Well, as I mentioned, NGUI's shaders are meant to work with widgets. Making them work with meshes involves custom code, like you've see in the other thread. If you can't use textures (and you don't need sprites, remember? you can just use regular textures with UITexture), and you have to use meshes, then you need to write a custom shader for it to make clipping possible. The key is that NGUI supplies variables to its own shaders that make clipping possible. You will need to do it yourself in an OnWillRenderObject().