[x3d-public] 3D graphics, vertex attributes Tangent index and vector
John Carlson
yottzumm at gmail.com
Thu May 29 14:01:48 PDT 2025
Michalis,
There’s a “view3dscene” on this page:
https://github.com/michaliskambi/x3d-tests/wiki/Image-Based-Lighting-%28EnvironmentLight-node%29
Probably you want to update it.
If you want to look through all your documentation for view3dscene, try
grep -r
or in your doc folder:
find doc -type f | xargs grep view3dscene
grep -l will give you filenames.
:thumbsup:
Hopefully, I’m not viewing a cache.
John
On Thu, May 29, 2025 at 3:29 PM Michalis Kamburelis via x3d-public <
x3d-public at web3d.org> wrote:
> 1. I believe we talked about glTF lighting equations a few times already
> when talking about glTF :) Here's a bunch of information, most of it
> hopefully still up-to-date:
>
> - "What about lights?" at
> https://github.com/michaliskambi/x3d-tests/wiki/How-to-add-PBR-to-X3D%3F#what-about-lights
> - "Punctual lights" at
> https://github.com/michaliskambi/x3d-tests/wiki/Converting-glTF-to-X3D#punctual-lights
> - "Image Based Lighting (EnvironmentLight node)"
> https://github.com/michaliskambi/x3d-tests/wiki/Image-Based-Lighting-%28EnvironmentLight-node%29
>
> In short: The glTF spec itself doesn't have lights, but
> - KHR_lights_punctual defines "punctual" lights and
> - EXT_lights_image_based / KHR_environment_map define "environment" light.
> X3D is already aligned with the former, and our planned EnvironmentLight
> will align us with the latter as well.
>
> As for sentence "perhaps they are using WebGL specifications" -- note:
> there's nothing about lights in WebGL specs, the rendering API is not where
> you define lighting equations. WebGL, as well as all modern rendering APIs,
> just says "shaders define how things look".
>
> 2. The Tangent node doesn't need any change to light equations or prose,
> IMHO, so there's nothing necessary to do.
>
> Our X3D spec already says that normalTexture is in the tangent space. It
> is said at normalTexture fields in *Material nodes, it is also reiterated
> in the "Lighting" chapter,
> https://www.web3d.org/documents/specifications/19775-1/V4.0/Part01/components/lighting.html
> :
>
> """N = normalized normal vector at this point on geometry. [...] It is
> modified by the normalTexture providing normals in the tangent space (see
> X3DOneSidedMaterialNode definition)."""
>
> That's really all we need to say, IMHO :) "Tangent space" should be clear
> to people who know how does the bump mapping work, it's not specific to X3D
> or glTF.
>
> Regards,
> Michalis
>
> czw., 29 maj 2025 o 20:06 Brutzman, Donald (Don) (CIV) <brutzman at nps.edu>
> napisał(a):
>
>> Very good and thanks for explaining how backwards compatibility is not
>> really a problem.
>>
>> If we can express correct behavior succinctly in the specification prose,
>> without adding potential confusion of another new field, that is certainly
>> fine by me. Being explicit about backwards compatibility, when needed, is
>> important to include.
>>
>> Next worry: lighting equations. Not finding any in glTF 2.0
>> specification itself. Can we use the KHR extensions to give us proper
>> context when updating our lighting equations? Surprisingly am not finding
>> any in the following, perhaps they are using WebGL specifications?
>>
>>
>> - KHR_lights_punctual extensions
>> -
>> https://github.com/KhronosGroup/glTF/blob/main/extensions/2.0/Khronos/KHR_lights_punctual/README.md
>>
>>
>> p.s. hypothesis: am suspecting that glTF 2.0 avoidance of precision
>> lighting definitions has been the root cause of why glTF implementations
>> have long had much difficulty getting various implementations to achieve
>> consistent rendering results.
