wrote:
>>     Tres cool, thank you for this information Andreas.
>>     Trace performance of your teapot widgets is absolutely tremendous,
>> even while printing trace values on the screen (historically a bog on
>> performance).  No discernible change in perceived responsiveness,
>> with/without firebug tracing, even when i interactively try to provoke
>> sluggishness (running good old Windows 7 firefox).
>> I slightly updated the event logging to use performance.now rather than
>> event.timeStamp which is consistent across browsers and to also report the
>> difference between the x3d timestamp and the time of logging which should
>> happen just after dispatching of the DOM event and before drawing to the
>> webgl canvas. The x3d timestamp is created at the beginning of processing
>> of x3d events for each cascade, I believe. This difference varies
>> considerably, about between 2 ms and 20 ms, even for repeats of the same
>> events. Chrome shows a little less difference on average. So I am not sure
>> how accurate these timings are in relation to when things really happen and
>> what external factors influence these.
>> https://andreasplesch.github.io/cobweb_dom/tests/interactive
>> Transformations.xhtml
>> -Andreas
> all the best, Don
> --
> Don Brutzman  Naval Postgraduate School, Code USW/Br
> brutzman at nps.edu
> Watkins 270,  MOVES Institute, Monterey CA 93943-5000 USA
> +1.831.656.2149
> X3D graphics, virtual worlds, navy robotics http://faculty.nps.edu/brutzma
> n

Andreas Plesch
39 Barbara Rd.
Waltham, MA 02453
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