Liquid Shader

Shader "Custom/Liquid_Shader"
{
    Properties
    {
        [HDR]_TintColor("Color", Color) = (1,1,1,1)
        [HDR]_TopColor("TopColor", Color) = (1,1,1,1)
        _LiquidAmount("_Liquid Amount", Float) = 1

        _WorldLowestYPos("Liquid Bottom Y Pos", Float) = 0 //C#으로 부터 받은 가장 밑부분 vertex pos

        _BottleHeight("Bottle Height", Float) = 0
        _BottleWidth("Bottle Width", Float) = 0

        _WobbleX("WobbleX",Float) = 0
        _WobbleZ("WobbleZ",Float) = 0

        [Header(Rim)]
        _RimPower("Rim Power", Range(0.01, 2)) = 0.1
        [HDR]_RimColor("Rim Color", Color) = (1,1,1,1)
        _RimIntensity("Rim Intensity", Range(0.1, 100)) = 1
        [Header(Foam)]
        [HDR] _FoamColor("Foam Line Color", Color) = (1,1,1,1)
        _Line ("Foam Line Width", Range(0,3)) = 0.0
        _LineSmooth("Foam Line Smoothness", Range(0,3)) = 0.0
        _LineBk("Back Foam Width", Range(-2,0)) = 0
    }

    SubShader
    {
        Tags { "RenderType" = "Opaque" "RenderPipeline" = "UniversalPipeline" "Queue" = "Geometry" "DisableBatching" = "True"}

        Pass{

            Zwrite on
            Cull off
            AlphaToMask On //transparency ?

            HLSLPROGRAM

            #pragma vertex vert
            #pragma fragment frag

            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Lighting.hlsl"
            #pragma target 3.0


            struct Attributes
            {
                float4 positionOS       : POSITION;
                float3 normal           : NORMAL;
            };

            struct Varyings
            {
                float4 positionHCS      : SV_POSITION;
                float3 normal           : NORMAL;
                float3 positionWS       : TEXCOORD1;
                float3 liquidPosition   : TEXCOORD2;
                float3 normalizedDirY   : TEXCOORD3;
                float3 WSViewDir        : TEXCOORD4;
            };

            half4 _TintColor;
            half4 _TopColor;
            float _LiquidAmount;

            float _WorldLowestYPos; //C#
            float _LocalObjectNormal; //C#

            float _BottleWidth =1;
            float _BottleHeight = 2;

            float3 _LocalYDir; //C#

            float _WobbleX, _WobbleZ;


            float _RimPower,_RimIntensity;
            half3 _RimColor;
            half4 _FoamColor;
            float _Line, _LineSmooth;
            float _WSPosY;

            float _LineBk;


            float3 Unity_RotateAboutAxis_Degrees(float3 In, float3 Axis, float Rotation)
            {
                Rotation = radians(Rotation);
                float s = sin(Rotation);
                float c = cos(Rotation);
                float one_minus_c = 1.0 - c;

                Axis = normalize(Axis);
                float3x3 rot_mat =
                {   one_minus_c * Axis.x * Axis.x + c, one_minus_c * Axis.x * Axis.y - Axis.z * s, one_minus_c * Axis.z * Axis.x + Axis.y * s,
                    one_minus_c * Axis.x * Axis.y + Axis.z * s, one_minus_c * Axis.y * Axis.y + c, one_minus_c * Axis.y * Axis.z - Axis.x * s,
                    one_minus_c * Axis.z * Axis.x - Axis.y * s, one_minus_c * Axis.y * Axis.z + Axis.x * s, one_minus_c * Axis.z * Axis.z + c
                };
                float3 Out = mul(rot_mat,  In);
                return Out;
            }


            Varyings vert (Attributes IN )
            {
                Varyings OUT;
                OUT.positionHCS = TransformObjectToHClip(IN.positionOS.xyz);
                OUT.positionWS  = TransformObjectToWorld(IN.positionOS.xyz);
                OUT.normalizedDirY = normalize(float3(0, IN.positionOS.y ,0));
                float3 positionWS = mul(unity_ObjectToWorld, IN.positionOS.xyz);

