Upcoming Blender 5.0 Release & Compatibility Breakages

Announcements
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Blender 5.0 is expected in less than one year now. According to our Compatibility Policy, this is the next opportunity to make changes in Blender that introduce severe forward compatibility breakages. Blender 4.5 will have to be compatible with these changes, and allow some level of conversion between blendfiles from 5.x releases and older Blenders.

There are two main categories of changes that should only happen when switching to a new major version.

  • Blendfile Data: Changes to the blendfile format itself, or some of the stored data (e.g. heavy modifications to an existing ID type), that will make new blendfiles impossible to open in older releases.
  • Non-essential API changes: Changes to the Blender Python API that can be delayed, but need to be done at some point. For example, cleanups (renaming or removal of deprecated items), or refactors leading to modifications of existing behaviors.

General Schedule

All modules that have plans to introduce such forward incompatibilities should start working on it now. The goal is to have finalized plans and designs agreed on by the end of 2024, and to start implementing them in the first quarter of 2025.

As the owner of the Blendfile I/O, RNA and DNA areas of Blender, the Core module will coordinate the process and validate the designs regarding their compatibility handling.

Third Quarter 2024 - Planning & Design

Module teams discuss their plans for the module, and create TODO and/or Design tasks. All tasks must be listed in one of these two parent TODO tasks:

These two tasks will be used a reference and ground truth for coordination purposes.

It’s the responsibility of each module to reach out and ask for feedback from other affected/related modules during the design phase. They should ensure that all aspects of the proposed changes are well understood and accepted.

Modules should also update the main releases compatibility page with any planned significant user-level change as soon as possible.

First Semester 2025 - Implementation

Implementation work should start early in 2025. Especially regarding Blendfile breakages, all work must be done and merged before June 2025 (as Blender 4.5 will enter Beta on 04/06/2025).

Note that Blendfile breakage will likely require two working branches, one to implement forward compatibility changes in 4.5, and the other for the actual breaking changes in 5.0. Having these two branches in parallel will also make it easier to test blendfiles compatibility during development.

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Please don’t have an allegiance to deadlines here and only release when it can be guaranteed that the .blend file format of all things is not full of regressions causing mass-scale losses of data.

I ask that because the pattern I have been seeing with the accelerated rate of breaking changes is Blenderartists and other community sites swamped with massive complaint threads with claims of Blender going in a bad direction and the like. Things get better after 3 to 6 months, only for another release made on a deadline (regardless of stability and bugginess) to come out and start the process all over again. One consequence of this is the community being divided into smaller and smaller groups as fewer and fewer people make an immediate move to the latest.

Is not the slogan of the BF be to Put the fun back into 3D? If people have to fight the software every other release, then nothing is fun anymore.

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Yes, it’s a problem to keep in mind, but it sounds more like a subjective truth to me. I’d consider an up to date 3D program that is able to develop and evolve more rapidly to be more fun than asset compatibility.
So far even if breaking changes were introduced, upwards compatibility was still maintained by the devs as far as possible and I don’t expect that to change. But if it makes sense for something that needs to be done then so be it. I’d rather have a modern, performant and fun to use 3D program than compatibility at all costs.

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