Re: Fw: [x3d-public] Size of live Box

[Alan Hudson <giles@yumetech.com>]

George Anastassakis wrote:
> > AFAIK, there is no way to do this currently specified. See the 
> > February thread "Bounding box of live X3DNode" in the list archives.
>
>
> I believe that thread was about getting a bounding box (or, better put, 
> limits, depending on what model's internally used) for any given 
> geometry node. Instead, I'm talking about the very size of primitive 
> geometry nodes to calculate the bounding boxes myself (in fact, said 
> thread was the reason I started writting my own bounding box calculation 
> code). For such nodes, size is very well defined by a number of fields 
> and cannot change in any way other than modifying the field values 
> themselves (which could still not be allowed even if the fields where 
> readable), neither would it's availability make browser implementors 
> adopt any specific approach as to anything (in contrast to providing 
> live bbCenter and bbSize values). So I don't see the point in hiding 
> their values.

There is no way in X3D to say the difference between hiding a value and 
being able to change a value.  Ie the only way to make that value 
accessible is to change it from initializeOnly to inputOutput.

As an inputOutput field you could then change its value.  A possible 
browser optimization on the primitives is to share one instance per size 
internally.  Ie all the boxes of size 2 2 2 would have one bit of 
geometry.  Since you know the box can't change size you can do that sort 
of optimization.  Every time something is made initializeOnly its 
because a browser implementor had a good case for how they could 
optimize speed or memory consumption based on the restriction.  Over 
time we can reexamine these decisions.  But each one was a premeditated 
action.

Another route you could use would be to drop the values into a metadata 
node.  Ie if you have something generating the X3D, then when it writes 
out the node it could also write out a description for your code to read 
later.

Box {
   metadata MetadataString {
      name "Size"
      value ["3 2 3"]
   }
   size 3 2 3
}

--
Alan Hudson

President Yumetech, Inc.                               www.yumetech.com
President Web3D Consortium                             www.web3d.org
206 340 8900
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