User guide

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By default Katana understands proxies created using Alembic, which are simply declared using the path to the
relevant .abc file. You can also customize Katana to read proxies from custom data formats by creating a Scene
Graph Generator to read the relevant file format and using a plug-in for the Viewer that simply declares which Scene
Graph Generator to use for a given file extension.
Proxies can also be animated if required. If the proxy file has animation that will be used by default, but you can also
explicitly control what frame from a proxy is read using these additional attributes:
proxies.currentFrame proxies.firstFrame proxies.lastFrame
To help users navigate the scene graph, group locations can be indicated as being 'assemblies' or 'components'. The
origins of these terms are from Sony Pictures Imageworks where they are used to indicate whether an asset is a
building block component or an assembly of other assets, but Katana's user interface they are simply used as
indicators for locations that would be good for the user to open the scene graph up to. In the Scene Graph viewer
there are options to open to the next Assembly, Component of LOD level, and double clicking on a location
automatically opens the scene graph up to the next of these levels.
For the user it's useful if proxies or bounding boxes are at groups indicated as being 'assemblies' or 'components', so
the user can open the scene graph to those levels and see a sensible representation of the assets in the Viewer.
To turn a group location into an 'assembly' or 'component' the 'type' attribute at that location simply needs to be set
to 'assembly' or 'component'. If you are using ScenegraphXML (see section 5.4) there is support for indicating
locations as being 'assemblies' or 'components' within the ScenegraphXML file.
In general it also help users if the hierarchy isn't too 'flat', with groups with very large number of children. Structure
can help users navigate the Scene Graph.
Level of Detail Groups
Levels of Detail (LODs) are used to allow an asset to have multiple representations. Katana can then be used to select
which representation is used in a given render output.
Conventionally LODs are used to hold a number of asset versions with different amount of geometric complexity,
such as a high level of detail to use if the asset is close to the camera and middle and low levels of detail if the asset is
further away. By selecting an appropriate version of each asset to send to the renderer the overall complexity of a
shot can be controlled and render times managed.
In Katana LODs can also be used to declare completely different versions of an asset for different target outputs,
such as a bounding volume representation for a volumetric renderer in addition to standard geometrical
representations such as polygon meshes to be used by conventional scanline renderers or ray-tracers.
Multiple levels of detail for an asset are declared by having a 'Level of Detail Group' location which has a number of
'Level of Detail' child locations. Each of these child locations has metadata to determine when that level of detail is to
10 STRUCTURED SCENE GRAPH DATA | LEVEL OF DETAIL GROUPS