Unlink materials of instanced asset?

[jimbz]

Hi,

Thank you for the good work in making Filament powerful and lightweight.

I have an asset with many instances (AssetLoader.createInstancedAsset), and I realized that all the assets share the same material instance. Is is possible to "unlink" those instances so that their parameters can be updated independently?

I tried something like this:

                    val material = renderableManager.getMaterialInstanceAt(
                        renderableInstance,
                        primitiveIndex
                    ).material

                    val materialInstance = material.createInstance()

                    renderableManager.setMaterialInstanceAt(
                        renderableInstance,
                        primitiveIndex,
                        materialInstance
                    )

which builds and runs but does not seem to preserve the original parameters (the materials become invisible).

It is possible I did something wrong but I would like confirmation that my mental model of the materials and material instances is correct in the context of an instanced assets.

Thank you!

[romainguy]

What you did is correct, unfortunately an instance only gets its default parameters from the material, and it seems like we only set parameters on instances in gltfio.

@prideout Do you think we could set default parameters on materials for gltfio? Not clear if it makes sense or not but it sound like it could be useful for cases like this.

[jimbz]

@prideout I need to change only a single parameter, while preserving the other ones. In this case it's actually a new opacity parameter that I added locally inside gltfio but I could see use cases with changing existing parameters like the color for example.

I am using asyncBeginLoad but my models are not texture-heavy so I think I could easily switch to loadResources.

[prideout]

As an experiment you can try switching to loadResources to see if that fixes your disappearing mesh issue. The big comment block in AssetLoader.java shows how to do this. (note the use of addEntities rather than popRenderables)

[jimbz]

No luck... So are you saying that the default parameters are indeed set on the gltfio materials so creating and using a new instance like I did, without changing any parameter should in theory look the same?

[prideout]

Well you'd still need to set up every parameter. I'm starting to see what Romain was saying now, especially since it sounds like your your mesh is disappearing due to opacity.

I'm just not sure that setting up default parameters are what you want, since gltfio can use the same base material to create many different material instances, each of which is customized by various glTF nodes. Seems like you really need the getParameter stuff that Romain was alluding to, or a new clone() method proffered by MaterialInstance.

[jimbz]

Gotcha, the materials are reused between assets which is why the default parameters do not make sense indeed. I will look into cloning instances using the getParameter PR.

Thank you for taking the time to walk me through the situation!