>>
>>
>> all the best, Don
>>
>> --
>>
>> Don Brutzman Naval Postgraduate School, Code USW/Br
>> brutzman at nps.edu
>>
>> Watkins 270, MOVES Institute, Monterey CA 93943-5000 USA
>> +1.831.656.2149
>>
>> X3D graphics, virtual worlds, navy robotics
>> https://faculty.nps.edu/brutzman
>>
>>
>>
>> ------------------------------
>> *From:* Michalis Kamburelis <michalis.kambi at gmail.com>
>> *Sent:* Thursday, May 29, 2025 10:10 AM
>> *To:* Brutzman, Donald (Don) (CIV) <brutzman at nps.edu>
>> *Cc:* Holger Seelig <holger.seelig at yahoo.de>; X3D <x3d-public at web3d.org>
>> *Subject:* Re: [x3d-public] 3D graphics, vertex attributes Tangent index
>> and vector
>>
>> Happy to see Tangent node being considered for X3D. If it will match
>> exactly the glTF spec and behavior (and thus X_ITE behavior, from what I
>> see), it will be good :)
>>
>> Just one comment to what Don wrote: ""so X3D would need a boolean field
>> such as "SFBool [in out] computeTangents FALSE" in order to maintain
>> backward compatibility, since we have never computed such tangents before.""
>>
>> - No, please don't add "computeTangents" :)
>>
>> - The implementation (of X3D, or any other 3D application doing bump
>> mapping) knows when it needs tangents. Namely: when doing bump mapping,
>> i.e. using XxxMaterial.normalTexture. And it *has* to compute them in such
>> cases (unless of course we provide them explicitly in the Tangent node).
>>
>> - So there is *no* moment when field like computeTangents would make
>> sense to be considered, by any implementation. In all cases, implementation
>> already knows whether it has to compute tangents or not, if it would not
>> compute them -> normal mapping would make no sense.
>>
>> - The sentence "since we have never computed such tangents before" is not
>> true. All existing X3D implementations (that
>> handle XxxMaterial.normalTexture) already compute tangents, I guarantee,
>> you just didn't know about it :)
>>
>> - The reason is that normal maps are specified in tangent space. (as we
>> explicitly say in X3D spec about normalTexture, "The normals are provided
>> in tangent space").
>>
>> Regards,
>> Michalis
>>
>> czw., 29 maj 2025 o 01:49 Brutzman, Donald (Don) (CIV) <brutzman at nps.edu>
>> napisał(a):
>>
>> Thanks for excellent explanations and example. Thanks also for
>> correcting my mistaken impressions of what was being considered, this is
>> far different than geometric similarities between normal vectors and
>> tangent planes/vectors.
>>
>> Dick and I were able to review this during today's meeting.
>>
>> Holger, for your CompareTangent.x3d example, is it possible to achieve a
>> similar (or identical) effect by solely using Normal vectors? Just
>> curious, since both are supported in glTF we do want to maintain visual
>> compatibility.
>>
>> Aligning with glTF 2.0 has always been part of our approved consensus
>> efforts for improving the X3D 4 Architecture specification.
>>
>> - X3D Version 4.0 Standard Overview
>> - http://www.web3d.org/x3d4
>> X3D Version 4.0 Standard Overview | Web3D Consortium
>> <http://www.web3d.org/x3d4>
>> The X3D ® version 4 (X3D4) Architecture Specification is a major
>> upgrade to the Extensible 3D (X3D) Graphics International Standard that
>> provides close support for the HTML5 Recommendation, Khronos glTF
>> Physically Based Rendering (PBR), Web Audio API, and MIDI 2.0, along with
>> numerous other features. Humanoid Animation 2.0 (HAnim2) is also fully
>> supported, including BVH-style motion animation.
>> www.web3d.org
>> **
>>
>>
>> So the next line of inquiry would appear to be how to best accomplish the
>> satisfactory addition of Tangents to X3D Architecture.
>>
>> For such an significant addition, typically we need
>>
>> 1. Rationale (align with glTF, perhaps multiple other good reasons
>> given)
>> 2. Draft specification prose, references
>> 3. Examples, multiple implementations
>>
>>
>> Presumably the addition of a Tangent node would go into
>>
>> - X3D Architecture version 4.1 (draft), clause 11, Rendering component
>> -
>> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html
>>
>> - Tangent node would be inserted as section 11.4.12, between PointSet
>> and TriangleFanSet
>> - Node signature definition, i.e. field names, types, accessTypes,
>> default values
>> - Presumably prose would be needed for a new section under concepts,
>> e.g. 11.2.2.6 Tangents. That description would also need to distinguish
>> how they are different from Normals.
>> - There is an abstract type for X3DNormalNode under
>> X3DGeometricPropertyNode, do we need something similar?
>> - What level is proposed for Table 11.2 — Rendering component support
>> levels ?
>>
>> - What nodes are expected to have tangent field added? Presumably
>> some, but not all, of the geometry nodes?
