[x3d-public] Inconsistencies in Requirement

[Leonard Daly]

Just answering one item at the end (and so deleting all of the 
intervening text...)
>
>
>     >
>     > Overall, it looks like it may be necessary to rely on more than the
>     > DOM alone for DEF/USE functionality.
>
>     Offering another possibility. Unreal (and I think Unity) create a
>     class
>     for each object. If something is "copied", then it is sub-classed from
>     the original class. Changes to the parent propagate to all subclasses;
>     however, a sub-class can override any property (which would then
>     propagate to sub-sub-classes). I think that means in "X3D"-speak, the
>     "DEF" node defines the master class. Any node that "USE"s it would
>     create a subclass. A USE node could also redefine fields for that
>     subclass, and even make itself available for subclassing by using
>     a DEF
>     statement. This would look something like:
>     ...
>

> Svg also allows reusing a modified use for subclassing, judging from 
> the spec. . I have never tried this.
>
> Could be cool. There may be a chance to make this a backwards 
> compatible addition to x3d ?
>
> Trying to come up with a practical use case. Cars. Blue Cars. Blue 
> cars with lights on.

Examples where you might wish to sub-class an object. You have one 
master car wheel. The ones on the other side need to have their geometry 
inverted, but not their rotation characteristics. The ones in front 
turn, the ones in back don't. Going around corners cause the tires to 
rotate at different speeds.

Another one is trees. They may all be the same, but they will bend 
differently depending on how the wind blows through the forest.

The people who build Unreal environments do this all time. I can ask a 
couple of illustrated examples if that would help.


-- 
*Leonard Daly*
3D Systems & Cloud Consultant
LA ACM SIGGRAPH Chair
President, Daly Realism - /Creating the Future/
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