Shader "Custom/ParallaxCloud"
{
    Properties
    {
        _MainTex ("BaseMap：基础贴图", 2D) = "white" {}
//        _TurbulenceTex ("turbulence：扰动图", 2D) = "white" {}
        _Color ("Color：颜色", Color) = (0.0, 0.0, 0.0, 1.0)
        _ParallaxSize ("ParallaxSize：视差映射强度", Range(0.0, 0.1)) = 0.0
        _ParallaxLayers ("ParallaxLayers：视差映射层数", Range(1.0, 50.0)) = 20
        _MoveSpeed ("MoveSpeed：移动速度", Range(-0.5, 0.5)) = 0.1
        _Alpha ("Alpha：透明度", Range(0, 1)) = 0.5
        _AlphaExtent ("AlphaExtent：透明对比度", Range(0.0, 5.0)) = 5.0
//      _worldDis("云的最远距离", float) = 0
        _ruiHua("虚化距离", float) = 300
    }

    SubShader
    {
        Tags
        {
            "RenderPipeline"="UniversalPipeline"
            "Queue"="Transparent"
            "RenderType"="Transparent"
        }

        Pass
        {
            Blend SrcAlpha OneMinusSrcAlpha
            Cull off
            ZWrite off

            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Color.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Lighting.hlsl"

            struct Attributes
            {
                float4 positionOS : POSITION;
                float3 normalOS : NORMAL;
                float2 uv : TEXCOORD0;
                float4 tangent : TANGENT;
            };

            struct Varyings
            {
                float4 positionCS : SV_POSITION;
                float3 positionWS : TEXCOORD0;
                float4 uv : TEXCOORD1;
                float3 nDirWS : TEXCOORD2;
                float3 tDirWS : TEXCOORD3;
                float3 bDirWS : TEXCOORD4;
                float4 screenPos : TEXCOORD5;
            };

            CBUFFER_START(UnityPerMaterial)
                half4 _MainTex_ST;
                half4 _Color;
                half _ParallaxSize;
                half _ParallaxLayers;
                half _MoveSpeed;
                half _Alpha;
                half _AlphaExtent;
            // float _worldDis;
            float _ruiHua;
            CBUFFER_END

            TEXTURE2D(_MainTex);
            SAMPLER(sampler_MainTex);
            TEXTURE2D(_NormalTex);
            SAMPLER(sampler_NormalTex);
            TEXTURE2D(_ParallaxTex);
            SAMPLER(sampler_ParallaxTex);

            sampler2D _CameraDepthTexture;
            // TEXTURE2D(_TurbulenceTex);
            // SAMPLER(sampler_TurbulenceTex);

            Varyings vert(Attributes v)
            {
                Varyings o;
                o.positionCS = TransformObjectToHClip(v.positionOS.xyz);
                o.positionWS = TransformObjectToWorld(v.positionOS.xyz);
                o.nDirWS = TransformObjectToWorldNormal(v.normalOS);
                o.tDirWS = normalize(TransformObjectToWorld(v.tangent.xyz));
                o.bDirWS = normalize(cross(o.nDirWS, o.tDirWS) * v.tangent.w);
                
                // o.uv.xy = TRANSFORM_TEX(v.uv, _MainTex) + float2(frac(_Time.y * _MoveSpeed), 0.0);
                float2 newUV=o.positionWS.xz*0.06;
                o.uv.xy =TRANSFORM_TEX( newUV, _MainTex)  + float2(frac(_Time.y * _MoveSpeed), 0.0);
                o.uv.zw =  o.positionWS.xz * 0.02;
                o.screenPos = ComputeScreenPos(o.positionCS);
                return o;
            }

            // 从深度值重建世界坐标
            float3 ReconstructWorldPosition(float2 uv, float depth)
            {
                // 1. 将 UV 转换为 NDC 空间 (Normalized Device Coordinates)
                float4 ndc = float4(uv * 2.0 - 1.0, depth, 1.0);

