[x3d-public] X3DParticleEmitter node inherit fromX3DChildNode(ratherthan X3DNode)

[Joseph D Williams]

➢ decision was deliberate but cannot speak to the specific motivation

can be a structure where the meta describes the environment and then encloses some user code. Usefull in the authoring environment as filter for structure and values?  In both we strip the meta to get the user code runtime, just that in X3D the meta is info about the containing node that may be useful at import but has no bearing at runtime. Also, I can just imagine reading the stuff if every node could have a meta dad. Maybe the only exception is for a scene root level meta to hold the scene and contain all the search code works for the particular root node or other context. For example this would replace or encase the lines of name-value pairs in the head,.
Thanks 
Joe

From: Andreas Plesch
Sent: Thursday, March 10, 2022 1:08 PM
To: Joseph D Williams
Cc: Brutzman, Donald (Don) (CIV); X3D Graphics public mailing list
Subject: Re: [x3d-public] X3DParticleEmitter node inherit fromX3DChildNode(ratherthan X3DNode)

Good comments.
• MetadataSet to have X3DNode nodes 
If I understand it, the idea of ending meta to include actual user code for the scenegraph is exactly the sort of extension wanting to be “worthwhile to deviate a bit and be more permissive than the spec” that dooms the long-term validation operation. Maybe good for something with simple structure that looks convenient and logical and seemingly convenient to implement at first thought and elementary usage, then ends up making something definitely not to be best practice. Please delineate the “worthwhile” parts that make a case.

I only know that this construction shows up in most of x-ite examples, and is how the Titania editor saves a scene, simple or complex. I can only deduce that this decision was deliberate but cannot speak to the specific motivation by the author. Speculating, the feature seems to be valuable for authoring. It should be possible to convert to standard x3d automatically by moving the DEF node from the MetadataSet to the first USE node, perhaps by xslt.

Not quite sure how validation would be affected.

I agree that Metadata nodes should be limited to actual metadata but a library node seems sensible.

Here is a list of other, well established scene graph systems which do have a concept of a non-renderable library which is separate and can then be referenced as needed:

- svg
- glTF
- a-frame
- collada (I believe)

it is a natural concept and perhaps allows for cleaner user code organization. Having two alternative ways to define a DEF node (in a library, and as a first scene graph node) does seem to invite friction, and would need to be carefully considered.

Andreas

 
From: Andreas Plesch
Sent: Tuesday, March 8, 2022 11:39 AM
To: Brutzman, Donald (Don) (CIV)
Cc: X3D Graphics public mailing list
Subject: Re: [x3d-public] X3DParticleEmitter node inherit fromX3DChildNode(rather than X3DNode)
 
Yes, I am pretty sure Holger is aware. I only brought it up because Titania/x-ite typically stays very close to the spec. But this is a capability where Titania/x-ite found it worthwhile to deviate a bit and be more permissive than the spec. This decision may point to the value of having a way to DEF any X3DNode (not just child nodes) outside of the scene graph, outweighing strict compliance.
 
All the best, Andreas
 
On Tue, Mar 8, 2022 at 2:22 PM Brutzman, Donald (Don) (CIV) <brutzman at nps.edu> wrote:
MetadataSet is only allowed to contain other Metadata* nodes or comments.  Other content will fail validation (and will not load or import in the X3DJSAIL Java and X3DPSAIL Python libraries).
 
The right way to cache non-rendered content for DEF/USE libraries is to put them as children nodes within a Switch node with whichChoice=’-1’.
 
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 Andreas Plesch
Sent: Tuesday, March 8, 2022 10:11 AM
To: X3D Graphics public mailing list <x3d-public at web3d.org>
Subject: Re: [x3d-public] X3DParticleEmitter node inherit from X3DChildNode(rather than X3DNode)
 
Of note is that Titania and x-ite allow MetadataSet to have X3DNode nodes, eg. any node, in the value field, not just X3DMetadataObject nodes.
 
This allows MetadataSet to be used as a NodesLibrary for DEF/USE purposes. In fact, this kind of redirection is the default setup for scenes created in Titania.
 
SVG also has a NodesLibrary equivalent, the <defs> element:
 
https://developer.mozilla.org/en-US/docs/Web/SVG/Element/defs
 
-Andreas
 
Date: Mon, 7 Mar 2022 21:29:41 +0100
From: Michalis Kamburelis <michalis.kambi at gmail.com>
To: Joseph D Williams <joedwil at earthlink.net>
Cc: GPU Group <gpugroup at gmail.com>,  "X3D Public Mailing List
        (x3d-public at web3d.org)" <x3d-public at web3d.org>
Subject: Re: [x3d-public] X3DParticleEmitter node inherit from
        X3DChildNode(rather than X3DNode)
Message-ID:
        <CAKzBGZNToR-7CmaUzRxBE3xx9J6j2mPgmvKAjQKpGQxjdY_0hA at mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"

Perhaps I should have written

"""
The nodes within NodesLibrary don't make any effect, they are not
traversed. They are only to be reUSEd (referenced) by other parts of
the graph."
"""

This makes the wording consistent with how e.g. Switch is described.
Sure you have all the nodes in memory, you just don't traverse to
inactive parts of Switch, LOD, NodesLibrary etc.

Regards,
Michalis


 
-- 
Andreas Plesch
Waltham, MA 02453
 



-- 
Andreas Plesch
Waltham, MA 02453

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