Creating a Custom Terrain Shader in Unity

In this tutorial, we will create a custom terrain shader in Unity to give your terrain more realistic textures and lighting. This approach allows for better performance and control over how the terrain interacts with lights, shadows, and other environmental effects. We will cover setting up the shader, using it with Unity's terrain system, and making adjustments for optimal performance.

1. Setting Up the Terrain

Before diving into the shader creation, let's first set up the terrain in Unity:

1. In Unity, go to the GameObject menu and select 3D Object > Terrain.
2. This will add a new Terrain object to your scene. You can adjust its size, height, and other settings in the Terrain Inspector.
3. Once the terrain is created, you can paint on it using the Paint Texture tool in the Inspector. But for now, leave it blank as we will apply a custom shader.

2. Creating the Terrain Shader

Now let's create the custom terrain shader. Follow these steps:

1. Right-click in the Project window and choose Create > Shader > Standard Surface Shader.
2. Name the shader CustomTerrainShader and open it in your preferred code editor.

Replace the default shader code with the following:

Shader "Custom/TerrainShader"
{
    Properties
    {
        _MainTex ("Base (RGB)", 2D) = "white" {}
        _BumpMap ("Normal Map", 2D) = "bump" {}
        _Specular ("Specular", Color) = (0.2, 0.2, 0.2, 1)
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 200

        CGPROGRAM
        #pragma surface surf Standard fullforwardshadows

        sampler2D _MainTex;
        sampler2D _BumpMap;
        fixed4 _Specular;

        struct Input
        {
            float2 uv_MainTex;
            float3 worldNormal;
        };

        void surf (Input IN, inout SurfaceOutputStandard o)
        {
            fixed4 c = tex2D(_MainTex, IN.uv_MainTex);
            o.Albedo = c.rgb;
            o.Normal = UnpackNormal(tex2D(_BumpMap, IN.uv_MainTex));
            o.Specular = _Specular;
            o.Smoothness = 0.5;
        }
        ENDCG
    }
    FallBack "Diffuse"
}

3. Applying the Shader to the Terrain

After creating the shader, you need to apply it to the terrain material:

• Right-click in the Project window and select Create > Material. Name this material TerrainMaterial.
• In the Material Inspector, click on the Shader dropdown and choose Custom > TerrainShader.
• Assign textures for the MainTex and BumpMap in the Material Inspector.
• Now, assign this material to your terrain by selecting the Terrain object, going to the Terrain Inspector, and setting the TerrainMaterial under the Materials section.

4. Tweaking the Shader for Performance

To ensure the shader runs smoothly, especially on large terrains, we can tweak a few settings:

• Lower the resolution of the normal map or use a simplified one to reduce GPU load.
• Disable any features of the shader that you aren't using (like parallax mapping or additional lighting effects).
• Use Unity's built-in Terrain LOD system to dynamically adjust the level of detail on distant parts of the terrain.

5. Final Adjustments and Testing

Once the shader is applied and the terrain is set up, test it in different lighting conditions. You can adjust the Specular and Smoothness properties of the shader to see how they affect the overall look of your terrain in various environments.

Conclusion

With a custom terrain shader, you can enhance the visual fidelity of your terrains while maintaining control over performance. Feel free to expand on this shader by adding additional features like detail textures, triplanar mapping, or tessellation.