                OUT.normal = TransformObjectToWorldNormal(IN.normal.xyz);
                OUT.WSViewDir = normalize(_WorldSpaceCameraPos.xyz - OUT.positionWS.xyz);

                // pos = worldPos(mesh center.xyz의미) - transform.position - new Vector3(0, fillAmount, 0); //C#
                //rend.sharedMaterial.SetVector("_FillAmount", pos); //C#


                // float3 worldPos = mul (unity_ObjectToWorld, v.vertex.xyz);
                //float3 worldPosOffset = float3(worldPos.x, worldPos.y , worldPos.z) - _FillAmount;

                    //float3 posWSX = Unity_RotateAboutAxis_Degrees(positionWS-IN.positionOS, float3(0,0,1), 90);
                //액체 회전 시키기   //변경하고자 하는 버텍스 포지션, 회전 기준 축 , 최대 각도 //90도로 해두어야 sin값을 곱했을 때 좌우 대칭으로 움직인다.
                //아니면 float3 (0,0,1)축을 음수버전을 만들어 주어야한다.
                float3 posWSX = Unity_RotateAboutAxis_Degrees(IN.positionOS, float3(0,0,1), 90); //IN.positionOS
                float3 posWSZ = Unity_RotateAboutAxis_Degrees(IN.positionOS, float3(1,0,0), 90);
                float3 worldPosAdjusted = OUT.positionWS +  (posWSX * _WobbleX) + (posWSZ * _WobbleZ);

                float dotNormal = dot(OUT.WSViewDir, OUT.normal);
                OUT.liquidPosition = worldPosAdjusted;  //-_LiquidAmount;
                if(dotNormal>=0)
                {
                    OUT.normal = OUT.normal;
                }
                else
                {
                    OUT.normal = float3(0,1,0);
                }


                return OUT;
            }

            half4 frag(Varyings IN, half facing:VFACE) : SV_Target
            {
                float3 worldYDir = float3(0,1,0);
                //물병과 world Y의 벌어진 각도 정도 float dotWorldContainer
                float dotWorldContainer =abs(dot(worldYDir.xyz,  _LocalYDir.xyz));
                //bottle의 가로 높이 비율에 따라 눕혔을 때의 액체의 높이 조절
                float liquidHeight = lerp(_LiquidAmount * _BottleWidth/_BottleHeight, _LiquidAmount, dotWorldContainer); //min, max, 1-0  dot abs
                //액체 y 값
                float liquidPosition = IN.liquidPosition.y - liquidHeight;  //IN.positionWS.y - _LiquidAmount;


                float cutoffTop = step(liquidPosition,  _WorldLowestYPos);

                //--Rim Light --------------------------------------
                half face = saturate(dot(IN.WSViewDir, IN.normal));
                half3 rim = 1.0 - (pow(face, _RimPower));
                ///-------------------------------------------------

                //--foam--------------------------------------------
                float LineUpdate = lerp(_Line * _BottleWidth/_BottleHeight, _Line, dotWorldContainer);
                float LineSmooth = lerp(_LineSmooth * _BottleWidth/_BottleHeight, _Line, dotWorldContainer);
                float foam = smoothstep(_WSPosY  - _Line - _LineSmooth, _WSPosY - _Line, liquidPosition); //liquidPosition
                float backfoam = smoothstep(_WSPosY-(_Line + _LineBk)-_LineSmooth, _WSPosY-(_Line+_LineBk),liquidPosition);
                ///-------------------------------------------------

                //물자르기 + 물 색
                half4 finalResult = _TintColor + foam *_FoamColor;//cutoffTop * _TintColor;
                finalResult.rgb += rim * _RimColor * _RimIntensity;
                //면 뒷(윗)면 색
                half4 topColor = _TopColor + backfoam;
                //topColor.rgb += rim * _RimColor * _RimIntensity;
                //자르기 alpha clip
                clip(cutoffTop-0.01);

                return facing > 0 ? finalResult : topColor;
            }
            ENDHLSL
        }
    }
}