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%%% Title = "XR Macros" area = "Internet" workgroup = "Internet Engineering Task Force"

[seriesInfo] name = "XR-Macros" value = "draft-XRMACROS-leonvankammen-00" stream = "IETF" status = "informational"

date = 2023-04-12T00:00:00Z

author initials="L.R." surname="van Kammen" fullname="L.R. van Kammen"

%%%

.# Abstract

This draft offers a specification for embedding macros in existing 3D scenes/assets, to offer simple interactions and configure the renderer further.
Together with URI Fragments, it allows for rich immersive experiences without the need of a complicated sandboxed scripting languages.

Almost every idea in this document is demonstrated at https://xrfragment.org, as this spec was created during the XR Fragments spec.

{mainmatter}

Introduction

How can we add more features to existing text & 3D scenes, without introducing new dataformats?
Historically, there's many attempts to create the ultimate markuplanguage or 3D fileformat.
Their lowest common denominator is: (co)authoring using plain text.
Therefore, XR Macros allows us to enrich/connect existing dataformats, by offering a polyglot notation based on existing notations:

getting/setting common used 3D properties using querystring- or JSON-notation
targeting 3D properties using the lightweight query notation present in XR Fragments

NOTE: The chapters in this document are ordered from highlevel to lowlevel (technical) as much as possible

Core principle

XR Macros use querystrings, but are HTML-agnostic (though pseudo-XR Fragment browsers can be implemented on top of HTML/Javascript).
An XR Macro is 3D metadata which starts with '!' (!clickme: fog=0,10 e.g.)
Metadata-values can contain the | symbol to 🎲 roundrobin variable values (!toggleme: fog=0,10|fog=0,1000 e.g.)
XR Macros acts as simple eventhandlers for URI Fragments: they are automatically published on the (XR Fragments) hashbus, to act as events (so more serious scripting languages can react to them as well).
XR Macros can assign object metadata (!setlocal: foo=1 writes foo:1 metadata to the object containing the !setlocal metadata)
XR Macros can assign global metadata (!setfoo: #foo=1 writes foo:1 metadata to the root scene-node)

These very simple principles allow for rich interactions and dynamic querying

Conventions and Definitions

See appendix below in case certain terms are not clear.

List of XR Macros

(XR) Macros can be embedded in 3D assets/scenes.
Macros enrich existing spatial content with a lowcode, limited logic-layer, by recursive (economic) use of the querystring syntax (which search engines and XR Fragments already uses.
This is done by allowing string/integer variables, and the | symbol to roundrobin variable values.
Macros also act as events, so more serious scripting languages can react to them as well.

key	type	example (JSON)	function	existing compatibility
`@bg`	string	`"@bg":"#cube"`	bg: binds fog near/far based to cube x/y/z (anim) values	custom property in 3D fileformats
`@fog`	string	`"@fog":"#cube"`	fog: binds fog near/far based to cube x/y (anim) values	custom property in 3D fileformats
`@scroll`	string	`"@scroll":"#cube"`	texturescrolling: binds texture x/y/rot based to cube x/y/z (anim) values	custom property in 3D fileformats
`@emissive`	string	`"@emissive":"#cube"`	day/night/mood: binds material's emissive value to cube x/y/z (anim) values	custom property in 3D fileformats

Usecase: click object

custom property	value	trigger when
!clickme	bg=1,1,1&foo=2	object clicked

Usecase: conditional click object

custom property	value	trigger when
#	foo=1	scene
!clickme	q=foo>2&bg=1,1,1	object clicked and foo > 2

when a user clicks an object with the custom properties above, it should set the backgroundcolor to 1,1,1 when foo is greater than 2 (see previous example)

Usecase: click object (roundrobin)

custom property	value	trigger when
!cycleme	day\|noon\|night	object clicked
day	bg=1,1,1	roundrobin
noon	bg=0.5,0.5,0.5	roundrobin
night	bg=0,0,0&foo=2	roundrobin

when a user clicks an object with the custom properties above, it should trigger either day noon or night in roundrobin fashion.

Usecase: click object or URI fragment, and scene load trigger

custom property	value	trigger when
#	random	scene loaded
#random	random	URL contains #random
!random	day\|noon\|night	#random, # or click
day	bg=1,1,1	roundrobin
noon	bg=0.5,0.5,0.5	roundrobin
night	bg=0,0,0&foo=2	roundrobin

custom property	value	trigger when
!random	!day	!noon
!day	bg=1,1,1	clicked in contextmenu
!noon	bg=0.5,0.5,0.5	clicked in contextmenu
!night	bg=0,0,0&foo=2	clicked in contextmenu

When interacting with an object with more than one !-macro, the XR Browser should offer a contextmenu to execute a macro.

In a similar way, when any !-macro is present on the sceneroot, the XR Browser should offer a context-menu to execute those macro's.

Event Bubble-flow

click object with (!clickme:AR or !clickme: !reset e.g.)

  ◻
  │  
  └── does current object contain this property-key (`AR` or `!reset` e.g.)?
         └── no: is there any (root)object containing property `AR`
           └── yes: evaluate its (roundrobin) XR macro-value(s) (and exit)
           └── no: trigger URL: #AR

click object with (!clickme:#AR|#VR e.g.)

  ◻
  │  
  └── apply the roundrobin (rotate the options, value `#AR` becomes `#VR` upon next click)
      └── is there any object with property-key (`#AR` e.g.)?
         └── no: just update the URL to `#AR`
           └── yes: apply its value to the scene, and update the URL to `#AR`

click object with (`!clickme`:`!foo|!bar|!flop` e.g.)

◻ │
└── apply the roundrobin (rotate the options, value !foo becomes !bar upon next click) └── is there any object with property-key (!foo e.g.)? └── no: do nothing └── yes: apply its value to the scene


> Note that only macro's can trigger roundrobin values or contextmenu's, as well as roundrobin values never ending up in the toplevel URL.

# Security Considerations


# IANA Considerations

This document has no IANA actions.

# Acknowledgments

* [NLNET](https://nlnet.nl)
* [Future of Text](https://futureoftext.org)
* [visual-meta.info](https://visual-meta.info)

# Appendix: Definitions 

|definition            | explanation                                                                                                                   |
|----------------------|-------------------------------------------------------------------------------------------------------------------------------|
|scene                 | a (local/remote) 3D scene or 3D file (index.gltf e.g.)                                                                        |
|3D object             | an object inside a scene characterized by vertex-, face- and customproperty data.                                             |
|XR fragments          | URI Fragment with spatial hints like `#pos=0,0,0&t=1,100` e.g.                                                                |
|query                 | an URI Fragment-operator which queries object(s) from a scene like `#q=cube`                                                  |
|FPS                   | frames per second in spatial experiences (games,VR,AR e.g.), should be as high as possible                                    |
|`◻`                   | ascii representation of an 3D object/mesh                                                                                     |
|(un)obtrusive         | obtrusive: wrapping human text/thought in XML/HTML/JSON obfuscates human text into a salad of machine-symbols and words       |

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