There are two ways to layer textures in Maya: using the Layered Shader with the texture compositing flag or with the Layered Texture Node.
Though the workflow for using the Layered Texture node is similar to the Layered Shader, using the Layered Texture node.
The Layered Shader has an attribute called compositing flag that causes the shader type to layer materials or layer textures. You can use this to layer textures with the Layered Shader node. However, using the Layered Texture node is recommended because you can set many more options.
If you choose the texture option for the compositing flag, you must plug the whole network into a material (for example, Phong or Blinn).
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