User guide

11 Look Files
Katana's Look Files are a powerful general purpose tool that can be used in a number of ways. In essence they
contain a baked cache of changes that can be applied to a section of scene graph to take it from an initial state to a
new one.
Typically there are used to store all the relevant changes that need to be applied to take an asset from its raw state,
as delivered from modeling with no materials, to a look developed state ready for rendering. They can also be used
for other purposes such as to contain palettes of materials or to hold show standard settings for render outputs
such as image resolutions, anti-aliasing settings and what output channels (AOVs) to use.
Different studios define the tasks done by look development and lighting in different ways. In this section we're
going to look at what could be considered a typical example of the tasks to give a clear example of possible use, but
the actual work done by different departments could bedifferent. Look files should be seen as a useful flexible
general tool that can be used to pass baked caches of scene graph modifications from one Katana project to
another.
Handing Off Looks
The most standard use of Katana's Look Files is to describe what materials are needed for a given asset, such as a
character, car or building, and which material is assigned to each geometry location. The look file can also record any
overrides such as modifications to shaders on particular locations, for example if a given object needs the specular
intensity on a shader setting to a special value. The Look File can also record the shaders and assignments that are
needed for a number of different passes, such as if you are going to do separate renders for the beauty pass,
ambient occlusion, volumetric renderer etc...
The traditional workflow is that Look Development will define how each asset should look in all the different render
passes required. They then 'bake' out a Look File for each asset, or multiple look files if there are a number of
alternative look variants for an asset.
The LookFile records this data in a form that can be re-applied to the 'naked' asset in Lighting. In Lighting the
appropriate Look File is assigned to each asset. Downstream in the Katana graph when you want to split into all the
different separate passes you do a 'LookFileResolve' which actually does the work of re-applying all the materials and
other changes to the asset that are needed for a given pass.