Issue link: http://digital.copcomm.com/i/1144162
s u m m e r 2 0 1 9 c g w 5 1 I magine the frustration of being under a tight deadline on a big project and not being able to communicate with those you are working with. The same situation can occur when digital artists from different studios or even groups within the same facil- ity try to share shots or assets on a project. Alembic helps facilitate that communication for a smoother workflow. Alembic is an open computer graphics interchange framework that distills complex, animated scenes into a non-procedural, application-independent set of baked geo- metric results. This distillation of scenes into baked geometry is exactly analogous to the distillation of lighting and rendering scenes into rendered image data. Alembic started as a collaboration between Sony Pictures Imageworks and Industrial Light & Magic in 2009. At the time, Imageworks had just finished a refresh of its internal baked file format, but the industry was rapidly beginning to change. More than one studio was now working on a single project, so there was more of a need to share data. At the same time, ILM was just starting to update its internal geometry file format. The two companies decided to collaborate and release their code as open source in the hopes of increasing industry adoption. Baked geometry means that the final point positions, transforms, normals, and so forth are stored to the file directly per sample. However, the recipe that helps contribute to the final calculations is most oen not stored. The baked requirement is important for a few reasons. The amount of time it takes to calculate the final asset is usually time prohibitive. Custom proprietary tools that a company does not want to share could also be part of what goes into calculating these final positions. The same func- tionality to create the asset is oen not available in all content creation packages. Although the amount of disk space used can sometimes be greater in baked form, this form is much easier to deal with throughout modern VFX pipelines and between vendors. Most baked geometry formats at the time were either too simple to represent the modern needs of computer graphics appli- cations, inefficient for the vast amounts of geometry that were being created, or totally proprietary so that it was only supported in a handful of digital content creation pack- ages. The collaboration allowed Imageworks and ILM to do a ground up rethink of what was needed and what could be improved, and to gather feedback from the open- source community. OVERCOMING THE OBSTACLES One of the annoying constraints of many traditional baked file formats is that there is a file per asset per frame. This can become cumbersome when there are thousands of frames with exotic subframe sampling required for motion blur when rendering. That can lead to situations where you need to find all the files that are available but only read a small handful of them to get the sam- ples you want. Alembic allows you to store all of your samples in one file. (Although, the classical approach is still possible.) Different shapes can have different sampling rates, as well. This is oen used to oversample cheaper objects to calculate like transforms, and more sparsely sample expensive things like heavy meshes with many points. One of the most novel ideas in Alembic compared with other file formats is how it can automatically share data written to it without needing to be specified by the user. Oftentimes with an asset, the same data indeed will be the same across ALEMBIC TRANSFORMS THE WORKFLOW AMONG FACILITIES BY LUCAS MILLER SHARE SHARE ALIKE AND