oh, some addition. i understood your problem then you could have 2 different colors in the checker but not 2 different transparency settings. you could mix 2 materials in the checker, but that is not a good thing to do. mix the textures before you create a material. and having a checker that has 2 colors and 2 other values for transparency is not possible with one checker. so i showed you how to use 2 checkers. and the result is all transparent, because i used 4 colors that are all other than black. actually i painted them in photoshop and checked every pixel so it had the same color