[semantics-public] [x3d-public] representing DEF/USE information

[Brutzman, Donald (Don) (CIV)]

OK I'll bite...

On 11/7/2019 12:24 PM, GPU Group wrote:
> IDEA: a stack-based method for default USE

hmmm

> In the past I've used Switch -1 to hide pre-defined nodes for later USE.

Me too.  Great technique.

For anyone who wants to see an example, please see

	X3D Example Archives: X3D for Web Authors, Chapter 09 Event Utilities Scripting, Integer Sequencer Road Sign Switcher
	https://x3dgraphics.com/examples/X3dForWebAuthors/Chapter09EventUtilitiesScripting/IntegerSequencerRoadSignSwitcherIndex.html

Similar approach could apply a separate TouchSensor and IntegerTrigger, shape by shape, to each select an appropriate child under a single Switch.  Pretty common technique.

> Another idea: to have some generic way to change a default via a stack of some sort:
> <Stack name="material" USE='funnyMaterial'>
> <Shape>
> - no material mentioned, no USE here, gets the default which is funnyMaterial
> </Shape>
> <Stack name='material' USE='seriousMaterial'>
> <Shape>
> - no material mentioned, gets default which is now seriousMaterial
> </Shape>
> </Stack> - pops serious
> <Shape>
> - no material mentioned, gets default which is back to funnyMaterial
> </Shape>
> </Stack> - pops funny
> <Shape>
> - no material mentioned, gets x3d default material
> </Shape>
> But I haven't thought about when / what other scenarios that would be useful for. Just something new related to DEF/USE.
> -Doug Sanden

For this possibility here is a slippery slope to worry about.  It is starting to look like a programming language... Looks like it would either
a. require Script logic, or
b. become unpredictable/nondeterministic.

Both are more complex, and thus hard to encourage.  Also not sure that a Stack adds some new/valuable capability that can't be accomplished already with the existing palette of X3D nodes.

If there is a use case that significantly eases existing modeling, then maybe.  But our current Event Utility nodes are pretty darn simple so they will be tough to surpass.

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