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<br>
<h1>XR Macros</h1>
<br>
<pre>
stream: IETF
area: Internet
status: informational
author: Leon van Kammen
date: 2023-04-12T00:00:00Z
workgroup: Internet Engineering Task Force
value: draft-XRMACROS-leonvankammen-00
</pre>
<h1class="special"id="abstract">Abstract</h1>
<p>This draft offers a specification for embedding macros in existing 3D scenes/assets, to offer simple interactions and configure the renderer further.<br>
Together with URI Fragments, it allows for rich immersive experiences without the need of a complicated sandboxed scripting languages.</p>
<blockquote>
<p>Almost every idea in this document is demonstrated at <ahref="https://xrfragment.org">https://xrfragment.org</a>, as this spec was created during the <ahref="https://xrfragment.org">XR Fragments</a> spec.</p>
</blockquote>
<sectiondata-matter="main">
<h1id="introduction">Introduction</h1>
<p>How can we add more features to existing text & 3D scenes, without introducing new dataformats?<br>
Historically, there’s many attempts to create the ultimate markuplanguage or 3D fileformat.<br>
Their lowest common denominator is: (co)authoring using plain text.<br>
Therefore, XR Macros allows us to enrich/connect existing dataformats, by offering a polyglot notation based on existing notations:<br></p>
<ol>
<li>getting/setting common used 3D properties using querystring- or JSON-notation</li>
<p>NOTE: The chapters in this document are ordered from highlevel to lowlevel (technical) as much as possible</p>
</blockquote>
<h1id="core-principle">Core principle</h1>
<ol>
<li>XR Macros use querystrings, but are HTML-agnostic (though pseudo-XR Fragment browsers <strong>can</strong> be implemented on top of HTML/Javascript).</li>
<li>An XR Macro is 3D metadata which starts with ‘!’ (<code>!clickme: fog=0,10</code> e.g.)</li>
<li>Metadata-values can contain the <code>|</code> symbol to 🎲 roundrobin variable values (<code>!toggleme: fog=0,10|fog=0,1000</code> e.g.)</li>
<li>XR Macros acts as simple eventhandlers for URI Fragments: they are automatically published on the (<ahref="https://xrfragment.org">XR Fragments</a>) hashbus, to act as events (so more serious scripting languages can react to them as well).</li>
<li>XR Macros can assign object metadata (<code>!setlocal: foo=1</code> writes <code>foo:1</code> metadata to the object containing the <code>!setlocal</code> metadata)</li>
<li>XR Macros can assign global metadata (<code>!setfoo: #foo=1</code> writes <code>foo:1</code> metadata to the root scene-node)</li>
<h1id="conventions-and-definitions">Conventions and Definitions</h1>
<p>See appendix below in case certain terms are not clear.</p>
<h1id="list-of-xr-macros">List of XR Macros</h1>
<p>(XR) Macros can be embedded in 3D assets/scenes.<br>
Macros enrich existing spatial content with a lowcode, limited logic-layer, by recursive (economic) use of the querystring syntax (which search engines and <ahref="https://xrfragment.org">XR Fragments</a> already uses.<br>
This is done by allowing string/integer variables, and the <code>|</code> symbol to roundrobin variable values.<br>
Macros also act as events, so more serious scripting languages can react to them as well.<br></p>
<p>when a user clicks an object with the custom properties above, it should set the backgroundcolor to <code>1,1,1</code> when <code>foo</code> is greater than <code>2</code> (see previous example)</p>
<p>when a user clicks an object with the custom properties above, it should trigger either <code>day</code><code>noon</code> or <code>night</code> in roundrobin fashion.</p>
<p>When interacting with an object with more than one <code>!</code>-macro, the XR Browser should offer a contextmenu to execute a macro.</p>
</blockquote>
<p>In a similar way, when <strong>any</strong><code>!</code>-macro is present on the sceneroot, the XR Browser should offer a context-menu to execute those macro’s.</p>
<h2id="event-bubble-flow">Event Bubble-flow</h2>
<p>click object with (<code>!clickme</code>:<code>AR</code> or <code>!clickme</code>: <code>!reset</code> e.g.)</p>
<pre><code> ◻
│
└── 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
</code></pre>
<p>click object with (<code>!clickme</code>:<code>#AR|#VR</code> e.g.)</p>
<pre><code> ◻
│
└── 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.)
</code></pre>
<p>◻
│<br>
└── apply the roundrobin (rotate the options, value <code>!foo</code> becomes <code>!bar</code> upon next click)
└── is there any object with property-key (<code>!foo</code> e.g.)?
└── no: do nothing
└── yes: apply its value to the scene
“`</p>
<blockquote>
<p>Note that only macro’s can trigger roundrobin values or contextmenu’s, as well as roundrobin values never ending up in the toplevel URL.</p>
