If ParamBrowLY si ParamBrowRY are 0, then the opacity will be set to 0 > default position For example, a general use-case is the BrowUP/Down animations for 3D, and for 2D ParamBrowLY, ParamBrowRY animations - surprise & frowning.
It's important that the Live2D (Cubism) assets that are used for animated textures have their parameters named correctly for the behavior you want to obtain. These animated textures for normal maps built with Live2D (Cubism) assets work in synergy with the tracked animation inputs of the avatar. It’s a great way to accentuate the avatar’s expressivity without increasing the polycount The animated textures, if used for Normal Maps, are used for dynamically enhancing the details on the avatar's normals. Having a correct (static) texture as a base is still important!
The Live2D (Cubism) animated textures details are alpha-blended on top of the existing static textures, and the result of this blend is what is used on the model.