[x3d-public] X3D V4 Thoughts; containerField discussion

[Don Brutzman]

On 12/24/2015 1:52 PM, Joe D Williams wrote:
>> There are a few cases where a node is allowed to be a child of more than one field. The containerField in the child node identifies which parent field this node belongs to.
>
> That is, there  are cases where the containng node can only allow certain child nodes. The containerField tells if the child node is ok for the containing node.

Correct.  containerField matches the field name of the parent node.  Of course node type also has to match.

> Why do we even bother to try to identify which containing field is ok for the node with the containerField to be a child of?

To deal with ambiguity.  For example, Collision can contain a Shape as proxy geometry (containerField="proxy") as well as multiple sibling Shape nodes for rendering (containerField="Rendering").

> Was this attribute invented for X3D XML or was there a similar sort of situation(s) in VRML? If there was, then how was this done in VRML.

Field names are used in VRML97 and X3D ClassicVRML encodings.  The containerField approach allows XML to include the same information tersely.

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