Add Smoothness value to a Shader

Questions & Answers
1

This is the Unity Standard Terrain Shader source code, I’m trying to add a smoothness value so I can change the entire terrain smoothness via script, this to make the terrain look’s wet, I try this but it give me an error. What can be? Thanks.

Shader "Nature/Terrain" {
    Properties {
        [HideInInspector] _Control ("Control (RGBA)", 2D) = "red" {}
        [HideInInspector] _Splat3 ("Layer 3 (A)", 2D) = "white" {}
        [HideInInspector] _Splat2 ("Layer 2 (B)", 2D) = "white" {}
        [HideInInspector] _Splat1 ("Layer 1 (G)", 2D) = "white" {}
        [HideInInspector] _Splat0 ("Layer 0 (R)", 2D) = "white" {}
        [HideInInspector] _Normal3 ("Normal 3 (A)", 2D) = "bump" {}
        [HideInInspector] _Normal2 ("Normal 2 (B)", 2D) = "bump" {}
        [HideInInspector] _Normal1 ("Normal 1 (G)", 2D) = "bump" {}
        [HideInInspector] _Normal0 ("Normal 0 (R)", 2D) = "bump" {}
        // used in fallback on old cards & base map
        [HideInInspector] _MainTex ("BaseMap (RGB)", 2D) = "white" {}
        [HideInInspector] _Color ("Main Color", Color) = (1,1,1,1)

        _Glossiness ("Smoothness", Range(0,1)) = 0.5 // NEW LINE
    }

    CGINCLUDE
        #pragma surface surf Lambert vertex:SplatmapVert finalcolor:SplatmapFinalColor finalprepass:SplatmapFinalPrepass finalgbuffer:SplatmapFinalGBuffer noinstancing
        #pragma multi_compile_fog
        #include "TerrainSplatmapCommon.cginc"

        void surf(Input IN, inout SurfaceOutput o)
        {
            half4 splat_control;
            half weight;

            half _Glossiness; // NEW LINE

            fixed4 mixedDiffuse;
            SplatmapMix(IN, splat_control, weight, mixedDiffuse, o.Normal);
            o.Albedo = mixedDiffuse.rgb;
            o.Alpha = weight;

            o.Smoothness = _Glossiness; // NEW LINE
        }
    ENDCG

    Category {
        Tags {
            "Queue" = "Geometry-99"
            "RenderType" = "Opaque"
        }

        // TODO: Seems like "#pragma target 3.0 _TERRAIN_NORMAL_MAP" can't fallback correctly on less capable devices?
        // Use two sub-shaders to simulate different features for different targets and still fallback correctly.
        SubShader { // for sm3.0+ targets
            CGPROGRAM
                #pragma target 3.0
                #pragma multi_compile __ _TERRAIN_NORMAL_MAP
            ENDCG
        }
        SubShader { // for sm2.0 targets
            CGPROGRAM
            ENDCG
        }
    }

    Dependency "AddPassShader" = "Hidden/TerrainEngine/Splatmap/Diffuse-AddPass"
    Dependency "BaseMapShader" = "Diffuse"
    Dependency "Details0"      = "Hidden/TerrainEngine/Details/Vertexlit"
    Dependency "Details1"      = "Hidden/TerrainEngine/Details/WavingDoublePass"
    Dependency "Details2"      = "Hidden/TerrainEngine/Details/BillboardWavingDoublePass"
    Dependency "Tree0"         = "Hidden/TerrainEngine/BillboardTree"

    Fallback "Diffuse"
}
2

You need to define the shader property as a uniform outside of the surface function itself;

#include "TerrainSplatmapCommon.cginc"

half _Glossiness; // NEW LINE
 
void surf(Input IN, inout SurfaceOutput o)
{
    half4 splat_control;
    half weight;
    fixed4 mixedDiffuse;
    SplatmapMix(IN, splat_control, weight, mixedDiffuse, o.Normal);
    o.Albedo = mixedDiffuse.rgb;
    o.Alpha = weight;
    o.Smoothness = _Glossiness; // NEW LINE
}

This may not work the way you expect though - in order for terrains to support the number of textures they do, the shader itself is split into multiple passes; each additional pass will use the “AddPassShader” listed at the bottom.