Add shaders

Sources/Shaders/SnowedTreeBillboard.cginc

@@ -0,0 +1,36 @@
+	
+	uniform float4    _GS_SnowData1;	// x = relief, y = occlusion, z = glitter, w = brightness
+	uniform float4    _GS_SnowData2;	// x = minimum altitude for vegetation
+	uniform float4    _GS_SnowData4;    // w = billboard coverage
+    uniform float4    _GS_SnowCamPos;
+    unfiorm half4     _GS_SnowTint;
+    uniform sampler2D_float _GS_DepthTexture;
+
+	struct v2f {
+		float4 pos : SV_POSITION;
+		float3 worldPos : TEXCOORD0;
+		float2 uv: TEXCOORD1;
+	};
+
+
+	// get snow coverage on tree billboards
+	void SetTreeBillboardCoverage(v2f input, inout fixed4 col) { 
+		
+		float minAltitude = saturate((input.worldPos.y - _GS_SnowData2.x) * 0.1);
+		float solid       = col.g * 2.0 - _GS_SnowData4.w;
+		float snowCover   = minAltitude * saturate(solid) * 0.95;
+
+        // mask support
+        #if defined(GLOBALSNOW_MASK)
+            float4 st = float4(input.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
+		col.rgb = (1.0 + col.g) * (0.25 + _GS_SnowData1.w) * solid;
+        col.rgb *= _GS_SnowTint.rgb;
+		col.a   = snowCover;
+	}