Add Custom material

[abren93]

I'm trying to overwrite the material like this:

const contentContainer = new ThreeMeshUI.Block({...});
contentContainer.backgroundMaterial = myShaderMaterial;
contentContainer.backgroundMaterial.needsUpdate = true;
contentContainer.updateBackgroundMaterial();
contentContainer.update();
ThreeMeshUI.update();

Doesn't work. How can I overwrite the material? Thank you