The Opacity input is used when using the Translucent Blend Mode, typically for Translucent, Additive, and Modulated materials. You can input a value between 0 and 1, where:
- 0.0 represents completely transparent.
- 1.0 represents fully opaque.
Opaque and masked blend modes also use Opacity when using one of the subsurface shading models.
Opacity is mostly used for Translucent, Additive, and Modulated Materials.