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

[cee jay]

Could this be done with custom properties?
This will need a custom python script to add a GUID property to every
object that doen't have one when depsgraph is updated for example. So now
maybe export a JSON (or any oyher format, really) containing GUID-Object
name pairs that the engine could read and use?
That way you won't need to modify the blender code at all, if that causes a
problem.

On Fri, Nov 13, 2020, 19:35 Juan Linietsky via Bf-committers <
bf-committers at blender.org> wrote:

> 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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