Support geometry node in glTF exporter #94953

New Issue

Julien Duroure · 2022-01-16T14:45:45+01:00

Julien Duroure commented

2022-01-16 14:45:45 +01:00

This should be possible when API will manage it.
Current code used by glTF exporter:

depsgraph = bpy.context.evaluated_depsgraph_get()
blender_mesh_owner = blender_object.evaluated_get(depsgraph)
blender_mesh = blender_mesh_owner.to_mesh(preserve_all_data_layers=True, depsgraph=depsgraph)

This should be possible when API will manage it. Current code used by glTF exporter: ``` depsgraph = bpy.context.evaluated_depsgraph_get() blender_mesh_owner = blender_object.evaluated_get(depsgraph) blender_mesh = blender_mesh_owner.to_mesh(preserve_all_data_layers=True, depsgraph=depsgraph) ```

Julien Duroure commented

2022-01-16 14:45:45 +01:00

Added subscribers: @JulienDuroure, @lictex_1, @GeorgiaPacific, @JacquesLucke

Jacques Lucke commented

2022-01-18 12:31:02 +01:00

I'm not entirely sure what part of geometry nodes you want to support exactly with this task.
There are two main things:

Generic attributes. This probably just requires a few more lines in the exporter to export these additional data layers.
Instances. I don't know the glTF format very well. Does it support some kind of instancing or can a file only contain one mesh? Either way, we could potentially add a realize_instances option to the to_mesh function.

I'm not entirely sure what part of geometry nodes you want to support exactly with this task. There are two main things: * Generic attributes. This probably just requires a few more lines in the exporter to export these additional data layers. * Instances. I don't know the glTF format very well. Does it support some kind of instancing or can a file only contain one mesh? Either way, we could potentially add a `realize_instances` option to the `to_mesh` function.

Julien Duroure commented

2022-01-18 12:43:37 +01:00

Hello Jacques,

My main issue was about retrieving geometry itself in python, because API doesn't return any data if node tree does not have a Realize Instances Node.
Adding an option to to_mesh could be a great solution for any dev that want retrieve geometry with the python API

(Instances are already managed in glTF exporter)

Hello Jacques, My main issue was about retrieving geometry itself in python, because API doesn't return any data if node tree does not have a Realize Instances Node. Adding an option to to_mesh could be a great solution for any dev that want retrieve geometry with the python API (Instances are already managed in glTF exporter)

Jacques Lucke commented

2022-01-18 13:05:40 +01:00

Instances are already managed in glTF exporter

Can you give some more details to how instances are handled? I couldn't find related code in the exporter when I quickly skimmed over it. A Realize Instances node is only necessary when the tree actually outputs instances. If the file format exports instances, then those should be exported as instances as well probably, instead of being merged into a single mesh.

> Instances are already managed in glTF exporter Can you give some more details to how instances are handled? I couldn't find related code in the exporter when I quickly skimmed over it. A `Realize Instances` node is only necessary when the tree actually outputs instances. If the file format exports instances, then those should be exported as instances as well probably, instead of being merged into a single mesh.

Julien Duroure commented

2022-01-18 13:12:34 +01:00

Sorry, I probably misunderstand / use a wrong world. What is currently supported is different object sharing same mesh data.

My request here is more about be able to get mesh data using bpy when there is Geometry Node modifier, and no Realize Instances node in node tree. Seems this is currently not possible (or I didn't find how). (Whatever we want a merge into single mesh or not)

Sorry, I probably misunderstand / use a wrong world. What is currently supported is different object sharing same mesh data. My request here is more about be able to get mesh data using bpy when there is Geometry Node modifier, and no ```Realize Instances``` node in node tree. Seems this is currently not possible (or I didn't find how). (Whatever we want a merge into single mesh or not)

Jacques Lucke commented

2022-01-18 13:16:32 +01:00

Ah I see, so e.g. dupli objects are not yet exported to glTF either, right?

There is an api that should give you the data you are looking for: https://wiki.blender.org/wiki/Reference/Release_Notes/3.0/Python_API#Geometry_Instancing
It may not fit neatly into the current architecture of the exporter, not sure. Maybe you can wrap it to make it fit better.
I hope we can get a better / more direct API in the future, but not sure if we can get it in 3.1.