>> - Update to Concepts, 4.4.2.3 Interface Hierarchy
>> -
>> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/concepts.html#InterfaceHierarchy
>> - What changes are needed to lighting equations in clause 17
>> Lighting component
>> -
>> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/lighting.html
>> - For example, the lighting equations in 17.2.2.3 Common
>> definitions for all lighting models
>> -
>> https://www.web3d.org/specifications/X3Dv4/ISO-IEC19775-1v4-IS/Part01/components/lighting.html#LightingCommon
>>
>> - Is it possible when Normal-node 3-tuple vectors and Tangent-node
>> 4-tuple planes are used together (as in the CompareTangent.x3d example) is
>> it possible for contrary or contradictory field information to provided?
>> (It looks like glTF says that Tangent values are ignored if Normal values
>> aren't also supplied at the same time).
>> - What potential error conditions need to be noted?
>> - Are there any potential unexpected "side effects" or issues to
>> resolve when working through this careful due-diligence integration in the
>> X3D Architecture
>>
>>
>> We looked closely at glTF specification prose, and have some questions.
>>
>> -
>> https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html#meshes-overview
>> - glTF requires "When tangents are not specified, client
>> implementations *SHOULD* calculate tangents using default MikkTSpace
>> <https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html#mikktspace> algorithms
>> with the specified vertex positions, normals, and texture coordinates
>> associated with the normal texture." ... and so X3D would need a boolean
>> field such as "SFBool [in out] computeTangents FALSE" in order to maintain
>> backward compatibility, since we have never computed such tangents before.
>> - Are there _any_ light definitions whatsoever in glTF 2.0
>> specification proper? It looks like all three basic lights are in the
>> KHR_punctual extension (and still no baseline lighting equations seen).
>> -
>> https://github.com/KhronosGroup/glTF/blob/main/extensions/2.0/Khronos/KHR_lights_punctual/README.md
>>
>>
>> Thanks for considering the possibilities.
>>
>>
>> all the best, Don
>>
>> --
>>
>> Don Brutzman Naval Postgraduate School, Code USW/Br
>> brutzman at nps.edu
>>
>> Watkins 270, MOVES Institute, Monterey CA 93943-5000 USA
>> +1.831.656.2149
>>
>> X3D graphics, virtual worlds, navy robotics
>> https://faculty.nps.edu/brutzman
>>
>>
>>
>> ------------------------------
>> *From:* Holger Seelig <holger.seelig at yahoo.de>
>> *Sent:* Saturday, May 24, 2025 7:30 AM
>> *To:* X3D <x3d-public at web3d.org>
>> *Cc:* Brutzman, Donald (Don) (CIV) <brutzman at nps.edu>; Michalis
>> Kamburelis <michalis.kambi at gmail.com>
>> *Subject:* Re: [x3d-public] 3D graphics, vertex attributes Tangent index
>> and vector
>>
>> I have created a simple example file from a previous glTF to show what a
>> difference the correct tangents make.
>>
>> Both spheres have the same material with only a normal texture.
>>
>> On the left side you can see a sphere with correct tangents and on the
>> right side the same sphere with negated tangents.
>>
>> You can see in the wrong version that the curvatures of the wicker go
>> inwards. Which is definitely not intentional.
>>
>>
>> https://create3000.github.io/x_ite/playground/?url=https://create3000.github.io/Library/Tests/Components/Rendering/CompareTangent.x3d
>>
>> Best regards,
>> Holger
>>
>> --
>> Holger Seelig
>> Leipzig, Germany
>>
>> holger.seelig at yahoo.de
>> https://create3000.github.io/x_ite/
>> https://patreon.com/X_ITE
>>
>>
>>
>> Am 24.05.2025 um 04:41 schrieb Michalis Kamburelis via x3d-public <
>> x3d-public at web3d.org>:
>>
>> Don,
>>
>> Answering the """If there is a benefit for X3D scene graph having
>> tangent vectors, in particular for achieving some new flavor of
>> rendering or geometry representation that we can't already do, then
>> apologies but haven't heard it yet.""" :
>>
>> I mentioned this benefit (of knowing tangent vector values) in point 3
>> of my message. Now also on
>> https://github.com/michaliskambi/x3d-tests/wiki/Tangent-node-in-X3D ,
>> see there:
>>
>> """
>> Ultimately, the "perfect tangent value" is the one that was used to
>> bake the normalmaps. If the authoring tool (like Blender) that you
>> used to make normalmaps used a bit different algorithm to calculate
>> tangents than your renderer -> then the rendering of normalmaps will
>> be slightly "off".
