Currently the procedural will add an entry to the cache for every frame
even if the data only changes seldomly. This means that in some cases we
will have duplicate data accross frames.
The cached data is now stored separately from the time information, and
an index is used to retrieve it based on time. This decoupling allows
for multiple frames to point to the same data.
To check if two arrays are the same, we compute their keys using the
Alembic library's routines (which is based on murmur3), and tell the
cache to reuse the last data if the keys match.
This can drastically reduce memory usage at the cost of more processing
time, although processing time is only increased if the topology may
change.
Static initialization order was not guaranteed to be correct for node base
types. Now wrap all initialization in accessor functions to ensure the order
is correct.
Did not cause any known bug on Linux/macOS/Windows, but showed up on this
platform.
This type, CacheLookupResult, holds the data for the current time, or an
explanation as to why no data is available (already loaded, or simply
nothing available). This is useful to document the behavior of the code
but also, in future changes, to respond appropriately for missing data.
Inside of the procedural, instances are AlembicObjects which point to
the AlembicObject that they instance.
In Alembic, an instance is an untyped Object pointing to the original
(instanced) one through its source path. During the archive traversal we
detect such instances and, only if the instanced object is asked to be
rendered, set the instance's AlembicObject to point to the original's
AlembicObject.
Cycles Object Nodes are created for each AlembicObject, but only for
non-instances are Geometries created, which are then shared between
Object Nodes. It is supposed, and expected, that all instances share the
same shaders, which will be set to be the ones found on the original
object.
As for caching, the data cache for an AlembicObject is only valid for
non-instances and should not be read to or from as it is implicitly
shared.
This will help support instancing as cache building is now decoupled
from the logic to update the Nodes' sockets as data (and cache) will
need to be shared by different Geometries somehow, and also simplify
implementing different data caching methods by centralizing this
operation.
We need to explicitely tag the Attribute and AttributeSet as modified if
we change or add/remove data. This is more of a bandaid until attributes
handling is refactored to be able to reuse routines from the Attribute
API.
The missing update has two sources:
The TimeSampling used for looking up transformations in the cache was
uninitialized. To fix this, simply use the TimeSampling from the last
transformation in the hierarchy (that is the object's parent), which
should also contain the time information for all of its parents.
The objects are not tagged for update when their trasformations change.
The implementation is currently optimized to load animation sequences once
and then quickly scrubbing through them. Later on an option should be added
to optimize for memory usage and only load the current frame into memory.
Currently mesh and curve objects are supported, including support for UV and
vertex color attributes. Missing still is support for arbitrary attributes and
motion blur, as well as better handling of changing topology. Shader assignments
are made using FaceSets found in the Alembic archive.
The animation (and constant) data of the objects inside the Alembic archive is
loaded at once at the beginning of the render and kept inside a cache. At each
frame change we simply update the right socket of the corresponding Cycles node
if the data is animated. This allows for fast playback in the viewport
(depending on the scene size and compute power).
Note this is not yet exposed in the Blender UI, it's a feature that is still under
development and not ready for general use.
Ref T79174, D3089
