add note on unloading dynamically generated meshes

[Bersaelor]

I noticed some major memory leaks after loading and unloading many small gltf's in our Unity app.
Our app is basically a browser for gltf files stored in the backend.

After adding the mentioned lines, I was able to keep the memory usage to the gltf files currently shown in the scene, which is especially important for cheaper android devices where memory isn't as big.

Since I spent a while figuring out what had happened, I thought it maybe helpful for other people importing meshes at runtime?

[atteneder]

Hi @Bersaelor ,

Thanks a lot for sharing this!

I'm curious, did you try GltfImport.Dispose and did it work for you?

The proposed solution, while working and generic, might have downsides:

• Accessing .mesh after destroying .sharedMesh (which is not done immediately) might trigger cloning the sharedMesh again.
• GetComponentsInChildren is not best practice (slow)

I'd suggest to create a more specific solution to the problem. I think GltfImport.Dispose ultimately should handle this.

[Bersaelor]

I'd suggest to create a more specific solution to the problem. I think GltfImport.Dispose ultimately should handle this.

Mhmm, I'm not sure how I can use that, I thought the GltfImport is only used to import the asset and not needed anymore afterwards? I.e. after running gltf.InstantiateMainScene(transform) I don't need to hold a reference to the GltfImport class anymore?

So, I'll try keeping a reference to my GltfImport around and use GltfImport.Dispose() when I want to remove the 3D asset from the scene and check the memory imprint.

[Bersaelor]

Alright, replaced the destroying of the meshes with a reference

        private GltfImport? importer;

and when unloading I now call Dispose()

        public void unloadContent()
        {
            if (!isLoaded)
                return;

            if (importer != null)
                importer.Dispose();

            foreach (Transform child in transform)
                GameObject.Destroy(child.gameObject);
        }

which works. Thank you @atteneder . Maybe instead of the proposed PR note, we should put a note in the documentation reminding people to use importer.Dispose()? if we use a custom method with gltfImport or is this something more experienced Unity devs would assume naturally?

[atteneder]

I made this paragraph now, which makes this PR obsolete.

Thanks for bringing it up!