[Korea-chapter] [X3D] Agenda items for the Korea chapter meeting (Wed. 5:10pm PST / Thu 10:10am Korea)

[Alan Hudson]

Myeong Won Lee wrote:
> 3. Physical units specification (Myeong Won Lee, The University of Suwon)
> 
> The unit browser is being modified from the previous Physical node definition to 
> the UNIT statements.  There were contradictions in the email discussion of the 
> X3D WG. We must decide amongst the following when determining which criteria 
> should be applied in the implementation of the length units:
> 
> (1) Length units are defined but do not affect the visual scene at all where 
> there is no scaling. They transfer length units information only. In this case, 
> we cannot compare differences in real length when two X3D objects designed 
> separately are read into a scene using an inline node or by reading two X3D 
> files together in a scene.  There is no difference at all in the scene compared 
> with no unit definition.
>
this makes no sense, whats the purpose of length units then.

> (2) Length units are defined and do not scale objects when reading an X3D file, 
> but relative scales are used when reading two units-specified X3D files together 
> in a scene using inline nodes or by importing another unit X3D file. We must not 
> scale objects when reading an X3D file because we cannot see the scaled objects 
> of very large and small objects such as those of astronomical and microorganism 
> size. It is desirable to use the same units in X3D files when it is necessary to 
> have relative scales.
>     
the easiest implementation of units would be a transform that changes
any non meter speced files into meters with an implicit transform that
the top of the file.

Are you suggesting thats not a legal implementation?  A browser can do
better if it detects that all files are the same units or that all files
are really small(ie then everything might get transformed to millimeters).

But you can't force that type of smart implementation on a browser.
Just converting everything to meters must be legal.

You language about "do no scale units when reading an x3d file" makes no
sense to me.  Its one valid implementation.

-- 
Alan Hudson

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