[X3D-Public] [Cad] revising CADInterchange profile

Alan Hudson alan at shapeways.com
Fri Aug 17 10:53:51 PDT 2012

On 8/17/2012 9:52 AM, Don Brutzman wrote:
> Also needed:
> * ViewpointGroup
> ** Allows nesting of Viewpoints within models without exploding or overloading the Viewpoint list, which is an essential tool for user navigation.
> Tesselation consistency
>      Exporters can significantly reduce file size using primitive-geometry nodes (e.g. Cylinder, Disk2D, etc.)
>      Tesselation quality is not strictly defined in X3D
>      In order to match polygonal tessellation strictly and avoid "cracks" between adjacent geometry, some form of association is needed (similar to the NURBSet node)
>      All CAD geometry appears inside a CADPart node, typically one-by-one within child CADFace nodes
>      CADPart is a natural node for this functionality.  Node semantics can be improved to include this constraint.
> These changes have been collected and will be continue to be improved
> on the following wiki page.
> 	X3D v3.4 CAD Improvements
> 	http://www.web3d.org/x3d/wiki/index.php/X3D_v3.4_CAD_Improvements
> I've named this "v3.4" improvements since that was what we seemed to
> think best during the call, as described in the meeting minutes.
> Continued consideration and improvement is welcome.  This is the list
> that we want to send to browser builders so that they can support CAD.
> all the best, Don
In general the first cad interchange profile was designed to be as 
minimal as possible to exchange geometry between systems.  You proposing 
a pretty big increase in the requirements to implement this profile.  As 
I thought about the problem you just wanted geometric interchange.  So 
things like anchor, fill properties, other viewpoint, viewpoint group 
etc were not needed.  I also avoided having IndexedFaceSet because its a 
relatively expensive node to implement in comparison to the native 
IndexedTri* nodes. Same argument for leaving out box, cylinder, 2D 
primitives etc.  The smaller the profile to better chance you have of 
people implementing the profile.  I wouldn't think about how hard it is 
to implement for a current X3D player but consider what a cad package 
would need in order to add this.

I don't have a lot of focus on this area any more but wanted to get 
across some of the design principals we had in mind for this profile.  
If successfull we figured a larger profile with stuff like this might be 
layered on top of this base profile.

Alan Hudson, Director 3D Tools

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