liquid.shader

Shader "Unlit/SpecialFX/Liquid"
{
    Properties
    {
        _Tint ("Tint", Color) = (1,1,1,1)
        _MainTex ("Texture", 2D) = "white" {}
        _FillAmount ("Fill Amount", Range(-10,10)) = 0.0
        [HideInInspector] _WobbleX ("WobbleX", Range(-1,1)) = 0.0
        [HideInInspector] _WobbleZ ("WobbleZ", Range(-1,1)) = 0.0
        _TopColor ("Top Color", Color) = (1,1,1,1)
        _FoamColor ("Foam Line Color", Color) = (1,1,1,1)
        _Rim ("Foam Line Width", Range(0,0.1)) = 0.0
        _RimColor ("Rim Color", Color) = (1,1,1,1)
        _RimPower ("Rim Power", Range(0,10)) = 0.0
    }

    SubShader
    {
        Tags {"Queue"="Geometry"  "DisableBatching" = "True" }

                Pass
        {
         Zwrite On
         Cull Off // we want the front and back faces
         AlphaToMask On // transparency

         CGPROGRAM


         #pragma vertex vert
         #pragma fragment frag
         // make fog work
         #pragma multi_compile_fog

         #include "UnityCG.cginc"

         struct appdata
         {
           float4 vertex : POSITION;
           float2 uv : TEXCOORD0;
           float3 normal : NORMAL;
         };

         struct v2f
         {
            float2 uv : TEXCOORD0;
            UNITY_FOG_COORDS(1)
            float4 vertex : SV_POSITION;
            float3 viewDir : COLOR;
            float3 normal : COLOR2;
            float fillEdge : TEXCOORD2;
         };

         sampler2D _MainTex;
         float4 _MainTex_ST;
         float _FillAmount, _WobbleX, _WobbleZ;
         float4 _TopColor, _RimColor, _FoamColor, _Tint;
         float _Rim, _RimPower;

         float4 RotateAroundYInDegrees (float4 vertex, float degrees)
         {
            float alpha = degrees * UNITY_PI / 180;
            float sina, cosa;
            sincos(alpha, sina, cosa);
            float2x2 m = float2x2(cosa, sina, -sina, cosa);
            return float4(vertex.yz , mul(m, vertex.xz)).xzyw ;
         }


         v2f vert (appdata v)
         {
            v2f o;

            o.vertex = UnityObjectToClipPos(v.vertex);
            o.uv = TRANSFORM_TEX(v.uv, _MainTex);
            UNITY_TRANSFER_FOG(o,o.vertex);
            // get world position of the vertex
            float3 worldPos = mul (unity_ObjectToWorld, v.vertex.xyz);
            // rotate it around XY
            float3 worldPosX= RotateAroundYInDegrees(float4(worldPos,0),360);
            // rotate around XZ
            float3 worldPosZ = float3 (worldPosX.y, worldPosX.z, worldPosX.x);
            // combine rotations with worldPos, based on sine wave from script
            float3 worldPosAdjusted = worldPos + (worldPosX  * _WobbleX)+ (worldPosZ* _WobbleZ);
            // how high up the liquid is
            o.fillEdge =  worldPosAdjusted.y + _FillAmount;

            o.viewDir = normalize(ObjSpaceViewDir(v.vertex));
            o.normal = v.normal;
            return o;
         }

         fixed4 frag (v2f i, fixed facing : VFACE) : SV_Target
         {
           // sample the texture
           fixed4 col = tex2D(_MainTex, i.uv) * _Tint;
           // apply fog
           UNITY_APPLY_FOG(i.fogCoord, col);

           // rim light
           float dotProduct = 1 - pow(dot(i.normal, i.viewDir), _RimPower);
           float4 RimResult = smoothstep(0.5, 1.0, dotProduct);
           RimResult *= _RimColor;

           // foam edge
           float4 foam = ( step(i.fillEdge, 0.5) - step(i.fillEdge, (0.5 - _Rim)))  ;
           float4 foamColored = foam * (_FoamColor * 0.9);
           // rest of the liquid
           float4 result = step(i.fillEdge, 0.5) - foam;
           float4 resultColored = result * col;
           // both together, with the texture
           float4 finalResult = resultColored + foamColored;
           finalResult.rgb += RimResult;

           // color of backfaces/ top
           float4 topColor = _TopColor * (foam + result);
           //VFACE returns positive for front facing, negative for backfacing
           return facing > 0 ? finalResult: topColor;

         }
         ENDCG
        }

    }
}