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Introduction

Alembic is an open format for baked animated geometry, created by Sony Pictures Imageworks and Lucasfilm and released in 2011. It stores the result of an animation, not the rig or simulation that made it: the position of every point on every frame, together with the object hierarchy, transforms, cameras and curves.

This lets one studio department hand finished animation to another, for example from animation to lighting or effects, in a form any program can play back without the original setup. It is used widely in film, television and games.

Structure

An Alembic archive is a tree of objects, such as transforms, polygon meshes, subdivision surfaces, curves, points and cameras. Each object has properties, and each property holds one sample per time step. Samples that repeat are stored once, so a mesh whose topology does not change keeps one copy of its face lists.

The archive is written through a back end. Early files used HDF5 and start with the HDF5 signature. Since Alembic 1.5 the default is Ogawa, a simpler and faster layout of groups and data blocks, and these files start with the text Ogawa.

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