Terrain Shader with snow - help request

Unity Engine
1

Hi, me again…

I’m writing a terrain snow shader, but I’m having some problems with the snow texture. I think it’s being spread across the entire map, rather than tiling as I’d like it to. My other issue is trying to tone it down a bit, so that it’s not quite so stark.

Other than that, here we have a replacement shader for terrains, with normal mapping and separate snow mapping system…
I’ve called it “snow” but it will happily do mud or sand for various purposes.

Shader "Custom/FE_Terrain_Pass1"
{
	Properties
	{
		_Control ("Control (RGBA)", 2D) = "red" {}
		_Splat3 ("Layer 3 (A)", 2D) = "white" {}
		_Splat2 ("Layer 2 (B)", 2D) = "white" {}
		_Splat1 ("Layer 1 (G)", 2D) = "white" {}
		_Splat0 ("Layer 0 (R)", 2D) = "white" {}
		_SnowNormTex ("Snow Normal Map", 2D) = "black" {}
		_SnowColor ("Snow Colour", Color) = (1, 1, 1, 1)
		_SnowAmount ("Snow Amount", Range(0, 1)) = 0
	}


	SubShader
	{
		Tags
		{
			"SplatCount" = "4"
			"Queue" = "Geometry-100"
			"RenderType" = "Opaque"
		}

		CGPROGRAM
		#pragma surface surf Lambert vertex:vert
		#pragma target 3.0
		#include "UnityCG.cginc"

		struct Input
		{
			float3 worldPos;
			float2 uv_Control : TEXCOORD0;
			float2 uv_Splat0 : TEXCOORD1;
			float2 uv_Splat1 : TEXCOORD2;
			float2 uv_Splat2 : TEXCOORD3;
			float2 uv_Splat3 : TEXCOORD4;
			float2 uv_SnowNormTex;
			fixed4 color : COLOR;

		};

		// Supply the shader with tangents for the terrain
		void vert (inout appdata_full v)
		{
			// A general tangent estimation	
			float3 T1 = float3(1, 0, 1);
			float3 Bi = cross(T1, v.normal);
			float3 newTangent = cross(v.normal, Bi);
			normalize(newTangent);
			v.tangent.xyz = newTangent.xyz;
			if (dot(cross(v.normal,newTangent),Bi) < 0)
				v.tangent.w = -1.0f;
			else
				v.tangent.w = 1.0f;
		}
		
		sampler2D _Control;
		sampler2D _BumpMap0, _BumpMap1, _BumpMap2, _BumpMap3;
		sampler2D _Splat0, _Splat1, _Splat2, _Splat3;
		float _Tile0, _Tile1, _Tile2, _Tile3, _TerrainX, _TerrainZ;
		float4 _v4CameraPos;
		sampler2D _SnowNormTex;
		float _SnowAmount;
		float4 _SnowColor;


		void surf (Input IN, inout SurfaceOutput o) {
		
			half4 splat_control = tex2D (_Control, IN.uv_Control);
			half3 pixcolor;
			
			// first texture which is usually some kind of rock texture gets mixed with itself
			// see: http://forum.unity3d.com/threads/116509-Improved-Terrain-Texture-Tiling 	
			pixcolor = splat_control.r * tex2D (_Splat0, IN.uv_Splat0).rgb * tex2D (_Splat0, IN.uv_Splat0 * -0.125).rgb * 4;
			o.Normal = splat_control.r * UnpackNormal(tex2D(_BumpMap0, float2(IN.uv_Control.x * (_TerrainX/_Tile0), IN.uv_Control.y * (_TerrainZ/_Tile0))));
		
			pixcolor += splat_control.g * tex2D (_Splat1, IN.uv_Splat1).rgb;
			o.Normal += splat_control.g * UnpackNormal(tex2D(_BumpMap1, float2(IN.uv_Control.x * (_TerrainX/_Tile1), IN.uv_Control.y * (_TerrainZ/_Tile1))));
			
			pixcolor += splat_control.b * tex2D (_Splat2, IN.uv_Splat2).rgb;
			o.Normal += splat_control.b * UnpackNormal(tex2D(_BumpMap2, float2(IN.uv_Control.x * (_TerrainX/_Tile2), IN.uv_Control.y * (_TerrainZ/_Tile2))));
			
			pixcolor += splat_control.a * tex2D (_Splat3, IN.uv_Splat3).rgb;
			o.Normal += splat_control.a * UnpackNormal(tex2D(_BumpMap3, float2(IN.uv_Control.x * (_TerrainX/_Tile3), IN.uv_Control.y * (_TerrainZ/_Tile3))));
			
			// blend the pixel colour with the snow (if required)
			if(WorldNormalVector(IN, o.Normal.y) > lerp(1, -1, _SnowAmount))
			{
				o.Albedo.rgb = _SnowColor.rgb;
				o.Normal = UnpackNormal (tex2D (_SnowNormTex, IN.uv_SnowNormTex));
			} else {
				o.Albedo.rgb = pixcolor.rgb;
			}
			o.Alpha = 0;
		}
		
		ENDCG  
	}

	//Dependency "AddPassShader" = "Custom/FE_Terrain_Pass2"
	Dependency "BaseMapShader" = "Diffuse"

	// Fallback to Diffuse
	Fallback "Diffuse"
}
2

Well, yeah it’s spread across the terrain because you’re using the Terrain’s raw UV map.
With each of the splatmaps, Unity’s terrain system sets the tiling of the splat texture. However, it has no idea about your snow texture so it doesn’t set the tiling. You’d have to do this yourself.

Otherwise, nice shader. Think I might borrow an idea or two for the weather system I’m working on.