Rolling.shader

Shader "Custom/Rolling"
{
	Properties
	{
	_MainTex("Base (RGB)", 2D) = "white" {}
	_Bend("Bend",Float) = 1
	_Strength("Strength",Float) = 1
	}

		SubShader
	{
	Tags {"Queue" = "Geometry" "IgnoreProjector" = "true" "RenderType" = "Opaque"}
	Cull Off

	Pass
	{
	CGPROGRAM
	#pragma vertex vert
	#pragma fragment frag
	#include "UnityCG.cginc"

	struct v2f
	{
	half2 texcoord  : TEXCOORD0;
	float4 vertex   : SV_POSITION;
	};

	sampler2D _MainTex;
	float _Bend;
	float _Strength;

	v2f vert(appdata_full v)
	{
	v2f o;

	//I don't know what should I write here for rolling ,please help me.
	//v.vertex.y *= ???
	v.vertex.y *= exp(_Bend + (v.vertex.x*_Strength)); // something like this but this hasn't twist effect
	o.vertex = UnityObjectToClipPos(v.vertex);
	o.texcoord = v.texcoord;
	return o;
	}

	float4 frag(v2f i) : COLOR
	{

	float2 uv = i.texcoord.xy;
	float4 tex = tex2D(_MainTex, uv);

	return tex;
	}
	ENDCG
	}
	}
		Fallback Off
}