[x3d-public] Typo in spec ?

[Joe D Williams]

< An MFVec4x field or event specifies zero or more 3D homogeneous or 
4D vectors.", with the 'x' replaced by 'f' or 'd' as appropriate.

please don't forget SFRotation

tha main one for MFVec4f i remember is TextureCoordinate4D

Thanks,
Joe





----- Original Message ----- 
From: "Roy Walmsley" <roy.walmsley at ntlworld.com>
To: "'Andreas Plesch'" <andreasplesch at gmail.com>
Cc: "'X3D Graphics public mailing list'" <x3d-public at web3d.org>
Sent: Tuesday, September 29, 2015 5:44 AM
Subject: Re: [x3d-public] Typo in spec ?


> Andreas,
>
> You make a good point below. There is no reason why the SFVec4x 
> fields could not be used as a general 4D vector. The text could be 
> modified to read, for example:
>
> "The SFVec4x field or event specifies a three-dimensional (3D) 
> homogeneous vector or a four-dimensional (4D) vector. An MFVec4x 
> field or event specifies zero or more 3D homogeneous or 4D 
> vectors.", with the 'x' replaced by 'f' or 'd' as appropriate.
>
> Roy
>
> -----Original Message-----
> From: Andreas Plesch [mailto:andreasplesch at gmail.com]
> Sent: 29 September 2015 13:09
> To: Roy Walmsley; Richard F. Puk
> Cc: X3D Graphics public mailing list
> Subject: Re: [x3d-public] Typo in spec ?
>
> Apologies, I had overlooked the significance of the word homogeneous 
> as used in projective geometry. As long as the SFVec4f field is used 
> only in this way, the spec. Is clear (clipplane uses it consistent 
> with that definition). In this case, saying "homogenous coordinate" 
> rather than "vector" could be more specific. But why restrict the 
> definition ? Could it become a general 4d vector ? This way, the 
> fourth coordinate could be used as time or for volumetric 
> attributes.
>
> Andreas
>
> On September 29, 2015, at 5:24 AM, Roy Walmsley 
> <roy.walmsley at ntlworld.com> wrote:
>
> Hi Andreas and Dick,
>
> I can see that it could be confusing referring to an SFVec4d as a 3D 
> homogeneous vector. However, technically, this is the correct 
> description, the term 'homogeneous' implying the extra dimension to 
> the standard three dimensional vector. And the remainder of the 
> paragraph points out that "
> SFVec4d's and MFVec4d's are represented as a 4-tuple of 
> double-precision floating point values ...", thus clarifying the 
> definition. The final paragraph gives the default value with the 
> 4-tuple.
>
> The text quoted above could be expanded to incorporate the 
> components, thus reading, " SFVec4d's and MFVec4d's are represented 
> as a 4-tuple (components x, y, z, w) of double-precision floating 
> point values ...". The danger in doing this is that it might imply a 
> definition of the component names. And it is inconsistent with 
> other definitions. So I am inclined not to support such a change.
>
> Comments are welcomed. I just offered the idea for consensus 
> building.
>
> Regards,
>
> Roy
>
> -----Original Message-----
> From: x3d-public [mailto:x3d-public-bounces at web3d.org] On Behalf Of 
> Richard F. Puk
> Sent: 29 September 2015 05:16
> To: 'Andreas Plesch'; 'X3D Graphics public mailing list'
> Subject: Re: [x3d-public] Typo in spec ?
>
> Hi, Andreas --
>
> A 3D homogeneous vector consists of four components: x, y, z, w.
>
>  -- Dick
>
> /******************************************
> | Richard F. Puk, Ph.D., President
> | Intelligraphics Incorporated
> | 7644 Cortina Court
> | Carlsbad, CA  92009-8206
> | Tel: +1-760-753-9027  Mobile:  +1-760-809-9027
> | Email:  puk at igraphics.com
> \******************************************
>
>
>
>
> -----Original Message-----
> From: x3d-public [mailto:x3d-public-bounces at web3d.org] On Behalf Of 
> Andreas Plesch
> Sent: Monday, September 28, 2015 5:45 PM
> To: X3D Graphics public mailing list
> Subject: [x3d-public] Typo in spec ?
>
> http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/fieldsDef.
> html#SFVec4dAndMFVec4d
> has
> " The SFVec4d field or event specifies a three-dimensional (3D) 
> homogeneous vector."
> as a first sentence.
>
> Should this instead say " The SFVec4d field or event specifies a 
> four-dimensional (4D) homogeneous vector." ?
>
> Andreas
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