[x3d-public] IndexedTriangleSet defaults

Behr, Johannes johannes.behr at igd.fraunhofer.de
Thu May 5 01:45:06 PDT 2016


What's wrong about the TextureCoordinateGenerator ?!?

 http://www.web3d.org/documents/specifications/19775-1/V3.3/index.html

http://doc.x3dom.org/developer/x3dom/nodeTypes/TextureCoordinateGenerator.html

Best regards
Johannes

> On 2 May 2016, at 06:29, John Carlson <yottzumm at gmail.com> wrote:
> 
> 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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