[x3d-public] InlineGeometry node and PLY format support in Castle Game Engine
John Carlson
yottzumm at gmail.com
Mon Apr 6 11:47:57 PDT 2026
Sorry I meant I was able to see black point clouds without color (Michalis
apparently uses different properties?).
On Mon, Apr 6, 2026 at 1:00 PM John Carlson <yottzumm at gmail.com> wrote:
> I agree that the PLYs that I worked with weren’t suitable for X3D. Either
> my parser was off, or there were negative color values, negative scales
> etc. I thought a second person could look at the same files and make
> better progress. I was able to view black points clouds (no clouds) from
> the PLY files in castle. I can probably change the property in the PLY
> file to achieve color in the point cloud. The point is, I don’t know if
> there’s standard PLY color properties.
>
> Thanks,
>
> John
>
> On Mon, Apr 6, 2026 at 12:18 AM Don Brutzman <don.brutzman at gmail.com>
> wrote:
>
>> Thank you Michalis for implementing the draft InlineGeometry node.
>> Having both Castle Game Engine and (already supporting)
>> X_ITE/Playground/Sunrize is definitely accelerating our design,
>> implementation and evaluation of LOA-5 bone segments for HAnim. Tests of
>> your Castle Model Viewer beta release look good on this end.
>>
>> Repeating a prior reply: "Gaussian Splat PLYs" (whatever that means)
>> does not seem like a good use of effort. There is a lot of ongoing
>> developmental work on gaussian splat formats by various companies that are
>> nonstandard, inconsistent, possibly unstable, and often proprietary. Some
>> happen to use .ply as a container. A prudent approach is to wait and see
>> what glTF does once things stabilize. Using Inline with glTF 2.0 (in json
>> or glb) is already in X3D 4.0, extension support by browsers is optional,
>> so that is a reasonable future path if consensus ever emerges.
>>
>> The draft X3D specification for InlineGeometry describes rationale and
>> includes references for the PLY format.
>>
>> - X3D Architecture 4.1 draft — ISO/IEC 19775-1:202x — 9 Networking
>> component
>> <https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/networking.html#InlineGeometry>
>> 9.4.3 InlineGeometry
>> <https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/networking.html#InlineGeometry>
>> -
>> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/networking.html#InlineGeometry9.4.3
>> InlineGeometry
>>
>> InlineGeometry : X3DGeometryNode, X3DUrlObject {
>> SFTime [in,out] autoRefresh 0.0 [0,infinity)
>> SFTime [in,out] autoRefreshTimeLimit 3600.0 [0,infinity)
>> SFString [in,out] description ""
>> SFBool [in,out] load TRUE
>> SFNode [in,out] metadata NULL [X3DMetadataObject]
>> MFString [in,out] url [] [URI]
>> }
>>
>> InlineGeometry loads geometry from an external file. The result
>> provides a polygonal mesh, set of lines, point cloud, parametric surface,
>> or other geometry.
>>
>> The *url* field can support loading a variety of file formats
>> defining polygonal mesh geometry. When the *url* field contains no
>> values ([]), no default geometry is provided. Required Recommended support
>> by X3D browsers includes both ASCII and binary encodings for the STL format
>> (see STL
>> <https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/bibliography.html#STL>)
>> as well as the PLY polygonal geometry format (see PLY
>> <https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/bibliography.html#PLY>),
>> respectively. Other file types can be optionally supported by a browser.
>> TODO: consider "required support" of STL/PLY formats rather than
>> "recommended support" since numerous open-source conversion implementations
>> are available, no IPR considerations pertain, and STL/PLY formats are the
>> primary use case.
>>
>> If the *url* field refers to an X3D file or a VRML97 file, the first
>> geometry node found in that file (excluding both prototype declarations and
>> prototype instances) is used to provide the InlineGeometry contents. X3D
>> browsers shall recognize *url* fields that end with "#*DEFname*" to
>> mean the geometry node with DEF label of *DEFname* in the given X3D
>> or VRML97 file.
>>
>> The run-time system can support any number of 3D model resource types
>> as long as those follow the available Model Primary Content Type for
>> Multipurpose Internet Mail Extensions (MIME) model definition (see
>> RFC2077
>> <https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/references.html#RFC2077>),
>> provide a registered content type (e.g., model/stl, text/plain etc.)
>> (see IANA_MEDIA
>> <https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/references.html#IANA_MEDIA>
>> and IANA_STL
>> <https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/references.html#IANA_STL>),
>> and can be determined with some form of content negotiation (see
>> RFC9110
>> <https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/references.html#RFC9110>).
>> Support is recommended for both text and binary encodings associated with a
>> given model format, when so defined.
>>
>> NOTE Experimental variations of PLY format used for Gaussian Splat
>> rendering are not expected for InlineGeometry. Such capabilities are better
>> supported by Inline node loading of glTF models.
>>
>> EXAMPLES
>>
>> Shape {
>> geometry InlineGeometry { url [ "MyFavoriteMesh.stl" ] }
>>
>> appearance USE FancyPaintAppearance # previously defined
>> }
>>
>> Shape {
>> geometry InlineGeometry { url [ "HelloWorld.x3d#TextMessage" ] }
>>
>> appearance USE FancyPaintAppearance # previously defined
>> }
>>
>> Editors notes.