>>
>> There's a nice screenshot in
>>
>> https://gamedev.stackexchange.com/questions/146855/how-do-you-compute-the-tangent-space-vectors-with-normals-given-in-the-mesh
>> , scroll to "There are multiple ways to generate tangent spaces for a
>> mesh, and not all of them agree on the result.". The screenshot there
>> shows subtle problems that result from having authoring tool and
>> renderer calculate a bit different tangent vectors.
>> """
>>
>> There is a really a good reason why glTF has them and why X_ITE and
>> Castle Game Engine have defined extensions to have them too :)
>> Simplifying the above explanation: one needs to have Tangent
>> information (provided in Tangent node, not auto-calculated), to use
>> the normalmap exactly like the 3D authoring tool that generated it
>> intended. I *did* mention it in the past from I recall, I did show the
>> screenshot from
>>
>> https://gamedev.stackexchange.com/questions/146855/how-do-you-compute-the-tangent-space-vectors-with-normals-given-in-the-mesh
>> already in 2 past threads on x3d-pubilc (in 2019 and 2022, looking at
>> gmail history :) ).
>>
>> Again, maybe I can explain it best on next Friday call, if you want.
>>
>> Regards,
>> Michalis
>>
>>
>> sob., 24 maj 2025 o 04:00 Brutzman, Donald (Don) (CIV)
>> <brutzman at nps.edu> napisał(a):
>>
>>
>> Thanks for extra references, interesting.
>>
>> To be clearer, I was referring to "capital-T" Tangent planes. We do have
>> one of those in ClippingPlane node, plane field.
>>
>> https://www.web3d.org/x3d/content/X3dTooltips.html#ClipPlane.plane
>>
>>
>> Yes, the slideset does seem to show that there is a lot of math to
>> convert a normal vector space to a tangent vector space, and vice versa.
>> No, a single normal vector is not fully convertible bidirectionally to a
>> single tangent vector, since a single tangent vector is only one of
>> infinite possible tangent vectors originating at the same origin point of a
>> Tangent plane.
>>
>> If there is a benefit for X3D scene graph having tangent vectors, in
>> particular for achieving some new flavor of rendering or geometry
>> representation that we can't already do, then apologies but haven't heard
>> it yet.
>>
>> We can easily imagine a wide class of difficult-to-debug errors emerging
>> in X3D content for authors, players, and converters alike if support for
>> both normal vectors and tangent vectors becomes necessary.
>>
>> p.s. looks like we also have mapped WebGL/glTF techniques using
>> normalTexture node, e.g.
>>
>> X3D 4.1 draft Architecture,12.4.5 Material
>>
>> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/shape.html#Material
>>
>> SFFloat [in,out] normalScale 1 [0, ∞)
>> SFNode [in,out] normalTexture NULL [X3DSingleTextureNode]
>> SFString [in,out] normalTextureMapping ""
>>
>> I hope that this deeper-dive into details is viewed as helpful and
>> constructive.
>>
>> There are many additional things we can be doing with X3D, and still a
>> lot of re-alignments to finish in the large family of X3D standards that
>> need updating for X3D 4.0 Architecture. I am confident that together we
>> will all stay focused primarily on the important things - and occasionally
>> on the cool things too! Onward we go together, with steady forward
>> momentum overall.
>>
>>
>> all the best, Don
>>
>> --
>>
>> Don Brutzman Naval Postgraduate School, Code USW/Br
>> brutzman at nps.edu
>>
>> Watkins 270, MOVES Institute, Monterey CA 93943-5000 USA
>> +1.831.656.2149
>>
>> X3D graphics, virtual worlds, navy robotics
>> https://faculty.nps.edu/brutzman
>>
>>
>>
>> ________________________________
>> From: Michalis Kamburelis <michalis.kambi at gmail.com>
>> Sent: Friday, May 23, 2025 3:16 PM
>> To: John Carlson <yottzumm at gmail.com>
>> Cc: Extensible 3D (X3D) Graphics public discussion <x3d-public at web3d.org>;
>> Joe D Williams <joedwil at earthlink.net>; Brutzman, Donald (Don) (CIV) <
>> brutzman at nps.edu>
>> Subject: Re: [x3d-public] 3D graphics, vertex attributes Tangent index
>> and vector
>>
>>
>>
>> John: I know, in math, in 3D, you generally speak about "tangent
>> planes" (
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FTangent&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200150881%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=xI7y0QYdIcPFZmWTtWOAardp6qBhkbiocWzLIaXZjyA%3D&reserved=0
>> <https://en.wikipedia.org/wiki/Tangent> ).
