I was able to just update the terrainShader.xml with the latest version and it works fine.
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Navigate to the installed game directory and open the data folder, then open the shaders folder and just copy the terrainShader.xml DO NOT OPEN OR EDIT IT IN ANY WAY! Next you need to unzip the modmap in your mods folder and navigate to the folder called data, I believe, its the folder where all the shader files are located. Then paste the updated terrainShader.xlm to overwrite the old one. Rezip the mod making sure to name it exactly the same as the original and then place it back in your mods folder to overwrite to original. Load the game and your golden. Good luck.