>> - Are better authoritative references possible for STL and PLY? See Mantis
>> 1522 <https://mantis.web3d.org/view.php?id=1522>.
>> - InlineGeometry results differ from an Inline node, which
>> produces an X3DChildNode scene subgraph implementing the X3DBoundedObject
>> interface. An Inline node cannot be used as the *geometry* field
>> of a Shape.
>> - Results from browser loading may be any kind of polygonal mesh
>> or parametric surface (e.g. IndexedFaceSet, TriangleSet, Extrusion, etc.)
>> but cannot be further manipulated or animated by events from the scene.
>> - Direct loading of such geometry files eliminates the need for
>> prior model conversion into X3D, and adds flexibility when applying
>> Appearance to the result.
>> - The "#*DEFname*" syntax directly matches EXTERNPROTO URL
>> semantics
>> <https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/concepts.html#EXTERNPROTOURLSemantics> considerations.
>> Not requiring IMPORT/EXPORT statements provides greater backwards
>> compatibility with legacy models, avoiding unnecessary complications and
>> possible ambiguity.
>> - Composition of online addresses and parameter values within a
>> *url* field offers the possibility of invoking an online server to
>> perform file-format conversions. See email thread [x3d-public]
>> Inline > type field > for loading / converting / parsing other content
>> <https://web3d.org/pipermail/x3d-public_web3d.org/2026-March/022355.html> for
>> further discussion. Such additional functionality supports the use cases
>> under consideration by Metaverse Standards Forum (MSF) 3D Web
>> Interoperability
>> <https://metaverse-standards.org/domain-groups/3d-web-interoperability> Working
>> Group.
>>
>>
>> Worth reading: the original PLY definition first defined in 1994 by Greg
>> Turk at Stanford University., references above.
>>
>> - [PLY
>> <https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD/Part01/bibliography.html#PLY>
>> ]
>> -
>> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD/Part01/bibliography.html#PLY
>> - Wikipedia, PLY (file format), 26 February 2026.
>> https://en.wikipedia.org/wiki/PLY_(file_format)
>>
>> and
>>
>> 1. Greg Turk. "The PLY Polygon File Format"
>> <https://web.archive.org/web/20161204152348/http://www.dcs.ed.ac.uk/teaching/cs4/www/graphics/Web/ply.html>.
>> Archived from the original
>> <http://www.dcs.ed.ac.uk/teaching/cs4/www/graphics/Web/ply.html> on
>> 2016-12-04.
>> 2. Greg Turk. "The PLY Polygon File Format (extended)"
>> <https://gamma.cs.unc.edu/POWERPLANT/papers/ply.pdf> (PDF).
>>
>> and
>>
>> - PLY - Polygon File Format <https://paulbourke.net/dataformats/ply/>
>> https://paulbourke.net/dataformats/ply
>>
>> Improvements to draft specification, especially with implementation and
>> evaluation, are always welcome.
>>
>> all the best, Don
>> --
>> X3D Graphics, Maritime Robotics, Distributed Simulation
>> Relative Motion Consulting https://RelativeMotion.info
>>
>>
>> On Sun, Apr 5, 2026 at 6:39 PM John Carlson via x3d-public <
>> x3d-public at web3d.org> wrote:
>>
>>> Hi, Michalis, Seeing Gaussian Splat PLYs renderered with humanoid
>>> animation would be cool to see. With your expertise in binary formats and
>>> binary PLY, probably an easy next step!
>>>
>>> John
>>>
>>> On Sun, Apr 5, 2026 at 8:05 PM Michalis Kamburelis via x3d-public <
>>> x3d-public at web3d.org> wrote:
>>>
>>>> With big thanks to Don who provided information and pushed me to
>>>> implement it!:)
>>>>
>>>> 1. We support now InlineGeometry in Castle Game Engine and Castle
>>>> Model Viewer.
>>>>
>>>> - I tested on a few examples, and made our own:
>>>> https://github.com/castle-engine/demo-models/tree/master/x3d/inline_geometry
>>>>
>>>> - You can refer to a geometry from any model format we support,
>>>> including X3D, glTF, STL, PLY...:
>>>> https://castle-engine.io/model_formats
>>>>
>>>> 2. We support now loading models in a PLY format.
>>>>
>>>> - ASCII and binary versions.
>>>>
>>>> - Faces or without faces (point cloud, i.e. just our PointSet).
>>>>
>>>> - Testcases include
>>>> https://github.com/castle-engine/demo-models/tree/master/ply and
>>>> https://sketchfab.com/3d-models/kaktus-ply-7b7cc7188f17468595506500e186a9c0
>>>> .
>>>>
>>>> More information and screenshots about both features in our news post
>>>> on
>>>> https://castle-engine.io/wp/2026/04/06/support-for-ply-model-format-and-inlinegeometry-node/
>>>> .
>>>>
>>>> They are available to test right now if you download
>>>> - the "snapshot" version of Castle Model Viewer
>>>> https://castle-engine.io/castle-model-viewer
>>>> - or full engine from https://castle-engine.io/download .
>>>>
>>>> Regards,
>>>> Michalis
>>>>
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>>
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