Shader "NLD_URP/NLD_Scene_Grass"
{
    Properties
    {
        [MainTexture]_BaseMap ("主贴图", 2D) = "white" {}
        [MainColor] _BaseColor("基础颜色", Color) = (1, 1, 1, 1)
        _Cutoff("Alpha裁剪", Range(0.0, 1.0)) = 0.5
        
        _GroundColorTex ("地面颜色贴图", 2D) = "white" {}
        _GroundSize("地面大小(宽,高,融合高度)", Vector) = (50, 50, 0, 0)
        
        _WindNoiseTex ("风噪声贴图", 2D) = "white" {}
        _WindParams("风参数(XUV,YUV,摆动min,摆动max)", Vector) = (0.1, 0.1, 0, 0)
        _WindDirection("风向(风向xyz,风贴图强度缩放)", Vector) = (1, 0, 0, 0)
        
        _TimeScale("自然摆动时间缩放", Range(0, 1)) = 1
        
        _WindColor("风颜色", Color) = (1, 1, 1, 1)
        _WindColorParams("风颜色参数(压亮,截取min,截取max)", Vector) = (0.8, 0.2, 1, 0)
        
        _ShadowIntensity("阴影强度", Range(0, 1)) = 1
    }
    SubShader
    {
        Tags {
            "RenderType"="Transparent"
            "RenderPipeline" = "UniversalPipeline"
        }
        LOD 100
        
        HLSLINCLUDE

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

        TEXTURE2D(_BaseMap);
        SAMPLER(sampler_BaseMap);

        TEXTURE2D(_GroundColorTex);
        SAMPLER(sampler_GroundColorTex);

        sampler2D _WindNoiseTex;
        // TEXTURE2D(_WindNoiseTex);
        // SAMPLER(sampler_WindNoiseTex);

        struct Attributes_LT {
            float4 positionOS : POSITION;
            float2 uv : TEXCOORD0;

            UNITY_VERTEX_INPUT_INSTANCE_ID
        };

        struct Varyings_LT {
            float4 positionCS : SV_POSITION;
            // UV
            float2 uv : TEXCOORD0;
            // world position
            float3 worldPos : TEXCOORD1;
            float windNoise : TEXCOORD2;
            
            UNITY_VERTEX_INPUT_INSTANCE_ID
            UNITY_VERTEX_OUTPUT_STEREO
        };

        #if !defined(UNITY_INSTANCING_ENABLED)
        CBUFFER_START(UnityPerMaterial)
        #endif
            float _Cutoff;
            float4 _BaseColor;
            float4 _GroundSize;
            float4 _WindParams;
            float4 _WindDirection;

            float _TimeScale;

            float4 _BaseMap_ST;
            float4 _GroundColorTex_ST;
            float4 _WindNoiseTex_ST;
            float4 _WindColor;
            float4 _WindColorParams;
            float _ShadowIntensity;
        #if !defined(UNITY_INSTANCING_ENABLED)
        CBUFFER_END
        #endif

        Varyings_LT Vert(Attributes_LT input)
        {
            Varyings_LT output;
            UNITY_SETUP_INSTANCE_ID(input);
            output.worldPos = TransformObjectToWorld(input.positionOS).xyz;

            // 采样风噪声
            float2 groundStartPos = -float2(_GroundSize.x, _GroundSize.y) * 0.5;
            float2 groundUV = (output.worldPos.xz - groundStartPos.xy) / _GroundSize.xy;
            float xUVMove = _Time.y * _WindParams.x;
            float yUVMove = _Time.y * _WindParams.y;
            float2 windUv = groundUV + float2(xUVMove, yUVMove);
            float2 windUvWrap = TRANSFORM_TEX(windUv, _WindNoiseTex);
            float windNoise = tex2Dlod(_WindNoiseTex, float4(windUvWrap, 0, 0)).r;
            float windMinY = _WindParams.z;
            float windMaxY = _WindParams.w;
            float lerpProgress = clamp((output.worldPos.y - windMinY) / (windMaxY - windMinY), 0, 10);
            // 根据风噪声做顶点偏移
            float3 moveDt = lerp(0, _WindDirection.xyz, lerpProgress) * sin((windNoise * _WindDirection.w + _TimeScale * _Time.y) * 2 * 3.14);
            output.worldPos = output.worldPos + moveDt;
            
            output.positionCS = TransformWorldToHClip(output.worldPos);
            output.uv = TRANSFORM_TEX(input.uv, _BaseMap);
            output.windNoise = windNoise;
            return output;
        }
        
        ENDHLSL

        Pass
        {
            Cull Off
            Name "ForwardLit"
            Tags {
                "LightMode" = "UniversalForward"
            }
            ZWrite On
            ZTest LEqual
            
            HLSLPROGRAM
            #pragma target 3.0
            #pragma vertex Vert
            #pragma fragment Frag
            // 开启instance
            #pragma multi_compile_instancing

            // 开启接收阴影
            #pragma multi_compile _ _MAIN_LIGHT_SHADOWS //主光源阴影
            #pragma multi_compile _ _SHADOWS_SOFT //软阴影

            float4 Frag(Varyings_LT input): SV_Target
            {
                // 基础色alpha clip
                float4 baseColor = SAMPLE_TEXTURE2D(_BaseMap, sampler_BaseMap, input.uv);
                if (baseColor.a < _Cutoff)
                    discard;

                // 根据worldPos计算地面颜色
                float2 groundStartPos = -float2(_GroundSize.x, _GroundSize.y) * 0.5;
                float2 groundUV = (input.worldPos.xz - groundStartPos.xy) / _GroundSize.xy;
                float4 groundColor = SAMPLE_TEXTURE2D(_GroundColorTex, sampler_GroundColorTex, groundUV);

                // 基础色
                float4 grassColor = _BaseColor;

                // 读取风噪声强度
                if (input.windNoise > _WindColorParams.y && input.windNoise < _WindColorParams.z)
                {
                    float scaleWindNoise = input.windNoise * _WindColorParams.x;
                    grassColor = lerp(grassColor, _WindColor, input.windNoise * scaleWindNoise);
                }

                // 根据高度做颜色混合
                float blendHeight = _GroundSize.z;
                float lerpProgress = clamp(input.worldPos.y / blendHeight, 0, 1);
                float4 lerpColor = lerp(groundColor, grassColor, lerpProgress);

                // 获取阴影
                float4 shadowCoord = TransformWorldToShadowCoord(input.worldPos);
                Light mainLight = GetMainLight(shadowCoord);
                // 读取shadowStrength
                float shadowStrength = lerp(1, mainLight.shadowAttenuation, _ShadowIntensity);
                lerpColor *= shadowStrength;

                return lerpColor;
            }
            ENDHLSL
        }

        Pass
        {
            Cull Off
            Name "ShadowCaster"
            Tags
            {
                "LightMode" = "ShadowCaster"
            }
            
            HLSLPROGRAM
            #pragma target 3.0
            #pragma vertex Vert
            #pragma fragment Frag
            // 开启instance
            #pragma multi_compile_instancing

            float4 Frag(Varyings_LT input): SV_Target
            {
                // 基础色alpha clip
                float4 baseColor = SAMPLE_TEXTURE2D(_BaseMap, sampler_BaseMap, input.uv);
                if (baseColor.a < _Cutoff)
                    discard;
                return float4(1, 1, 1, 1);
            }

            
            ENDHLSL
            
        }

    }
}