Update model

Author: JulieWinchester

source/presentation/4.0/model.md

@@ -304,7 +304,7 @@ All Containers _MUST_ be identified by a URI and it _MUST_ be an HTTP(S) URI. Th
 
 Containers _SHOULD_ have an `items` property which is a list of Annotation Pages. Each Annotation Page, defined below, maintains a list of Annotations, which associate Content Resources to be rendered as part of the Container. Annotations that do not associate content to be rendered, but instead are about the Container itself, such as a comment or tag, are recorded using Annotation Pages in the `annotations` property of the Container. A Container _MAY_ have zero annotations associated with it and still be useful, such as when the properties of the Container convey to the user that it represents a page that has not been digitized, or there is otherwise no digital content available to display. In this case the `items` property is not included.
 
-Containers specify extents in space and/or time with one or more space or time dimensions such as `height`, `width`, or `duration`. These dimensions allow resources to be associated with specific regions of the Canvas, within the space and/or time extents provided. Content _MUST NOT_ be associated with space or time outside of the Container's dimensions, such as at coordinates below 0,0 or greater than specified height or width for a Canvas, or before 0 seconds or after the duration for a Timeline. Content resources that have dimensions which are not defined for the Container _MUST NOT_ be associated with that Container by an Annotation that has the `motivation` value "painting". For example, it is valid to use an Annotation that has the `motivation` value "painting" to associate an Image (which has only height and width) with a Canvas that has `height`, `width`, and `duration` properties, but it is an error to associate a Video resource (which has height, width and duration) with a Canvas that does not `duration`. Such a resource _SHOULD_ instead be referenced using the rendering property, or by Annotations that have a `motivation` value other than "painting" in the annotations property.
+Containers specify extents in space and/or time with one or more space or time dimensions such as `height`, `width`, or `duration`. These dimensions allow resources to be associated with specific regions of the Canvas, within the space and/or time extents provided. Content _MUST NOT_ be associated with space or time outside of the Container's dimensions, such as at coordinates below 0,0 or greater than specified height or width for a Canvas, or before 0 seconds or after the duration for a Timeline. Content resources that have dimensions which are not defined for the Container _MUST NOT_ be associated with that Container by an Annotation that has the `motivation` value "painting". For example, it is valid to use an Annotation that has the `motivation` value "painting" to associate an Image (which has only height and width) with a Canvas that has `height`, `width`, and `duration` properties, but it is an error to associate a Video resource (which has height, width and duration) with a Canvas that does not `duration`. Such a resource _MAY_ instead be referenced using the rendering property, or by Annotations that have a `motivation` value other than "painting" in the annotations property.
 
 __Properties__<br/>
 All Containers _MUST_ have the following properties: [id](#id), and [type](#type)<br/><br/>
@@ -348,7 +348,7 @@ A Scene is a Container that represents an infinitely large three-dimensional spa
 
 The axes of the coordinate system are measured in arbitrary units. All axes use the same unit scaling and do not necessarily correspond to any physical unit of measurement, unless `spatialScale` is supplied.
 
-All resources that can be added to a Scene have an implicit (e.g. Lights, Cameras) or explicit (e.g. Models, Scenes), local coordinate space. Transforms may modify the local coordinate space of a resource relative to the Scene’s "global" space.
+All 3d resources that can be added to a Scene have an implicit (e.g. Lights, Cameras) or explicit (e.g. Models, Scenes) local coordinate space. Transforms may modify the local coordinate space of a resource relative to the Scene’s "global" space.
 
 __Properties__<br/>
 A Scene _MAY_ have the following additional properties: [duration](#duration).
@@ -373,7 +373,7 @@ When Annotations are used to associate content resources with a Canvas, the cont
 
 Annotations in IIIF _SHOULD NOT_ use the `bodyValue` property defined by the Web Annotation Data Model, but instead use the more consistent TextualBody class.
 
-For Timelines and Canvases, Annotations _MUST NOT_ target spatial or temporal points or regions outside of the bounds of the Container. For Scenes with a `duration`, Annotations _MUST NOT_ target temporal points or regions outside of that duration. Scenes, Canvases and other content with spatial extents _MUST NOT_ be annotated directly onto a Timeline which does not have a spatial extent. Resources with a `duration`, including Timelines and Canvases, _MAY_ be painted into Canvases and Scenes without a `duration`, however the playback of the resource will not able to be controlled or synchronized with the playback of other time-based media.
+For Timelines and Canvases, Annotations _MUST NOT_ target spatial or temporal points or regions outside of the bounds of the Container. For Scenes with a `duration`, Annotations _MUST NOT_ target temporal points or regions outside of that duration. Scenes, Canvases and other content with spatial extents _MUST NOT_ be annotated directly onto a Timeline which does not have a spatial extent. Resources with a `duration`, including Timelines and Canvases, _MUST NOT_ be painted into Canvases and Scenes without a `duration`, however they _MAY_ instead be referenced by a non-painting Annotation or using the rendering property.
 
