Ch6StainedGlass1.shader

Shader "CookbookShaders/Ch06/StainedGlass" 
{
	Properties
	{
		_MainTex ("Base (RGBA)", 2D) = "white" {}
		_BumpMap ("Noise Texture", 2D) = "bump" {}
		_Magnitude("Magnitude", Range(0,1)) = 0.05
	}

	SubShader
	{
		Tags
		{
			"Queue" = "Transparent"
			"IgnoreProjector" = "True"
			"RenderType" = "Opaque"
		}

		ZWrite On Lighting Off Cull Off Fog{ Mode Off } Blend One Zero

		GrabPass {}	// first pass is a grab pass

		Pass		// rest of the code is in the second pass
		{
			CGPROGRAM

			#pragma vertex vert
			#pragma fragment frag
			#include "UnityCG.cginc"

			sampler2D _MainTex;
			sampler2D _BumpMap;
			float _Magnitude;

			sampler2D _GrabTexture;	// automatically generated by the GrabPass

			struct vertInput
			{
				float4 vertex : POSITION;
				float2 texcoord : TEXCOORD0;
			};

			struct vertOutput
			{
				float4 vertex : POSITION;
				float2 texcoord : TEXCOORD0;
				float4 uvgrab : TEXCOORD1;
			};

			vertOutput vert(vertInput v)
			{
				vertOutput o;
				o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
				o.texcoord = v.texcoord;
				o.uvgrab = ComputeGrabScreenPos(o.vertex);	// grab screen texture
				return o;
			}

			half4 frag(vertOutput i) : COLOR
			{
				half4 mainColor = tex2D(_MainTex, i.texcoord);

				half4 bump = tex2D(_BumpMap, i.texcoord);
				half2 distortion = UnpackNormal(bump).rg;

				i.uvgrab.xy += distortion * _Magnitude;	// distortion: offset the UV data of the grab texture

				fixed4 col = tex2Dproj(_GrabTexture, UNITY_PROJ_COORD(i.uvgrab));	// apply the screen texture in the correct position
				return col * mainColor;
			}

			ENDCG
		}
	}
}