[x3d-public] 3D graphics, vertex attributes Tangent index and vector

John Carlson yottzumm at gmail.com
Sat May 17 13:15:38 PDT 2025 

Please review Michalis’ response on this thread about tangentIndex and
tangentPerVertex.  I believe the corresponding normal fields apply.

Level 5? That depends on updated standard.

On Sat, May 17, 2025 at 2:04 PM Joe D Williams <joedwil at earthlink.net>
wrote:

> * must have tangentIndex (unless tangentIndex same as normalIndex).
>
> * If no tangentIndex, coordIndex used?
>
> * tangentPerVertex? Can tangent be applied to vertex or face (like normal
> and color)?
>
> * must have tangent vector (may be auto filled).
>
> * Level 5 required since level 4 does not have tangent.
>
> Thanks,
>
> Joe
>
>
>
> -----Original Message-----
> From: John Carlson <yottzumm at gmail.com>
> Sent: May 16, 2025 10:32 PM
> To: Extensible 3D (X3D) Graphics public discussion <x3d-public at web3d.org>
> Cc: Joe D Williams <joedwil at earthlink.net>
> Subject: Re: [x3d-public] 3D graphics, vertex attributes Tangent index and
> vector
>
>
> Joe,
>
> X_ITE IFS:
>
> https://create3000.github.io/x_ite/components/geometry3d/indexedfaceset/
>
> Summary, only tangent field.
> John
>
> On Fri, May 16, 2025 at 8:59 PM Joe D Williams via x3d-public <
> x3d-public at web3d.org> wrote:
>
>> like  for normals, is there a tangentPerVertex true/false where tangent
>> value
>>
>> is associated with vertex or face?
>>
>> If tangentIndex null, is coordIndex used?
>>
>> If Tangent vector null tangents are generated after Normal vector?
>>
>>
>>
>> Thanks,
>>
>> Joe
>>
>>
>>
>>
>>
>>
>>
>> -----Original Message-----
>> From: Extensible 3D (X3D) Graphics public discussion <
>> x3d-public at web3d.org>
>> Sent: May 15, 2025 6:19 AM
>> To: X3D <x3d-public at web3d.org>
>> Cc: Holger Seelig <holger.seelig at yahoo.de>
>> Subject: Re: [x3d-public] 3D graphics, vertex attributes Tangent index
>> and vector
>>
>>
>> There are also glTF tests for tangents:
>>
>> Geometry with tangent node:
>>
>> https://create3000.github.io/x_ite/laboratory/gltf-sample-viewer/?url=https://raw.githubusercontent.com/KhronosGroup/glTF-Sample-Models/master/2.0/NormalTangentMirrorTest/glTF/NormalTangentMirrorTest.gltf
>>
>> Geometry without tangent node (auto generated tangents using MikkTSpace
>> algorithm):
>>
>> https://create3000.github.io/x_ite/laboratory/gltf-sample-viewer/?url=https://raw.githubusercontent.com/KhronosGroup/glTF-Sample-Models/master/2.0/NormalTangentTest/glTF/NormalTangentTest.gltf
>>
>> The reflection in all half spheres should look the same.
>> Turn on IBL (Image Based Lighting).
>>
>> Best regards,
>> Holger
>>
>> --
>> Holger Seelig
>> Leipzig, Germany
>>
>> holger.seelig at yahoo.de
>> https://create3000.github.io/x_ite/
>> https://patreon.com/X_ITE
>>
>>
>> Am 15.05.2025 um 10:35 schrieb Holger Seelig via x3d-public <
>> x3d-public at web3d.org>:
>> All nodes which have a normal field also have a tangent field in X_ITE,
>> because tangents are very important for PhysicalMaterial to render
>> correctly. Because tangents always come in conjunction with normals,
>> normalPerVertex field is also used for tangents.
>>
>> If there is no Tangent node, the MikkTSpace algorithm is used to generate
>> tangent vectors, as need by the glTF specification.
>>
>> If there is a Tangent node and the vector field is empty, results are
>> undefined.
>>
>> Tangent node:
>> https://create3000.github.io/x_ite/components/rendering/tangent/
>>
>> IndexedFaceSet with tangent field:
>>
>> https://create3000.github.io/x_ite/components/geometry3d/indexedfaceset/#fields-tangent
>>
>> Best regards,
>> Holger
>>
>> --
>> Holger Seelig
>> Leipzig, Germany
>>
>> holger.seelig at yahoo.de
>> https://create3000.github.io/x_ite/
>> https://patreon.com/X_ITE
>>
>>
>> Am 15.05.2025 um 10:24 schrieb Michalis Kamburelis <
>> michalis.kambi at gmail.com>:
>> I don't know about Tangent in X_ITE...
>>
>> But in Castle Game Engine we have a similar extension -- Tangent node (
>> https://castle-engine.io/x3d_implementation_rendering_extensions.php ).
>> Looks like we developed it independently from X_ITE :) It certainly makes
>> sense to have a node that carry this information, to have perfect
>> rendering. (Tangents can be auto-calculated, but there are various details
>> in the auto-calculation algorithm that various renderers may do a bit
