在URP中实现平面透射阴影

博主： lazyun
发布时间：2022 年 05 月 21 日
932 次浏览
暂无评论
23956字数
分类：默认分类

#### 关于平面投射阴影，网上已经有很多文章介绍相关原理和优缺点：

- https://zhuanlan.zhihu.com/p/31504088
- https://zhuanlan.zhihu.com/p/266174847

这里记录一下在URP中的实现：

- 将URP Simple Lit Shader 源码拷贝新建一个Shader
- 修改成如下

```
// Shader targeted for low end devices. Single Pass Forward Rendering.
Shader "Custom/URP/Simple Lit"
{
    // Keep properties of StandardSpecular shader for upgrade reasons.
    Properties
    {
        [MainTexture] _BaseMap("Base Map (RGB) Smoothness / Alpha (A)", 2D) = "white" {}
        [MainColor] _BaseColor("Base Color", Color) = (1, 1, 1, 1)

_Cutoff("Alpha Clipping", Range(0.0, 1.0)) = 0.5

_Smoothness("Smoothness", Range(0.0, 1.0)) = 0.5
        _SpecColor("Specular Color", Color) = (0.5, 0.5, 0.5, 0.5)
        _SpecGlossMap("Specular Map", 2D) = "white" {}
        _SmoothnessSource("Smoothness Source", Float) = 0.0
        _SpecularHighlights("Specular Highlights", Float) = 1.0

[HideInInspector] _BumpScale("Scale", Float) = 1.0
        [NoScaleOffset] _BumpMap("Normal Map", 2D) = "bump" {}

[HDR] _EmissionColor("Emission Color", Color) = (0,0,0)
        [NoScaleOffset]_EmissionMap("Emission Map", 2D) = "white" {}

// Blending state
        _Surface("__surface", Float) = 0.0
        _Blend("__blend", Float) = 0.0
        _Cull("__cull", Float) = 2.0
        [ToggleUI] _AlphaClip("__clip", Float) = 0.0
        [HideInInspector] _SrcBlend("__src", Float) = 1.0
        [HideInInspector] _DstBlend("__dst", Float) = 0.0
        [HideInInspector] _ZWrite("__zw", Float) = 1.0

[ToggleUI] _ReceiveShadows("Receive Shadows", Float) = 1.0
        // Editmode props
        _QueueOffset("Queue offset", Float) = 0.0

// ObsoleteProperties
        [HideInInspector] _MainTex("BaseMap", 2D) = "white" {}
        [HideInInspector] _Color("Base Color", Color) = (1, 1, 1, 1)
        [HideInInspector] _Shininess("Smoothness", Float) = 0.0
        [HideInInspector] _GlossinessSource("GlossinessSource", Float) = 0.0
        [HideInInspector] _SpecSource("SpecularHighlights", Float) = 0.0

[HideInInspector][NoScaleOffset]unity_Lightmaps("unity_Lightmaps", 2DArray) = "" {}
        [HideInInspector][NoScaleOffset]unity_LightmapsInd("unity_LightmapsInd", 2DArray) = "" {}
        [HideInInspector][NoScaleOffset]unity_ShadowMasks("unity_ShadowMasks", 2DArray) = "" {}
    }

SubShader
    {
        Tags
        {
            "RenderType" = "Opaque" "RenderPipeline" = "UniversalPipeline" "UniversalMaterialType" = "SimpleLit" "IgnoreProjector" = "True" "ShaderModel"="4.5"
        }
        LOD 300

Pass
        {
            Name "PlanarShadowCaster"
            Tags
            {
                "RenderType"="Transparent"
                "Queue" = "Transparent"
                "RenderPipeline" = "Universal"
                "LightMode" = "SRPDefaultUnlit"
            }

//用使用模板测试以保证alpha显示正确
            Stencil
            {
                Ref 0
                Comp equal
                Pass incrWrap
                Fail keep
                ZFail keep
            }

//透明混合模式
//            Blend SrcAlpha OneMinusSrcAlpha
            Blend One Zero
            //关闭深度写入
            ZWrite off

//深度稍微偏移防止阴影与地面穿插
            Offset -1 , 0

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

HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag

struct appdata
            {
                float4 vertex : POSITION;
            };

struct v2f
            {
                float4 vertex : SV_POSITION;
                float4 color : COLOR;
            };

float _GroundLevel;
            // float4 _ShadowColor;
            // float _ShadowFalloff;

float3 ShadowProjectPos(float4 vertPos, Light mainLight)
            {
                float3 shadowPos;

//得到顶点的世界空间坐标
                float3 worldPos = TransformObjectToWorld(vertPos.xyz);

_GroundLevel = 0.5;
                //灯光方向
                float3 lightDir = normalize(mainLight.direction.xyz);

//阴影的世界空间坐标（低于地面的部分不做改变）
                shadowPos.y = min(worldPos.y, _GroundLevel);
                shadowPos.xz = worldPos.xz - lightDir.xz * max(0, worldPos.y - _GroundLevel) / lightDir.y;

return shadowPos;
            }

v2f vert(appdata v)
            {
                v2f o;
                Light mainLight = GetMainLight();

//得到阴影的世界空间坐标
