[Bf-committers] Proposing a unique ID for Blender objects system, for use with game engines.

[Juan Linietsky]

Yes, as mentioned, the IDs need to be unique and generated at the time of
the object creation (for objects in 3D space, meshes , materials, etc) as
well as persisting between saving and load. They should not change when a
node is renamed.

With this, we can export most likely via GLTF/FBX extension and we can
easily tell when a node, material, object, mesh, etc. was renamed, so we
don't lose any modifications made to this on the engine side.

Juan


On Thu, Nov 12, 2020 at 10:51 PM Scott Wilson via Bf-committers <
bf-committers at blender.org> wrote:

> That's only valid for the lifetime of the object, though (it uses the
> memory location of the object). If you restart Blender, delete the Python
> object, or create a new Python object that points to the same memory in C,
> then all the IDs will likely be different for the same object in C. Also,
> the C objects' memory locations will likely change between Blender
> restarts, and deletions.
>
> On Thu., Nov. 12, 2020, 5:20 p.m. AMDBCG via Bf-committers, <
> bf-committers at blender.org> wrote:
>
> > Python has an id for each object that can be referenced in your Blender
> > importer
> >
> > https://www.programiz.com/python-programming/methods/built-in/id - where
> > id is the main id of the object
> >
> > -Robert Fornof (amdbcg)
> >
> > On 11/12/2020 9:24 AM, Juan Linietsky via Bf-committers wrote:
> > > Hi guys, lead Godot dev here.
> > >
> > > I wanted to discuss with you a problem we are often having that I am
> not
> > > certain how it can be solved entirely from our side, I add a proposal
> for
> > > this, but if you guys have a better recommendation, I'm very open to
> any
> > > ideas.
> > >
> > > Basically, Godot will import scenes (GLTF/FBX/DAE/etc) as they come
> from
> > > blender, and it generates the same object names, resource names, etc.
> as
> > > they come from Blender and the resource file.
> > >
> > > We use the same names so we can keep track of changes in the Blend
> file.
> > If
> > > an object is moved, a material is changed, etc. we detect on re-import
> > and
> > > everything is updated in Godot.
> > >
> > > This is especially more annoying in Godot than in other game engines,
> > > because Godot can read the whole Blender scene and keep it more or less
> > > intact, so users love using this for level design workflow (so they can
> > > design levels in Blender).
> > >
> > > So, the problem is that it often happens that for some reason, artists
> > want
> > > to rename the objects in Blender. Be it because they didn't care at the
> > > beginning and they want to become more organized later, or because the
> > > scene became bigger and they need to make their naming of things more
> > > precise to navigate it around. In this situation, when something is
> > renamed
> > > on the Blender side and re-exported, the game engines have no idea
> where
> > > this object went, so we need to either remove it (resulting in loss
> data)
> > > it or orphan it (resulting in duplicated data).
> > >
> > > While I do think that good practices solve this and this is probably
> not
> > > such an issue in a professional environment, truth is that game
> > development
> > > has become a huge hobbyist activity, and our users find this situation
> > > constantly and are annoyed with it, and there is nothing we can do from
> > our
> > > side.
> > >
> > > The obvious proposal to solve this would be to ask Blender whether it's
> > > possible to generate a unique object ID (UUID?) and make sure it does
> not
> > > change over time even if objects are renamed, then changing the
> > exporters a
> > > bit to (optionally if selected in the export settings) add this
> > information
> > > as extensions in the existing format (on GLTF it should be rather
> easy).
> > >
> > > If you guys think this is possible, it would be very helpful for us, if
> > you
> > > have other ideas on how we could solve this, we are very open to
> > discussion.
> > >
> > > Best
> > >
> > > Juan
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