Vertex displacement shader troubles

[VivienS]

Hi there!

I want to write a surface shader that does vertex displacement and unculled cutout shading.

The code is very simple, as you can see below. There’s a vertex function for the displacement and a surface function for the shading.

Unfortunately the shader behaves wrong when it’s asked to cast shadows. It seems it takes the solid, un-deformed geometry aswell as the deformed one for shadow calculations. The two sometimes even cast shadows on each other. (see the screenshots).

How can I get only the deformed cutout part to cast shadows?

Thanks!

Shader "Transparent/Cutout/Diffuse Wiggle" {
Properties {
	_Color ("_Color", Color) = (1,1,1,1)
	_MainTex ("_MainTex", 2D) = "white" {}
	_Amount ("_Amount", Range(0,.2)) = 0.1
	_Direction ("_Direction", Vector) = (0,0,0,0)
	_Scale ("_Scale", Range(0.1,10)) = 1.0
	_TimeScale ("_TimeScale", Range(0,10)) = 1.0
	_Cutoff ("_Cutoff", Range (0,1)) = 0.5
}

SubShader {
	Tags { "RenderType" = "Opaque" "Queue" = "Transparent" }
	Cull Off

	CGPROGRAM
	#pragma surface surf Lambert vertex:vert addshadow alphatest:_Cutoff 

	struct Input {
		float2 uv_MainTex;
	};

	half4 _Direction;
	float _Amount;
	float _TimeScale;
	float _Scale;
	sampler2D _MainTex;
	half4 _Color;

	void vert(inout appdata_full v)	{
		// calculate offset amount
		float4 offs = float4 (normalize(v.normal), 0) * sin (_Time.y * _TimeScale + (v.vertex.y * _Scale)) * _Amount;

		// offset vertex
		v.vertex += offs * _Direction;
	}

	void surf (Input IN, inout SurfaceOutput o) {
		half4 c = tex2D (_MainTex, IN.uv_MainTex);
		o.Albedo = c.rgb * _Color.rgb;
		o.Alpha = c.a * _Color.a;
	}
	ENDCG
}
Fallback "Transparent/Cutout/Diffuse"

}

[ScroodgeM]

Shader "Unity Answers/Alpha clipped model"
{
	Properties
	{
		_Color ("_Color", Color) = (1,1,1,1)
		_MainTex ("_MainTex", 2D) = "white" {}
		_Amount ("_Amount", Range(0,.2)) = 0.1
		_Direction ("_Direction", Vector) = (0,0,0,0)
		_Scale ("_Scale", Range(0.1,10)) = 1.0
		_TimeScale ("_TimeScale", Range(0,10)) = 1.0
		_Cutoff ("_Cutoff", Range (0,1)) = 0.5
	}
	SubShader
	{
		Cull Off

		CGPROGRAM
		#pragma surface surf LambertDoubleSided vertex:vert addshadow alphatest:_Cutoff 

		struct Input
		{
			float2 uv_MainTex;
		};

		half4 _Direction;
		float _Amount;
		float _TimeScale;
		float _Scale;
		sampler2D _MainTex;
		half4 _Color;

		void vert(inout appdata_full v)
		{
			float4 offs = float4 (normalize(v.normal), 0) * sin (_Time.y * _TimeScale + (v.vertex.y * _Scale)) * _Amount;
			v.vertex += offs * _Direction;
		}

		void surf (Input IN, inout SurfaceOutput o) {
			half4 c = tex2D (_MainTex, IN.uv_MainTex);
			o.Albedo = c.rgb * _Color.rgb;
			o.Alpha = c.a * _Color.a;
		}

		fixed4 LightingLambertDoubleSided (SurfaceOutput s, fixed3 lightDir, fixed atten)
		{
			fixed diff = abs ( dot (s.Normal, lightDir));
	
			fixed4 c;
			c.rgb = s.Albedo * _LightColor0.rgb * (diff * atten * 2);
			c.a = s.Alpha;
			return c;
		}
	
		ENDCG
	}
	Fallback "Transparent/Cutout/Diffuse"
}