>>
>> The name "tangent vector" is just a shorthand for "vector lying on a
>> tangent plane". This is a standard for calling this value in the
>> context of bump mapping / normal maps.
>>
>> See e.g. glTF spec with useful definition (
>>
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fregistry.khronos.org%2FglTF%2Fspecs%2F2.0%2FglTF-2.0.html%23introduction-technical-terminology&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200184217%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=U1GB3CyxbVkqCeZ50pNY5IQZV%2F6UVeB3fuuHSLtaTtM%3D&reserved=0
>> <https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html#introduction-technical-terminology>
>> "2.2.3. Technical Terminology" ):
>>
>> """
>> tangent
>> A unit XYZ vector defining a tangential direction on the surface.
>> """
>>
>> There is also "tangent coordinate space". If you want to get dirty and
>> read about details, search for "tangent normal mapping":
>>
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Flearnopengl.com%2FAdvanced-Lighting%2FNormal-Mapping&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200208362%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=htRXtm4jbhI6G0U0pN09lsBB5IEHQ3EKIocm948xxp8%3D&reserved=0
>> <https://learnopengl.com/Advanced-Lighting/Normal-Mapping> ,
>>
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.cs.utexas.edu%2F~fussell%2Fcourses%2Fcs384g-spring2016%2Flectures%2Fnormal_mapping_tangent.pdf&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200227319%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=65d5bG5b5n5jGKSrKA93pYgnKlV2x2Weg7fsDqMEpX0%3D&reserved=0
>> <https://www.cs.utexas.edu/~fussell/courses/cs384g-spring2016/lectures/normal_mapping_tangent.pdf>
>> .
>>
>> Regards,
>> Michalis
>>
>> sob., 24 maj 2025 o 00:05 John Carlson <yottzumm at gmail.com> napisał(a):
>>
>>
>> Tangent planes seem more likely than tangent vectors, at least in 3D.
>>
>> Just a naming convention.
>>
>> John
>> On Fri, May 23, 2025 at 4:09 PM Michalis Kamburelis <
>> michalis.kambi at gmail.com> wrote:
>>
>>
>> Don: I don't think that this decision (to never support Tangent node
>> in X3D), is correct. I would actually say we should add Tangent to
>> X3D.
>>
>> Let me present a clear argument "why". I copied some of the reasoning
>> from mail below to
>>
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fmichaliskambi%2Fx3d-tests%2Fwiki%2FTangent-node-in-X3D&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200245004%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=iA1%2Bgoq%2B1GtvXZXMLzdiCDOHOdyQlD4%2FU5vkrA%2FpWs0%3D&reserved=0
>> <https://github.com/michaliskambi/x3d-tests/wiki/Tangent-node-in-X3D> ,
>> to have a future reference.
>>
>> 1. Current state: As of now, both X_ITE and Castle Game Engine have
>> extensions to define Tangent node.
>>
>> So we have invented the "Tangent" node independently in 2
>> implementations and, predictably, they are unfortunately
>> similar-but-not-exactly the same. Links from this thread, where you
>> can notice a difference:
>>
>> -
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcreate3000.github.io%2Fx_ite%2Fcomponents%2Frendering%2Ftangent%2F&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200266292%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=uC0HoQQvQ%2FqGeaKvwUMRLczWiuPy3k5uhNpzdTVkS4g%3D&reserved=0
>> <https://create3000.github.io/x_ite/components/rendering/tangent/> ,
>> -
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcastle-engine.io%2Fx3d_implementation_rendering_extensions.php%23section_ext_tangent&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200287350%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=%2FiuYgr866%2FE0qt88XbIqwT6TQf%2FpGnCdQ97ziF5myn0%3D&reserved=0
>> <https://castle-engine.io/x3d_implementation_rendering_extensions.php#section_ext_tangent>
>>
>> Also glTF format has them. See
>>
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fregistry.khronos.org%2FglTF%2Fspecs%2F2.0%2FglTF-2.0.html%23meshes-overview&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200304976%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=DWIIKDtB4VQQ6g3wx9MhIJtafyag%2FzCo4hqXwBokl%2BY%3D&reserved=0
>> <https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html#meshes-overview>
>> , information about "TANGENT".