                // 2. 从 NDC 转换到裁剪空间
                float4 clipPos = ndc;
                clipPos.z = depth * 2.0 - 1.0; // 将深度从 [0,1] 转换为 [-1,1]

                // 3. 应用逆投影矩阵，转换到视图空间
                float4 viewPos = mul(unity_CameraInvProjection, clipPos); // 使用 Unity 内置的逆投影矩阵
                viewPos /= viewPos.w; // 透视除法

                // 4. 应用逆视图矩阵，转换到世界空间
                float4 worldPos = mul(UNITY_MATRIX_I_V, viewPos); // 使用 Unity 内置的逆视图矩阵

                return worldPos.xyz;
            }

            half4 frag(Varyings i) : SV_Target
            {
                float2 positionSS = i.positionCS.xy * (_ScreenParams.zw - 1);
                float depth = tex2D(_CameraDepthTexture, positionSS).r;
                float3 positionNDC = float3(positionSS * 2 - 1, depth);

                #if UNITY_UV_STARTS_AT_TOP
                positionNDC.y = -positionNDC.y;
                #endif

                #if REQUIRE_POSITION_VS
        float4 positionVS = mul(UNITY_MATRIX_I_P, float4(positionNDC, 1));
        positionVS /= positionVS.w;
        float4 positionWS = mul(UNITY_MATRIX_I_V, positionVS);
                #else
                float4 positionWS = mul(UNITY_MATRIX_I_VP, float4(positionNDC, 1));
                positionWS /= positionWS.w;
                #endif
                float dist = length(positionWS - i.positionWS);
                // return half4(dist * 0.1, 0, 0, 1.0);
                dist = dist * 0.2;
                dist = clamp(dist, 0, 1);

                float ptcpos = length(i.positionWS - _WorldSpaceCameraPos);
                ptcpos = 1 - (ptcpos - 0) / _ruiHua;
                ptcpos = clamp(ptcpos, 0, 1);
                //Light mylight = GetMainLight();
                //half3 light = mylight.color;
                float3x3 TBN = float3x3(i.tDirWS, i.bDirWS, i.nDirWS);
                float3 vDir = normalize(i.positionWS - _WorldSpaceCameraPos.xyz);
                float3 vDirTS = mul(TBN, vDir);
                // float2 raoDongUv = SAMPLE_TEXTURE2D(_TurbulenceTex, sampler_TurbulenceTex,i.positionWS.xz * 0.06).r*0.1;
                // i.uv.xy += raoDongUv;
                // i.uv.zw += raoDongUv;
                float3 var_MainTex = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, i.uv.zw).rgb;


                half2 offset = 0.0;
                half currentDepth = 0.0;
                half parallaxDepth = 0.0;
                half preParallaxDepth = 0.0;
                half heightStep = 1.0 / _ParallaxLayers;
                half2 offsetTemp = vDirTS.xy / -vDirTS.z * _ParallaxSize;
                for (int j = 0; j < _ParallaxLayers; j++)
                {
                    parallaxDepth = 1.0 - SAMPLE_TEXTURE2D_LOD(_MainTex, sampler_MainTex, i.uv.xy + offset, 0).r *
                        var_MainTex.r;
                    if (currentDepth > parallaxDepth) break;
                    preParallaxDepth = parallaxDepth;
                    currentDepth += heightStep;
                    offset = offsetTemp * currentDepth;
                }
                half preDepth = currentDepth - heightStep;
                half A_C = preDepth - preParallaxDepth;
                half D_B = parallaxDepth - currentDepth;
                half t = A_C / (D_B + A_C);
                half height = lerp(preDepth, currentDepth, t);
                offset += offsetTemp * height;
                i.uv.xy += offset;

                half3 finalColor = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, i.uv.xy).rgb * var_MainTex.rgb;
                float alphaTex = max(var_MainTex.r * finalColor.r, 0.0);
                half alpha = max(pow(abs(lerp(alphaTex, 1.0, _Alpha)), _AlphaExtent), 0.0) * _Alpha * dist * ptcpos;
                return half4(finalColor * _Color.rgb, alpha);
            }
            ENDHLSL
        }
    }
}