[x3d-public] IndexedTriangleSet defaults

[John Carlson]

I found X3DOM’s Sphere very useful for creating texture and geometry coordinates.   X3D needs an upgrade!

John
> On May 1, 2016, at 10:28 PM, Joe D Williams <joedwil at earthlink.net> wrote:
> 
> I think it was a simple convenience for the author of an indexedfaceset to automatically produce a default texcoord array, mainly by a simple copy of the x and y coords (by not z) of the shape. This should work in all cases even if the ifs is skin of hanim. I think historically, it should be ok if no automated texcoord generation is offered for other shapes than ifs.
> Thanks,
> Joe
> .
> ----- Original Message ----- From: "Andreas Plesch" <andreasplesch at gmail.com>
> To: "Roy Walmsley" <roy.walmsley at ntlworld.com>
> Cc: "X3D Graphics public mailing list" <x3d-public at web3d.org>
> Sent: Monday, April 11, 2016 10:03 AM
> Subject: Re: [x3d-public] IndexedTriangleSet defaults
> 
> 
> Apologies, I took a short cut in the hope to get to the question directly
> but ended up with producing a surprise.
> 
> Not sure how useful the default implementation behaviour for texture
> coordinates of IndexedFaceSets is. Although I can see that there are use
> cases with overall planar geometries and exactly matching map textures.
> 
> Could this implementation behaviour be a candidate for deprecation ? In
> contrast, default texture coordinates for the various convenience
> geometries (box, plane, sphere, elevationgrid ..) are very useful.
> 
> I was coming across this when I looked at three.js and its constructors for
> geometry on which in turn aframe's geometric primitives are based. Three.js
> does not have IndexedFaceSet but it has IndexedTriangleSet without default
> texture coordinates (UV).
> 
> It might be good to harmonize where possible.
> 
> Since aframe is designed to be very extensible and has concepts similar to
> x3d, it may be actually possible to implement a (limited) x3d browser using
> aframe as the underlying framework, with x3d nodes and fields corresponding
> to aframe components. A thought for another time.
> 
> Andreas
> 
> 
> 
> 
> 
> 
> 
> 
> On Mon, Apr 11, 2016 at 10:21 AM, Roy Walmsley <roy.walmsley at ntlworld.com>
> wrote:
> 
>> Hi Andreas,
>> 
>> 
>> 
>> Initially I was surprised by your comment below. As you say, the default
>> value of the *texCoord* field is NULL for the IndexedTriangleSet node.
>> But when I looked at the IndexedFaceSet node, I found that it too has a
>> default value of NULL for the *texCoord* field (see
>> http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/geometry3D.html#IndexedFaceSet).
>> So both are in agreement there.
>> 
>> 
>> 
>> However, I assume you are referring to the text in the penultimate
>> paragraph for the IndexedFaceSet, which commences “If the *texCoord*
>> field is NULL, ….”. Here an implementation behaviour is detailed for when
>> the default value is NULL. In comparison, the IndexedTriangleSet node has
>> no such behaviour defined.
>> 
>> 
>> 
>> I don’t know why the two instances are different. It is an interesting
>> observation., which is also worthy of a specification comment.
>> 
>> 
>> 
>> Regards,
>> 
>> 
>> 
>> Roy
>> 
>> 
>> 
>> *From:* x3d-public [mailto:x3d-public-bounces at web3d.org] *On Behalf Of *Andreas
>> Plesch
>> *Sent:* 11 April 2016 14:34
>> *To:* X3D Graphics public mailing list
>> *Subject:* [x3d-public] IndexedTriangleSet defaults
>> 
>> 
>> 
>> For IndexedTriangleSet the default value for texCoord is NULL.
>> 
>> 
>> http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/rendering.html#IndexedTriangleSet
>> 
>> On the other hand the texCoord default value for IndexedFaceSet is a
>> reasonable map which tries to fit a texture on the mesh.
>> 
>> Is there a reason for this divergence ?
>> 
>> Andreas
>> 
> 
> 
> 
> -- 
> Andreas Plesch
> 39 Barbara Rd.
> Waltham, MA 02453
> 
> 
> 
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