GrabPassSphere.shader

Shader "Custom/GrabPassSphere"
{
	Properties
	{
		_Length ("Length", Range(0,1)) = .5
		_Strength ("Strength", Range(0, 1000.)) = 0.01
	}

	SubShader
	{
		Lighting Off
		Tags { "Queue" = "Transparent" "RenderType"="Opaque" }
		GrabPass { "_GrabTexture" }
		ColorMask 0
		ZWrite On

		CGPROGRAM
		#pragma surface surf NoLighting vertex:vert alpha:blend novertexlights

		half4 LightingNoLighting(SurfaceOutput s, half3 lightDir, half atten)
		{
			half4 c;
			c.rgb = s.Albedo.rgb;
			c.a = s.Alpha;

			return c;
		}

		struct Input
		{
			float3 viewDir;
			float4 grabUV;
		};

		void vert (inout appdata_full v, out Input o)
		{
			o.viewDir = ObjSpaceViewDir(v.vertex);
			o.grabUV = ComputeGrabScreenPos(UnityObjectToClipPos(v.vertex));
		}

		sampler2D _GrabTexture;
		uniform float _Length;
		uniform float _Strength;

		void surf (Input IN, inout SurfaceOutput o)
		{
			o.Specular = 0;
			o.Emission = 0;
			float vertLen = 1.0 - saturate (dot (normalize (IN.viewDir), o.Normal));
			float4 fix = ComputeScreenPos (UnityObjectToClipPos (float3(0, 0, 0)));
			fixed2 pos = IN.grabUV - fix;
			float expLen = exp (-_Strength * pow(vertLen - _Length, 2));
			float th = expLen * sin(_Length * 3.141593 * .015) * (8.0 - 8.0 * pow(_Length, 2.0/3.0));
			float sinTh = sin(th);
			float cosTh = cos(th);
			IN.grabUV.x = pos.x * cosTh - pos.y * sinTh + fix.x;
			IN.grabUV.y = pos.x * sinTh + pos.y * cosTh + fix.y;

			o.Albedo = tex2Dproj (_GrabTexture, IN.grabUV);
			o.Alpha = 1.0 - _Length;
		}
		ENDCG

	}
}