>>
>> ( Holger, if you read this: I think I will change Castle Game
>> Engine's Tangent node in the future, to match better both X_ITE and
>> glTF, thus we will have matching definitions with X_ITE. Your approach
>> is better, Tangent.vector should be 4D. )
>>
>> 2. Tangents *do not* just repeat the same information as normal
>> vectors, DRY principle doesn't apply here. I.e. the tangent vectors
>> are *not* a replacement for knowing normal vectors (nor is the other
>> way around).
>>
>> And just because the model provides normal vectors -- doesn't
>> mean that tangent vectors are already precisely 100% determined.
>>
>> There are multiple similar algorithms to determine tangent
>> vectors. The normal vector alone doesn't yet define the tangent ->
>> because in a 3D space, if you have a normal vector -> you still have
>> infinite possible values for a vector "orthogonal to normal". So
>> tangent vectors are auto-calculated (when not explicitly provided) to
>> match the normal vectors, but *also* to match the texture coordinates
>> used for normal maps. There are edge-cases when it is just not obvious
>> what should be the "perfect tangent" so various implementations
>> (MikkTSpace is just one example) can do different things.
>>
>> 3. Ultimately, the "perfect tangent value" is the one that was used to
>> bake the normalmaps. If the authoring tool (like Blender) that you
>> used to make normalmaps used a bit different algorithm to calculate
>> tangents than your renderer -> then the rendering of normalmaps will
>> be slightly "off".
>>
>> There's a nice screenshot in
>>
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgamedev.stackexchange.com%2Fquestions%2F146855%2Fhow-do-you-compute-the-tangent-space-vectors-with-normals-given-in-the-mesh&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200321272%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=QTZ5yNrn7f9QO6013RvTKJM83RpbLp1g3o%2BTV%2Bow34Y%3D&reserved=0
>> <https://gamedev.stackexchange.com/questions/146855/how-do-you-compute-the-tangent-space-vectors-with-normals-given-in-the-mesh>
>> , scroll to "There are multiple ways to generate tangent spaces for a
>> mesh, and not all of them agree on the result.". The screenshot there
>> shows subtle problems that result from having authoring tool and
>> renderer calculate a *bit* different tangent vectors.
>>
>> So the perfect thing to do, from a renderer, is to *not* calculate
>> the tangent vectors, instead take the tangent vectors as provided by
>> the authoring tool. That exactly why glTF has tangents, and why X_ITE
>> and Castle Game Engine support them too -- we don't just discard
>> tangent values from glTF (only to auto-calculate them), we prefer to
>> take tangent values recorded in the 3D model, because this makes
>> really good rendering.
>>
>> See
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fmichaliskambi%2Fx3d-tests%2Fwiki%2FTangent-node-in-X3D&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200342653%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=I2JoFkHp6yUXifxdOtDNZn%2B%2FEw%2F6B6CUggprigS0Ymg%3D&reserved=0
>> <https://github.com/michaliskambi/x3d-tests/wiki/Tangent-node-in-X3D>
>> , which I just created -- it mostly copies what I said above.
>>
>> I hope this helps. I'll be happy to explain it better on next Web3d
>> Friday teleconference, if you're not tired of my talking :) I can show
>> how the normalmaps are actually created.
>>
>> Regards,
>> Michalis
>>
>>
>> pt., 23 maj 2025 o 21:03 Brutzman, Donald (Don) (CIV) via x3d-public
>> <x3d-public at web3d.org> napisał(a):
>>
>>
>> The X3D group has looked closely at Tangent options in the past and
>> decided not to support it. Instead we use Normal nodes, as ever.
>>
>> Of geometric note is that they are literally orthogonal and thus either
>> representation can be used to the other.
>>
>> You will not find Tangent node in the X3D specification.
>>
>> X3D 4.1 draft Architecture, Annex Z (informative) Version content
>>
>> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/versionContent.html
>>
>>
>> Note that the X_ITE documentation specifically notes that support in that
>> application is nonstandard.
>>
>>
>> SFNode [in, out] tangent NULL [Tangent] non-standard]
>>
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcreate3000.github.io%2Fx_ite%2Fcomponents%2Fgeometry3d%2Findexedfaceset%2F%23fields-tangent&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200365822%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=IsR1bELZd2JIdywMabYl4fETQB7Nj18xYLNYDuYiD%2BE%3D&reserved=0
>> <https://create3000.github.io/x_ite/components/geometry3d/indexedfaceset/#fields-tangent>
>>
>>
>> There is no issue with codebases adding functionality that might help
>> their capabilities - the X in X3D is extensible, after all - but anyone
>> putting a Tangent definition into an X3D model file is creating
>> nonstandard, invalid, noninteroperable content.
