How to set transparency of a FilamentAsset.

[JackKaiXing]

here is the question.

Our project need fade in/out effects for glTF models loaded by gltfio, i.e. a FilamentAsset object. How can I set the transparency of a FilamentAsset object.

auto rcm = m_engine->rcm();
auto entities = m_asset->getEntities();
auto count = m_asset->getEntityCount();

for (uint32_t index = 0; index < count; index++)
{
        auto instance = m_engine->rcm()->getInstance(entities[index]);
	if (instance.isValid())
	{
		uint32_t count = rcm->getPrimitiveCount(instance);
		for (uint32_t pIndex = 0; pIndex < count; pIndex ++)
		{
			MaterialInstance* mi = rcm->getMaterialInstanceAt(instance, pIndex);
                        
                        mi->setParameter(WHAT_NAME,0.5f); // how to set transparency here?
		}
	}
}

[JackKaiXing]

my materialProvider is gltfio::createUberShaderLoader();

[JackKaiXing]

@bejado

I think, mi->setParameter("baseColorFactor", my_vector) would overwrite the initial factor for rgb component, however alpha is the only thing I wanna to change.

[JackKaiXing]

@romainguy @bejado

I am running into another problem about transparency.

For a single glTF file, which is consisted of several parts. I set this glTF file to be 0.5f transparency.

However, it flickers as the drawing order of each part is not fixed.

Any ideas? setBlendOrderAt seems to work?

[JackKaiXing]

@romainguy @bejado

setBlendOrderAt works for my case. Thanks.

However, I got another question.

How could I get the value of a parameter for current materialInstance?

[bejado]

We don't provide an API to get the current value of a parameter; it's up to the application itself to track this information.

[CallumHoughton]

I would also like to know the best way to go about doing this. I load .glb files, and the user can choose their own models to view so it isn't feasible to keep track of material parameters. Is there any other way around this?