[X3D-Public] important questions regarding Units proposal

[Richard Puk]

Hi, Don --

With the exception of "time" (i.e., seconds), I believe that all of the units are listed. Please submit comments if you think that there are others that should be mentioned. I systematic search identified only the base units and the derived units.

  -- Dick

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> -----Original Message-----
> From: Don Brutzman [mailto:brutzman at nps.edu]
> Sent: Sunday, June 19, 2011 2:51 PM
> To: npolys at vt.edu
> Cc: Richard F. Puk; Myeong Won Lee; Leonard Daly; X3D Graphics public mailing
> list
> Subject: Re: important questions regarding Units proposal
> 
> cc: working group
> 
> On 6/19/2011 2:02 PM, npolys at vt.edu wrote:
> > It appears the units proposal is now in 3.3
> 
> Original proposal and slides:
> 
> http://www.web3d.org/membership/login/memberwiki/index.php/X3D_Physica
> l_Units_Proposal
> http://web3d.org/membership/login/groups/Korea%20Web3D%20Forum/1%28
> myeong%29Unit_VR.pdf
> 
> Specification changes are in the Concepts section and also Core Component
> http://www.igraphics.com/Standards/ISO_IEC_19775_1_2_PDAM1_Candidate_
> 2011_05_12/Part01/concepts.html
> http://www.igraphics.com/Standards/ISO_IEC_19775_1_2_PDAM1_Candidate_
> 2011_05_12/Part01/components/core.html
> 
> 4.3.6 Standard units and coordinate systems
> 
> Standard units are modifiable from the following defaults
> 
> 	angle 	radian
> 	force 	newton
> 	length 	metre
> 	mass 	kilogram
> 
> which in turn lead to the following derived units:
> 
> 	acceleration 	length/second2
> 	angular_rate 	angle/second
> 	area 	length2
> 	speed 	length/second
> 	volume 	length3
> 
> ======================
> 7.2.5.5 UNIT statement
> 
> X3D applications may explicitly alter the initial base units within an X3D world by
> inserting UNIT statements defining the characteristics of the new default base
> units. At most one UNIT statement shall be provided for each base unit type.
> Only the UNIT statements in the root file apply to an X3D world. If no UNIT
> statements are provided, the initial base units as specified in 4.3.6 Standard units
> and coordinate system shall apply.
> 
> UNIT statements contained in X3D files referenced by Inline nodes or contained
> in X3D files consisting of EXTERNPROTO bodies shall be used to align effected
> units to the base units of the root file before the referenced X3D file content is
> incorporated in the X3D world.
> 
> UNIT statements may only be contained in X3D worlds created for X3D version
> 3.3 or later (as specified in the Header statement). If a version of 3.2 or earlier is
> specified in conjunction with UNIT statements, the browser shall fail.
> 
> A change in a base unit is specified by UNIT statements at the top of the file
> preceding any element content but in the statement order specified in 7.2.5.1
> Organization. The form of the UNIT statement is:
> 
>     UNIT <category> <name> <conversion_factor>
> 
> where <category> is a string specifying one of the categories in Table 4.2,
> <name> is a string that does not contain whitespace that provides a name for
> the new default base unit, and <conversion_factor> is a positive double
> precision value that converts the new default base unit to the initial base unit
> specified in Table 4.2.
> ======================
> 
> Dick:  shouldn't we be listing other units available in our specification?
> Or at least pointing to the relevant ISO specification for these enumerations?
> i couldn't find either in the proposed change.
> 
> 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, virtual worlds, underwater robots     http://faculty.nps.edu/brutzman