[x3d-public] FloatSequencer ? step functions and optimization, avoiding node bloat

[Don Brutzman]

On 10/6/2017 12:17 PM, Andreas Plesch wrote:
> Here is the
> 
> http://x3dgraphics.com/examples/X3dForWebAuthors/Chapter09-EventUtilitiesScripting/ScriptComplexStateEventsIndex.html

Thanks for looking at this example again Andreas.

I noticed that the 4-state cycle script was keeping track of state value 
[0,1,2,3] as part of inputOutput field buttonPushCount, and so added some text 
labels under a Switch node to help illustrate it.  Pretty simple addition.

	http://x3dgraphics.com/examples/X3dForWebAuthors/Chapter09EventUtilitiesScripting/ScriptComplexStateEventsIndex.html

	http://x3dgraphics.com/examples/X3dForWebAuthors/Chapter09EventUtilitiesScripting/ScriptComplexStateEventsX_ITE.html

Also have applied background color-coding to the pretty-print html documentation 
to help highlight what the purpose of each node.  Redeploying pretty-print 
updates tonight (with thanks to Sung Min Kwon for helpful discussions on this 
topic).
- (Light blue background: behavior node)
- (Grey background: inserted documentation)
- (Magenta background: X3D Extensibility)

	http://x3dgraphics.com/examples/X3dForWebAuthors/Chapter09EventUtilitiesScripting/ScriptComplexStateEvents.html

> converted using a ScalarSequencer (naming following ScalarInterpolator):
> 
> https://quirky-winter.glitch.me/

Trouble report: the push button requires an irregular number of clicks before 
the light changes. (Windows 10 Firefox)

> And here are the relevant changes to the scene
> 
> https://glitch.com/edit/#!/quirky-winter?path=index.html:75:7
> 
> Replacing the script and its custom field declarations, there is now only one 
> Sequencer node, one ColorInterpolator and one additional route, three lines.
> 
> This pattern would be the main intended usage, eg. using sequencer fraction 
> output to get interpolator typed output for use in the scene (colors, 
> orientations, positions ..).
> 
> How does that look ?
> 
> -Andreas

Well the result is certainly simpler, which is good.  To be fair about such a 
comparison though, it is good to realize that this example is intended to 
illustrate such simple Script design for atypical user interaction.  Whatever works.

This case also illustrates the potential usefulness of prototypes, certainly 
ScalarSequencer can be implemented in that fashion.

For the general case of sequencing Float Vec2f Vec3f Vec4f, we considered adding 
such node(s) to the X3D specification.  However we decided against that because 
the same effect is possible when putting adjacent values together in the 
keyValue array, effectively creating step functions.  We left it up to the X3D 
player to be able to avoid sending unchanging intermediate values during a step, 
avoiding excess events.

Probably further prose about step functions is needed, this relates to recent 
discussion about the piecewise-linear interpolating function f(t).

	19.2.2 Linear interpolation
	http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/interp.html#ScalarInterpolator
and
	19.3.1 X3DInterpolatorNode
	http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/interp.html#X3DInterpolatorNode

Perhaps we should add something to spec like:

	NOTE
	Identical adjacent entries in the keyValue array have the effect of defining 
constant-value step functions.

Added a tooltip to the floating-point interpolators about step functions. 
Further information on that term is available on Wikipedia.

	http://www.web3d.org/x3d/content/X3dTooltips.html#ScalarInterpolator

	https://en.wikipedia.org/wiki/Step_function

Such optimization of unchanging events might be good to consider further. 
Perhaps add prose to 19.2.2 such as

"X3D players are not required to send unchanging intermediate values, providing 
a performance enhancement by avoiding the passing excessive superfluous events 
that have no effect."

Similarly added a tooltip hint about that issue to interpolator node 
value_changed entries.

	http://www.web3d.org/x3d/tooltips/X3dTooltips.html#ColorInterpolator

If we add those clarifications to specification, then perhaps (as originally 
expected) there is no need to add floating-point sequencers to the 
specification.  Given eight floating point interpolator nodes that possess such 
capabilities already in the specification, it is preferable to keep the node 
vocabulary as terse and concise as possible.

The eight nodes in 19.2.2 are
ColorInterpolator
CoordinateInterpolator
CoordinateInterpolator2D
NormalInterpolator
OrientationInterpolator
PositionInterpolator
PositionInterpolator2D
ScalarInterpolator

We need to similarly handle the other X3DInterpolatorNode:

	25.3.7 GeoPositionInterpolator
	http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/geodata.html#GeoPositionInterpolator

Thanks for considering these issues.  Anything that we do to support and enhance 
author animation abilities is worthwhile and certainly holds broad value.

p.s. of related interest: can build sequencers for nodes as well.  Examples:

	http://x3dgraphics.com/examples/X3dForAdvancedModeling/Animation/ViewpointSequencerPrototypeIndex.html

	http://x3dgraphics.com/examples/X3dForAdvancedModeling/Animation/CubeWithLabeledSidesViewpointSequencerIndex.html

	http://www.web3d.org/x3d/content/examples//Basic/Geospatial/CaliforniaCampusesIndex.html


> On Sun, Sep 17, 2017 at 11:25 PM, Andreas Plesch <andreasplesch at gmail.com 
> <mailto:andreasplesch at gmail.com>> wrote:
> 
>     I am thinking about how to convert this example of a 4 state button from
>     scripting to event utilities:
> 
>     http://x3dgraphics.com/examples/X3dForWebAuthors/Chapter09-EventUtilitiesScripting/ScriptComplexStateEventsIndex.html
>     <http://x3dgraphics.com/examples/X3dForWebAuthors/Chapter09-EventUtilitiesScripting/ScriptComplexStateEventsIndex.html>
> 
>     Using a Switch driven by an IntegerSequencer driven by the TouchSensor using
>     the next field would work but requires 4 full Shape nodes.
> 
>     If there were a FloatSequencer, it would be possible to use it to provide
>     fractions to a ColorInterpolator to be fed into the bulb material. This
>     would be closer to the script and overall a more direct, and perhaps elegant
>     solution.
> 
>     In general, with a FloatSequencer it would be possible to use all the
>     Interpolators as typed output, in effect converting from boolean.
> 
>     Since such a FloatSequencer is very straightforward to implement (in x3dom
>     almost identical to IntegerSequencer) I will try this but wonder if such a
>     node had been proposed in the past?
> 
>     I suspect that it would be almost trivial to add such a node to any browser
>     and suggest that it would enhance the utility of the event utilities
>     substantially, pun notwithstanding.
> 
>     Any feedback or comment very welcome,
> 
>     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/brutzman