 __Properties__<br/>
 An Annotation _MUST_ have the following properties: [id](#id), [type](#type), [target](#target), [motivation](#motivation).<br/><br/>
@@ -470,12 +470,18 @@ Content Resources _MUST_ have an HTTP(s) given in `id`. It _MUST_ be able to be
 
 If the Content Resource is an Image, and a IIIF Image service is available for it, then the `id` property of the Content Resource _MAY_ be a complete URI to any particular representation supported by the Image Service, such as `https://example.org/image1/full/1000,/0/default.jpg`, but _MUST NOT_ be just the URI of the Image Service. The Image _SHOULD_ have the service referenced from it using the `service` property.
 
-If the Content Resource is a 3d Model, then regardless of the file format, it is treated as being within an infinitely large three dimensional space with an origin (0 on all three axes). This is described as its "local coordinate space".
+If the Content Resource is a 3d Model, then regardless of the file format, it is treated as being within an infinitely large three dimensional space with an origin (0 on all three axes). This is described as its "local coordinate space". 3d Content Resources _MAY_ be painted into Scenes via a painting Annotation. When painted as an Annotation, the origin of the 3d Content Resource's local coordinate space _MUST_ be aligned with either the Scene coordinate origin by default or with a specific 3d point in the Scene if a [Point Selector](#point-selector) is used.
+
+Non-3d Content Resources such as images, audio, and video _MUST NOT_ be painted into a Scene as Annotations. Instead, to include image and video resources in a Scene, the resource(s) _MUST_ be painted on to a Canvas that is painted into the Scene. To include audio resources in a Scene, the resource(s) or Timeline _MUST_ be referenced by an AudioEmitter that is painted into the Scene.
 
 If there is a need to distinguish between Content Resources, then all such resources _SHOULD_ have the `label` property.
 
 Containers _MAY_ be treated as content resources for the purposes of annotating on to other Containers. In this situation, the Container _MAY_ be [embedded][prezi30-terminology] within the Annotation, be a reference within the same Manifest, or require dereferencing to obtain its description. This is often described as "nesting".
 
+A Canvas painted into a Scene has special requirements. The top-left corner of the Canvas _MUST_ be aligned with either the Scene coordinate origin by default or with a specific 3d point in the Scene if a [Point Selector](#point-selector) is used. The Canvas _MUST_ be scaled to the Scene such that Canvas coordinate dimensions after any [Transforms](#transforms) are applied correspond to Scene coordinate dimensions with 1:1 scaling. A Canvas painted into a Scene as an Annotation has forward and backward faces, and by default the forward face is toward the positive z axis of the Scene, though this may be modified by Transforms. The content of the Canvas _SHOULD_ be displayed on the forward face, and the backward face _SHOULD_ display either any `backgroundColor` of the Canvas or a reverse view of the content.
+
+A Scene painted into a Scene has one special requirement, that any `backgroundColor` of the Scene to be painted _SHOULD_ be ignored.
+
 __Properties__<br/>
 A Content Resource _MUST_ have the following properties: [id](#id), and [type](#type)<br/><br/>
 A Content Resource _SHOULD_ have the following properties: [label](#label)<br/><br/>
@@ -527,6 +533,8 @@ There are common use cases in which a point, rather than a range or area, is the
 
 The spatial aspect of the point is given with `x` and `y` for a two-dimensional point, along with `z` for a three-dimentional point. The temporal aspect of the point is given with `instant`. If `instant` is not supplied, and the target resource has a `duration`, the selector is interpreted as targeting the entire duration. If `instant` is supplied, but no spatial point, the selector is interpreted as targeting the entire spatial aspect of the resource.
 
+For 3d content resources painted into a Scene that have a local coordinate space relative to the relatively global coordinate space of the Scene, clients _MUST_ align the local coordinate origin of the content resource with the 3d point indicated by the Point Selector within the Scene. Thus the 3d resource's origin is placed at the desired point in the Scene. For a Canvas painted into a Scene as an Annotation, the top-left corner of the Canvas (the Canvas coordinate origin) _MUST_ be aligned with the 3d point indicated by the Point Selector within the Scene.
+
 __Properties__<br/>
 A Point Selector _MUST_ have the following properties: [type](#type)<br/><br/>
 A Point Selector _MAY_ have the following properties: [id](#id), [x](#x), [y](#y), [z](#z), and [instant](#instant).