Slot it Like It's Hot:
Progress on the New
Animation System

"Progress report of the Animation & Rigging module, and presentation of plans for the coming year."

Blender's animation system has roots that go back a long time. The Action datablock, the NLA editor, the way animation data is stored and evaluated — these are systems that accumulated complexity over many Blender versions, each release adding capabilities on top of an architecture that was never designed for what it eventually became. The result has been a system that works well for straightforward cases and creates real friction in more complex ones: multiple animated objects sharing data, non-destructive animation layering, game-ready export workflows.

The new slot-based animation system is an attempt to address these limitations at the architectural level rather than patching around them. This talk at Blender Conference 2025 is the public progress report: where the development stands, what has shipped, what is still in progress, and what the module plans to tackle in the year ahead. For anyone who works with animation in Blender — whether character animation, motion graphics, procedural animation, or rigging — this presentation is the clearest available summary of where things are going.

What the Talk Covers

• What the slot system is and why it matters The central change in the new animation architecture is the introduction of slots — a layer of indirection between an Action datablock and the objects it animates. Rather than an Action being directly bound to a single object, it can contain animation data for multiple slots, each of which can be assigned to a different object. This sounds like a technical detail but has significant practical implications: it enables cleaner sharing of animation data across objects, more predictable NLA behaviour, and better support for complex rigging setups.
• Progress shipped in 2025 The talk reviews what has landed in Blender releases during the year — specific features, API changes, and workflow improvements that came out of the Animation & Rigging module's work. This section is useful as a concrete record of what changed and when, particularly for anyone maintaining scripts or add-ons that interact with animation data.
• Compatibility and migration Changing animation data architecture in a tool with millions of users and years of existing files is not straightforward. The talk addresses how the module is handling backward compatibility: what opens cleanly in new Blender versions, what requires migration, and where the transition period creates temporary inconsistencies that users should be aware of.
• NLA editor improvements The Non-Linear Animation editor has historically been one of Blender's most powerful and least approachable tools. The new architecture provides a foundation for making it more predictable. The talk covers specific improvements to how NLA strips interact with the slot system and what workflow scenarios this unlocks.
• Driver and constraint system updates Drivers and constraints sit adjacent to the core animation system and interact with it constantly. The progress report covers updates in this area — both improvements to existing behaviour and new capabilities that became possible with the architectural changes.
• Plans for the coming year The second half of the talk shifts from progress report to roadmap. Stüvel presents what the Animation & Rigging module has prioritised for the next development cycle — which problems are next in line, what the open questions are, and where community feedback has shaped the direction. This is one of the more transparent roadmap presentations in Blender's development culture.

Why Architecture Talks Matter for Artists

Developer progress reports can seem distant from the daily concerns of artists — too technical, too focused on internal plumbing. This one is worth watching for a different reason: the problems the slot system is solving are problems that experienced Blender animators and riggers encounter regularly. Unexpected NLA behaviour, the difficulty of sharing animation data cleanly between objects, the friction of complex constraint setups — these are workflow frustrations that have a root cause, and this talk explains both the cause and the fix.

Understanding the direction of a tool's development also changes how you invest your learning time. Techniques that work around current architectural limitations are worth knowing now but may be superseded soon. Techniques that align with where the system is going will compound in value. Stüvel's annual presentations are the best available guide to which is which in Blender's animation toolset.

About the Speaker

Dr. Sybren A. Stüvel is a Blender Foundation developer and the lead of the Animation & Rigging module. He has worked on Blender's animation systems for many years, with contributions ranging from the Alembic exporter to the core animation data architecture. His BCON presentations are notable for being genuinely informative rather than promotional — he discusses limitations and open problems with the same directness as achievements. Outside Blender, his background is in computer science research.

About Blender Conference 2025

Blender Conference is the annual gathering of the Blender community, held in Amsterdam. All sessions are recorded and released under Creative Commons licensing through the Blender Foundation's PeerTube instance at video.blender.org. More information about BCON25 at conference.blender.org/2025.

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