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Some nodes are present only in specific VRML/X3D version. This functions decides it.
For example some nodes can only work in VRML < 2.0, some others only in VRML >= 2.0. There are even some pairs of nodes: for example TConeNode_1 works with VRML < 2.0, TConeNode works with VRML >= 2.0.
NodesManager will use this.
Default implementation of this function returns always True . Generally, I don't try to set this too aggresively — in other words, for all cases when it's sensible, I allow nodes to be used in every VRML/X3D version, even when official specification doesn't. This means that when reading VRML 1.0 files actually a large part of VRML 2.0 is allowed too, and also while reading VRML 2.0 many constructs from VRML 1.0 (officially no longer present in VRML 2.0) are allowed too. I'm trying to support what I call a "sum of VRML 1.0 and 2.0".
In practice I only use this function when various VRML/X3D versions specify the same node name but
With different fields.
For example Cone and Cylinder have slightly different fields, due to the fact that VRML 2.0 resigned from using TSFBitMask fields.
With different behavior.
For example definitions of Sphere for VRML 1.0 and 2.0 are practically equal. However, the behavior from where to take texture and material info is different — in VRML 1.0 we take last Texture2, Material etc. nodes, while in VRML 2.0 we look in parent Shape's "appearance" field. So once again two different Sphere classes are needed.
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