Ah I see, so e.g. dupli objects are not yet exported to glTF either, right? There is an api that should give you the data you are looking for: https://wiki.blender.org/wiki/Reference/Release_Notes/3.0/Python_API#Geometry_Instancing It may not fit neatly into the current architecture of the exporter, not sure. Maybe you can wrap it to make it fit better. I hope we can get a better / more direct API in the future, but not sure if we can get it in 3.1.

Julien Duroure commented

2022-01-18 13:26:10 +01:00

Ah I see, so e.g. dupli objects are not yet exported to glTF either, right?

You are right. They are managed in this branch for now: https://github.com/KhronosGroup/glTF-Blender-IO/pull/1378

I will have a look on api you pointed it out. Thanks!

> Ah I see, so e.g. dupli objects are not yet exported to glTF either, right? You are right. They are managed in this branch for now: https://github.com/KhronosGroup/glTF-Blender-IO/pull/1378 I will have a look on api you pointed it out. Thanks!

Jacques Lucke commented

2022-01-18 13:29:22 +01:00

I think you pasted the branch name incorrectly.

Julien Duroure commented

2022-01-18 13:31:35 +01:00

I think you pasted the branch name incorrectly.

Fixed, sorry

> I think you pasted the branch name incorrectly. Fixed, sorry

Hans Goudey commented

2022-11-05 17:02:24 +01:00

Added subscriber: @HooglyBoogly

Hans Goudey commented

2022-11-05 17:02:24 +01:00

I read some updates recently and I think this might be finished-- both attributes and geometry instances. Is that right?

Zhen Dai commented

2022-11-25 07:17:02 +01:00

Added subscriber: @Zhen-Dai

Zhen Dai commented

2022-11-25 07:21:43 +01:00

Same question as Hans but looks like it isn't merged yet: https://github.com/KhronosGroup/glTF-Blender-IO/pull/1786

To make the instancing workflow truly usable it probably need support for EXT_mesh_gpu_instancing also, such as this fork: https://github.com/takahirox/glTF-Blender-IO-EXT-mesh-gpu-instancing

Same question as Hans but looks like it isn't merged yet: https://github.com/KhronosGroup/glTF-Blender-IO/pull/1786 To make the instancing workflow truly usable it probably need support for `EXT_mesh_gpu_instancing` also, such as this fork: https://github.com/takahirox/glTF-Blender-IO-EXT-mesh-gpu-instancing

Julien Duroure commented

2022-11-25 08:24:22 +01:00

Hello,

Yes, the PR is not yet merged, and not finished yet. I will close this ticket when PR will be merged.
Implementing EXT_mesh_gpu_instancing is also on the roadmap of the PR.

Hello, Yes, the PR is not yet merged, and not finished yet. I will close this ticket when PR will be merged. Implementing EXT_mesh_gpu_instancing is also on the roadmap of the PR.

Bastien Montagne added this to the Pipeline, Assets & IO project 2023-02-09 15:40:38 +01:00

Lorenz-Wildberg commented

2024-01-04 02:23:16 +01:00

Hi,
since the last comment on this issue, the EXT_mesh_gpu_instancing gltf extension got ratified, and blender since 4.0 natively supports in the gltf exporter this extension. Only what's missing is this issues. Has there been any progress? Thanks in advance!

Hi, since the last comment on this issue, the `EXT_mesh_gpu_instancing` gltf extension got ratified, and blender since 4.0 natively supports in the gltf exporter this extension. Only what's missing is this issues. Has there been any progress? Thanks in advance!

Julien Duroure commented

2024-01-05 17:02:27 +01:00

There will be an experimental GN Instance export on 4.1 (with or without using gpu instancing).
So I think we can close this ticket now.
Thanks!

There will be an experimental GN Instance export on 4.1 (with or without using gpu instancing). So I think we can close this ticket now. Thanks!

Julien Duroure closed this issue

2024-01-05 17:02:30 +01:00

Blender Bot added

and removed