[x3d-public] alphaMode Tangent example, AlphaBlendModeTest.x3d

[Don Brutzman]

p.s. I tracked down Appearance.alphaMode, apologies had forgotten that we
indeed added it to X3D 4.0.

   - X3D Architecture version 4.0, clause 12 Shape component, 12.4.2
   Appearance
   -
   https://www.web3d.org/specifications/X3Dv4/ISO-IEC19775-1v4-IS/Part01/components/shape.html#Appearance
   -
   https://www.web3d.org/x3d/tooltips/X3dTooltips.html#Appearance.alphaMode

Appearance : X3DAppearanceNode {
>   SFNode   [in,out] acousticProperties NULL   [AcousticProperties]  SFFloat  [in,out] alphaCutoff        0.5    [0,1]
>   SFString [in,out] alphaMode          "AUTO" ["AUTO", "OPAQUE", "MASK", "BLEND"]
>   SFNode   [in,out] backMaterial       NULL   [X3DOneSidedMaterialNode]
>   SFNode   [in,out] fillProperties     NULL   [FillProperties]
>   SFNode   [in,out] lineProperties     NULL   [LineProperties]
>   SFNode   [in,out] material           NULL   [X3DMaterialNode]
>   SFNode   [in,out] metadata           NULL   [X3DMetadataObject]
>   SFNode   [in,out] pointProperties    NULL   [PointProperties]
>   MFNode   [in,out] shaders            []     [X3DShaderNode]
>   SFNode   [in,out] texture            NULL   [X3DTextureNode]
>   SFNode   [in,out] textureTransform   NULL   [X3DTextureTransformNode]
> }
>
> and we have an example:

   - X3D Example Archives: X3D4AM, X3D for Advanced Modeling, Gltf Sample
   Models, Alpha Blend Mode Test
   - This model tests the various alpha modes available in glTF 2.0
   rendering. There are three settings for alphaMode: "OPAQUE" (the default),
   "BLEND", and "MASK". Of these, "MASK" takes an additional alphaCutoff value
   that modifies it.
   -
   https://www.web3d.org/x3d/content/examples/X3dForAdvancedModeling/GltfSampleModels/AlphaBlendModeTestIndex.html

Interestingly, our 2024 version had Tangent nodes included and commented
out... I have restored them and updated the model to X3D version 4.1.  Also
applied DEF/USE on various image textures.  Also handled flipVertically by
inserting One of the tangent nodes has a problem.  from latest draft
X3D-Edit Validator:

Performing X3D Schematron check...
> X3D version 4.1 began active development by Web3D Consortium for ISO in
> 2025.[/X3D, diagnostic]
> Based on file name, AlphaBlendModeTest.x3d is considered a test model
> supporting X3D Quality Assurance (QA).
>
> https://www.web3d.org/x3d/content/examples/X3dResources.html#QualityAssurance
> [/X3D/head, diagnostic]
> <meta name='warning' content='removed gravityTransform=false since this
> construc is not valid X3D4. several converters not yet supporting Tangent
> node properly, perform QA checks for details.'/> [/X3D/head/meta[6],
> diagnostic]
> <Tangent DEF='TodoFigureOutMissingValue'/> vector array has 6.75 4-tuples,
> likely has incorrect number of values or missing whitespace
> [/X3D/Scene/Transform[1]/Group/Shape/IndexedTriangleSet/Tangent, warning]
>
> --------- X3D Validator checks complete for AlphaBlendModeTest.x3d
> ---------
>

X_ITE looks good, pretty close to the reference image at

   -
   https://github.com/KhronosGroup/glTF-Sample-Models/tree/main/2.0/AlphaBlendModeTest

Castle is mostly rendering correctly but has unhappy textures with
the broken Tangent node, reporting

2 warnings:
> VRML/X3D: Error when reading field "vector" value: Error at line 1 column
> 360: Expected float number, got end of stream
> X3D: Invalid number of items in an attribute array for shape
> "Bed/BedMesh//IndexedTriangleSet": Not enough items in tangents: 54, but at
> least 72 required
> Scene URL: "file:///C:/x3d-code/
> www.web3d.org/x3d/content/examples/X3dForAdvancedModeling/GltfSampleModels/AlphaBlendModeTest.x3d
> ".
> Use "File->View Warnings" menu to view these warnings again.
>

Model now updated online.  If someone can figure out the missing Tangent
vector values from the original glTF, that might fix the remaining gaps...

   - X3D Model Documentation AlphaBlendModeTest.x3d (X3dToXhtml listing)
   <https://www.web3d.org/x3d/content/examples/X3dForAdvancedModeling/GltfSampleModels/AlphaBlendModeTest.html#TodoFigureOutMissingValue>
   -
   https://www.web3d.org/x3d/content/examples/X3dForAdvancedModeling/GltfSampleModels/AlphaBlendModeTest.html#TodoFigureOutMissingValue
   - <Tangent DEF='TodoFigureOutMissingValue' vector='0.999847650527954
   -0.0174568109214306 0 0.999847650527954 -0.0174568109214306 0
   0.999847650527954 -0.0174568109214306 0 0.999847650527954
   -0.0174568109214306 0 0.999847650527954 -0.0174568109214306 0
   0.999847650527954 -0.0174568109214306 0 0.999847650527954
   -0.0174567885696888 0 0.999847650527954 -0.0174567885696888 0
   0.999847650527954 -0.0174567885696888 0'/>

Looking at things like this is a pretty good way to learn how things work.
Have fun with X3D!  🤔 👍

all the best, Don
-- 
X3D Graphics, Maritime Robotics, Distributed Simulation
Relative Motion Consulting  https://RelativeMotion.info
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