>>
>> Also please be aware that there is a serious design principle behind this
>> decision: DRY. Thus, a statement I don't expect to repeat: we do not
>> intend to consider Tangent support in future X3D specifications.
>>
>> Wikipedia: Don't repeat yourself
>>
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FDon%27t_repeat_yourself&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200388617%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=ArQcjgKedJw1nBDJMHn9IXWR8eCaaeK4byCx1Q1deMU%3D&reserved=0
>> <https://en.wikipedia.org/wiki/Don't_repeat_yourself>
>>
>>
>> And some "dry humor" on that page:
>>
>> The opposing view to DRY is called WET, a backronym commonly taken to
>> stand for write everything twice (alternatively write every time, we enjoy
>> typing or waste everyone's time).
>>
>>
>> Recommendations:
>>
>> if your model data is starting with tangent values (for whatever reason)
>> then convert them to normal vectors, and
>> stick with standard X3D for best results.
>>
>>
>> Have fun with normal X3D! 🙂
>>
>>
>> all the best, Don
>>
>> --
>>
>> Don Brutzman Naval Postgraduate School, Code USW/Br
>> brutzman at nps.edu
>>
>> Watkins 270, MOVES Institute, Monterey CA 93943-5000 USA
>> +1.831.656.2149
>>
>> X3D graphics, virtual worlds, navy robotics
>> https://faculty.nps.edu/brutzman
>>
>>
>>
>>
>> ________________________________
>> From: x3d-public <x3d-public-bounces at web3d.org> on behalf of Joe D
>> Williams via x3d-public <x3d-public at web3d.org>
>> Sent: Sunday, May 18, 2025 5:03 PM
>> To: John Carlson <yottzumm at gmail.com>
>> Cc: Joe D Williams <joedwil at earthlink.net>; Extensible 3D (X3D) Graphics
>> public discussion <x3d-public at web3d.org>
>> Subject: Re: [x3d-public] 3D graphics, vertex attributes Tangent index
>> and vector
>>
>> ok, seems like from what I can study so far,
>>
>> the first use of Tangent vector is authortime production of
>>
>> normalized Normal vector for vertex or face.
>>
>> The author is looking for relief effects (bumpmapping)
>>
>> that are produced by Tangent vector.
>>
>> This process (MikkTSpace algorithm) would fill Normal vector.
>>
>> This process of generating Normal vector space is called baking.
>>
>>
>>
>> For Level5 runtime,
>>
>> If Normal vector not null then used directly.
>>
>> If Normal vector null, then normals auto generated by creaseAngle
>>
>> If Tangent vector null, then nothing.
>>
>> If Level 5 and Tangent vector not null then possible relief effects
>>
>> using length of Tangent vector.
>>
>>
>>
>> No "bake" in runtime.
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> For runtime, the generated Normal vector is used and
>>
>> if Tangent vector is not null, for the author to produce relief effects
>>
>> using length of Tangent vector.
>>
>> Is that true?
>>
>>
>>
>>
>>
>>
>>
>> .
>>
>> For runtime
>>
>> -----Original Message-----
>> From: John Carlson <yottzumm at gmail.com>
>> Sent: May 17, 2025 1:15 PM
>> To: Joe D Williams <joedwil at earthlink.net>
>> Cc: Extensible 3D (X3D) Graphics public discussion <x3d-public at web3d.org>
>> Subject: Re: [x3d-public] 3D graphics, vertex attributes Tangent index
>> and vector
>>
>>
>>
>> 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://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcreate3000.github.io%2Fx_ite%2Fcomponents%2Fgeometry3d%2Findexedfaceset%2F&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200410801%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=3xDsuKcMJc87j2bLfU4KyNF3brsK3IbYL0CqwE8Quc4%3D&reserved=0
>> <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://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcreate3000.github.io%2Fx_ite%2Flaboratory%2Fgltf-sample-viewer%2F%3Furl%3Dhttps%3A%2F%2Fraw.githubusercontent.com%2FKhronosGroup%2FglTF-Sample-Models%2Fmaster%2F2.0%2FNormalTangentMirrorTest%2FglTF%2FNormalTangentMirrorTest.gltf&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200428820%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=PpWz8VSjvMhqqCEZJV4O4LvlGzFnG2eLGCNk5wbhH4M%3D&reserved=0
>> <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://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcreate3000.github.io%2Fx_ite%2Flaboratory%2Fgltf-sample-viewer%2F%3Furl%3Dhttps%3A%2F%2Fraw.githubusercontent.com%2FKhronosGroup%2FglTF-Sample-Models%2Fmaster%2F2.0%2FNormalTangentTest%2FglTF%2FNormalTangentTest.gltf&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200445874%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=DU2%2F7PgyUgyWqjqiAcJuw5G6ncNht9yPMBME0SudrrY%3D&reserved=0
