Add shaders

Sources/Shaders/SnowedGrass.cginc

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+	uniform float4    _GS_SnowData1;	// x = relief, y = occlusion, z = glitter, w = brightness
+	uniform float4    _GS_SnowData2;	// x = minimum altitude, y = altitude scattering, z = coverage extension
+	uniform float4    _GS_SnowData3;	// x = Sun occlusion, y = sun atten, z = ground coverage, w = grass coverage
+    uniform float4    _GS_SnowCamPos;
+    uniform half4     _GS_SnowTint;
+    uniform sampler2D_float _GS_DepthTexture;
+    	
+struct Input {
+	float2 uv_MainTex;
+	fixed4 color : COLOR;
+	float3 worldPos;
+};
+
+
+	// get snow coverage on grass
+	void SetGrassCoverage(Input IN, inout SurfaceOutput o) { 
+		// prevent snow on sides and below minimum altitude
+		float minAltitude = saturate( IN.worldPos.y - _GS_SnowData2.x);
+		float snowCover   = minAltitude * saturate(IN.uv_MainTex.y + _GS_SnowData3.w);
+
+        // mask support
+        #if defined(GLOBALSNOW_MASK)
+            float4 st = float4(IN.worldPos.xz - _GS_SnowCamPos.xz, 0, 0);
+            st *= _GS_SnowData2.z;
+            st += 0.5;
+            float zmask = tex2Dlod(_GS_DepthTexture, st).g;
+            snowCover   = max(snowCover - zmask, 0);
+        #endif
+
+		// pass color data to output shader
+		o.Albedo = _GS_SnowData1.www;
+        o.Albedo.rgb *= _GS_SnowTint.rgb;
+		o.Alpha = snowCover * 0.96;
+	}
+	
+	
+