Shader "Hidden/VolumetricFog2/Turbulence2D"
{
Properties {
    _MainTex ("Noise", 2D) = "white" {}
    _TurbulenceAmount ("Turbulence Amount", Float) = 0.5
}

SubShader {

    CGINCLUDE
    #include "UnityCG.cginc"

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

    struct v2f {
        float4 pos : SV_POSITION;
        float4 uv: TEXCOORD0;
    };
    
    sampler2D_float _MainTex;
    float _TurbulenceAmount;
    float _NoiseStrength, _NoiseFinalMultiplier;

    v2f vert(appdata v) {
        v2f o;
        o.pos = UnityObjectToClipPos(v.vertex);
        o.uv = float4(v.texcoord, 0, 0);
        return o;
    }   
    
    float4 frag(v2f i): SV_Target {
        float sint, cost;
        sincos(_TurbulenceAmount, sint, cost);
        float4 p0 = tex2Dlod(_MainTex, i.uv);
        float4 p1 = tex2Dlod(_MainTex, i.uv + float4(0.25,0.25,0,0));
        float  t0 = sint * 0.5 + 0.5;
        float4 r0 = lerp(p0, p1, t0);
        float4 p2 = tex2Dlod(_MainTex, i.uv + float4(0.5,0.5,0,0));
        float4 p3 = tex2Dlod(_MainTex, i.uv + float4(0.75,0.75,0,0));
        float  t1 = cost * 0.5 + 0.5;
        float4 r1 = lerp(p2, p3, t1);
        float  n  = 1.0 - max(r0, r1);
        n =  saturate( (1.0 - n * _NoiseStrength) * _NoiseFinalMultiplier);
        return n;
    }   
    
    
    ENDCG

    Pass { 
        ZTest Always Cull Off ZWrite Off
        CGPROGRAM
        #pragma target 3.0
        #pragma fragmentoption ARB_precision_hint_fastest
        #pragma vertex vert
        #pragma fragment frag
        ENDCG
    }
    
}

Fallback Off
}