>> <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://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcreate3000.github.io%2Fx_ite%2F&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200461168%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=XjmnXZ9c2Q8GbU%2F2E%2F57OT5BPf%2FOIDPEyMWaAIKk3l8%3D&reserved=0
>> <https://create3000.github.io/x_ite/>
>>
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatreon.com%2FX_ITE&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200476270%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=dnpHDXrPKsnrgHGgRtQcJJd2IZxprCViABurmJXB22E%3D&reserved=0
>> <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://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcreate3000.github.io%2Fx_ite%2Fcomponents%2Frendering%2Ftangent%2F&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200493482%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=55sK6dVEuZQzTVZXhZ8I%2F1DhNilNlfkn2XvvmBO0xUo%3D&reserved=0
>> <https://create3000.github.io/x_ite/components/rendering/tangent/>
>>
>> IndexedFaceSet with tangent field:
>>
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcreate3000.github.io%2Fx_ite%2Fcomponents%2Fgeometry3d%2Findexedfaceset%2F%23fields-tangent&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200513069%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=dgiBEyO2hhPqy1%2FT87BJTK%2BwdI%2BpPcwt2YYGxaIHp70%3D&reserved=0
>> <https://create3000.github.io/x_ite/components/geometry3d/indexedfaceset/#fields-tangent>
>>
>> Best regards,
>> Holger
>>
>> --
>> Holger Seelig
>> Leipzig, Germany
>>
>> holger.seelig at yahoo.de
>>
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcreate3000.github.io%2Fx_ite%2F&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200532049%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=7Ro1wWBaCc%2BvT6L99mV0McgUAgjn%2F0o4dYUiY2692ZQ%3D&reserved=0
>> <https://create3000.github.io/x_ite/>
>>
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatreon.com%2FX_ITE&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200551288%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=ZhfBNA1G7rY%2Bdue%2BiXb9EMFn3aXE54dde3KT8UaJNfs%3D&reserved=0
>> <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://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcastle-engine.io%2Fx3d_implementation_rendering_extensions.php&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200570539%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=Nlb39lRO2YzN2P0E4B5wUDtgnsGJ25vkYD0g%2BmFeDKg%3D&reserved=0
>> <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://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcastle-engine.io%2Fx3d_implementation_rendering_extensions.php&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200589324%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=Xx2qMsMjIU1cIZJPyGgF4c5rp48LmfqZHkjJ9S%2BK%2By4%3D&reserved=0
>> <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://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fcreate3000%2FLibrary&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200608115%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=JdzgrFdJEsyXix%2BW43%2B8MAU6a%2FFgIItVOPuhEt3mIX8%3D&reserved=0
>> <https://github.com/create3000/Library>
>> Online at:
>>
>>
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fcreate3000%2FLibrary&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200624853%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=Ge%2BkLU1GPoDGZG5wQSl5nGgWxSm0T4YFASJw6GwlgxU%3D&reserved=0
>> <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
>>
>> 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://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdocs.google.com%2Fdocument%2Fd%2F1hCetnGIkut_dyt4mwkDSTNiLTbrVg1jLo_EArE74DRg%2Fedit%3Ftab%3Dt.0&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200642079%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=%2FAuhyK7W2zDHaxy%2BMIRF07Ve94Y0A%2BWWb7OofVb05pY%3D&reserved=0
>> <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://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdocs.google.com%2Fspreadsheets%2Fd%2F18d1qy4jx-d_kLsam-JQAzig23w7dTau0Moe7M32lVvk%2Fedit%3Fgid%3D0%23gid%3D0&data=05%7C02%7Cbrutzman%40nps.edu%7C5010a47039124367feb708dd9a477d98%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638836355200662035%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C40000%7C%7C%7C&sdata=4MpB30vyAlH78SJUrim3wvgE5IAEuN1gnBqBjV%2FlAAY%3D&reserved=0
>> <https://docs.google.com/spreadsheets/d/18d1qy4jx-d_kLsam-JQAzig23w7dTau0Moe7M32lVvk/edit?gid=0#gid=0>
>>
>>
>> Thanks,
>> Joe
>>
>>
>> _______________________________________________
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>>
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