[x3d-public] Nurbs control points, preweighted or not ?

[Andreas Plesch]

Thanks, very interesting. The formula png does not show for me directly but
scrolling down in

https://www.web3d.org/documents/specifications/14772-1/V2.1/

to section 4.16.2 shows the equation and the explanation of the variables.

Just to confirm:

V_i,j is  the mesh of control points, likely meaning the value of the
controlPoint field.

Note that in the formula V_i,j is multiplied by their weight w_i,j in the
numerator, which requires that V_i,j are given not premultiplied.

Is it time adopt the same formula for X3D v.4.0 ?

[In theory, it is possible to think about a slower transition path by
introducing new nodes or new fields such as controlPointL (local) for
non-weighted controlPoints but I think a clean break is better.]

-Andreas

On Thu, May 21, 2020 at 10:12 PM J. Scheurich <mufti11 at web.de> wrote:

> BTW: the NURBS formula in VRML97 Amd1. has a extra weight variable:
>
>
> https://www.web3d.org/documents/specifications/14772-1/V2.1/Images/NURBEq.png
>
> w   is the weight
>    i
> V   is the controlpoint
>    i
>
> Maybe the X3D standart should use a similar formula ?
>
> so long
> MUFTI
>


-- 
Andreas Plesch
Waltham, MA 02453
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