>> differently. When the 3D author used "baking" to make a normalmap texture,
>> it's better to use exact same tangents as known by the 3D authoring tool.)
>>
>> At least for Castle Game Engine, the answer is: if the Tangent node is
>> not present, but we need tangents (e.g. for bump mapping), then the tangent
>> vectors are calculated to match the normal vectors. So there's no
>> additional tangentPerVertex or tangentIndex, they would not make sense. By
>> knowing the normal vectors, by know all we need to generate reasonable
>> tangent vectors.
>>
>> See https://castle-engine.io/x3d_implementation_rendering_extensions.php
>> for more details.
>>
>> Regards,
>> Michalis
>>
>> czw., 15 maj 2025 o 07:43 John Carlson via x3d-public <
>> x3d-public at web3d.org> napisał(a):
>>
>>> Note, it’s Tangent vector=… not Tangent point=…
>>>
>>> John
>>>
>>> On Thu, May 15, 2025 at 12:38 AM John Carlson <yottzumm at gmail.com>
>>> wrote:
>>>
>>>> I’d ask Holger, cc’d
>>>>
>>>> I’ve not used Tangent, myself.
>>>>
>>>> X_ITE Supports up to Level 4, so I guess you’re proposing a new level 5
>>>> for the Geometry 3D component?
>>>>
>>>> Look at X_ITE IFS:
>>>>
>>>> <IMG_0516.png>
>>>>
>>>> Maybe check Holger’s create3000 Library for examples?
>>>>
>>>> To retrieve examples, last time I tried:
>>>>
>>>> git clone https://github.com/create3000/Library
>>>> Online at:
>>>>
>>>> https://github.com/create3000/Library
>>>> Let’s get v2 Joe Kick out the door, check v2 finger joints, and make
>>>> sure all joints have converted to v2.
>>>>
>>>> John
>>>>
>>>> On Wed, May 14, 2025 at 10:45 PM Joe D Williams <joedwil at earthlink.net>
>>>> wrote:
>>>>
>>>>>
>>>>> Main questions, in IFS Level5:
>>>>> Is a default tangent generated if Tangent point="" field empty?
>>>>> tangentPerVertex? assigned to vertex or face?
>>>>> tangentIndex? If no tangentIndex is coordIndex used?
>>>>>
>>>>>
>>>>> Thanks,
>>>>> Joe
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> -----Original Message-----
>>>>> From: John Carlson <yottzumm at gmail.com>
>>>>> Sent: May 14, 2025 3:00 PM
>>>>> To: Extensible 3D (X3D) Graphics public discussion <
>>>>> x3d-public at web3d.org>
>>>>> Cc: Joe D Williams <joedwil at earthlink.net>
>>>>> Subject: Re: [x3d-public] 3D graphics, vertex attributes
>>>>>
>>>>>
>>>>> Joe,
>>>>>
>>>>> X_ITE has a tangent node:
>>>>>
>>>>> Tangent | X_ITE X3D Browser
>>>>> <https://create3000.github.io/x_ite/components/rendering/tangent/>
>>>>>
>>>>> Enjoy!
>>>>>
>>>>> John
>>>>>
>>>>> On Wed, May 14, 2025 at 4:46 PM Joe D Williams via x3d-public <
>>>>> x3d-public at web3d.org> wrote:
>>>>>
>>>>>> From this:
>>>>>>
>>>>>>
>>>>>> https://docs.google.com/document/d/1hCetnGIkut_dyt4mwkDSTNiLTbrVg1jLo_EArE74DRg/edit?tab=t.0
>>>>>>
>>>>>>
>>>>>> In 3D graphics, vertex attributes define per-vertex data necessary
>>>>>> for rendering, animation, shading, and so on.
>>>>>> These attributes include geometric properties such as
>>>>>> position, normal, tangents, texture mapping information (UV
>>>>>> coordinates),
>>>>>> shading data (vertex colors), and
>>>>>> deformation information (skinning weights and blend shapes).
>>>>>>
>>>>>>
>>>>>> In this discussion of vertex attributes, the only one I don't recall
>>>>>> seeing in X3D is tangent?
>>>>>>
>>>>>> Associated with this work:
>>>>>>
>>>>>> https://docs.google.com/spreadsheets/d/18d1qy4jx-d_kLsam-JQAzig23w7dTau0Moe7M32lVvk/edit?gid=0#gid=0
>>>>>>
>>>>>>
>>>>>> Thanks,
>>>>>> Joe
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> x3d-public mailing list
>>>>>> x3d-public at web3d.org
>>>>>> http://web3d.org/mailman/listinfo/x3d-public_web3d.org
>>>>>
>>>>>
>>>>>
>>>> _______________________________________________
>>> x3d-public mailing list
>>> x3d-public at web3d.org
>>> http://web3d.org/mailman/listinfo/x3d-public_web3d.org
>>
>> _______________________________________________
>> x3d-public mailing list
>> x3d-public at web3d.org
>> http://web3d.org/mailman/listinfo/x3d-public_web3d.org
>>
>>
>> _______________________________________________
>> x3d-public mailing list
>> x3d-public at web3d.org
>> http://web3d.org/mailman/listinfo/x3d-public_web3d.org
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://web3d.org/pipermail/x3d-public_web3d.org/attachments/20250517/1f4e2764/attachment-0001.html>

More information about the x3d-public mailing list