                float3 shadowPos = ShadowProjectPos(v.vertex, mainLight);

//转换到裁切空间
                o.vertex = TransformWorldToHClip(shadowPos);

//得到中心点世界坐标
                float3 center = float3(unity_ObjectToWorld[0].w, _GroundLevel, unity_ObjectToWorld[2].w);
                //计算阴影衰减
                float falloff = 1 - saturate(distance(shadowPos, center) * 0.2);

//阴影颜色
                o.color = float4(0.18,.18,.18,1);
                o.color.a *= 1;

return o;
            }

half4 frag(v2f i) : SV_Target
            {
                return i.color;
            }
            ENDHLSL
        }

Pass
        {
            Name "ForwardLit"
            Tags
            {
                "LightMode" = "UniversalForward"
            }

// Use same blending / depth states as Standard shader
            Blend[_SrcBlend][_DstBlend]
            ZWrite On
            Cull[_Cull]

HLSLPROGRAM
            // #pragma exclude_renderers gles gles3 glcore
            // #pragma target 4.5

// -------------------------------------
            // Material Keywords
            #pragma shader_feature_local _NORMALMAP
            #pragma shader_feature_local_fragment _EMISSION
            #pragma shader_feature_local _RECEIVE_SHADOWS_OFF
            #pragma shader_feature_local_fragment _SURFACE_TYPE_TRANSPARENT
            #pragma shader_feature_local_fragment _ALPHATEST_ON
            #pragma shader_feature_local_fragment _ALPHAPREMULTIPLY_ON
            #pragma shader_feature_local_fragment _ _SPECGLOSSMAP _SPECULAR_COLOR
            #pragma shader_feature_local_fragment _GLOSSINESS_FROM_BASE_ALPHA

// -------------------------------------
            // Universal Pipeline keywords
            #pragma multi_compile _ _MAIN_LIGHT_SHADOWS _MAIN_LIGHT_SHADOWS_CASCADE _MAIN_LIGHT_SHADOWS_SCREEN
            #pragma multi_compile _ _ADDITIONAL_LIGHTS_VERTEX _ADDITIONAL_LIGHTS
            #pragma multi_compile _ LIGHTMAP_SHADOW_MIXING
            #pragma multi_compile _ SHADOWS_SHADOWMASK
            #pragma multi_compile_fragment _ _ADDITIONAL_LIGHT_SHADOWS
            #pragma multi_compile_fragment _ _SHADOWS_SOFT
            #pragma multi_compile_fragment _ _SCREEN_SPACE_OCCLUSION
            #pragma multi_compile_fragment _ _DBUFFER_MRT1 _DBUFFER_MRT2 _DBUFFER_MRT3
            #pragma multi_compile_fragment _ _LIGHT_LAYERS
            #pragma multi_compile_fragment _ _LIGHT_COOKIES
            #pragma multi_compile _ _CLUSTERED_RENDERING

//--------------------------------------
            // GPU Instancing
            #pragma multi_compile_instancing
            #pragma instancing_options renderinglayer
            #pragma multi_compile _ DOTS_INSTANCING_ON

#pragma vertex LitPassVertexSimple
            #pragma fragment LitPassFragmentSimple
            // #define BUMP_SCALE_NOT_SUPPORTED 1

#include "Packages/com.unity.render-pipelines.universal/Shaders/SimpleLitInput.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/Shaders/SimpleLitForwardPass.hlsl"
            ENDHLSL
        }

//        Pass
        //        {
        //            Name "ShadowCaster"
        //            Tags
        //            {
        //                "LightMode" = "ShadowCaster"
        //            }
        //
        //            ZWrite On
        //            ZTest LEqual
        //            ColorMask 0
        //            Cull[_Cull]
        //
        //            HLSLPROGRAM
        //            #pragma exclude_renderers gles gles3 glcore
        //            #pragma target 4.5
        //
        //            // -------------------------------------
        //            // Material Keywords
        //            #pragma shader_feature_local_fragment _ALPHATEST_ON
        //            #pragma shader_feature_local_fragment _GLOSSINESS_FROM_BASE_ALPHA
        //
        //            //--------------------------------------
        //            // GPU Instancing
        //            #pragma multi_compile_instancing
        //            #pragma multi_compile _ DOTS_INSTANCING_ON
        //
        //            // -------------------------------------
        //            // Universal Pipeline keywords
        //
        //            // This is used during shadow map generation to differentiate between directional and punctual light shadows, as they use different formulas to apply Normal Bias
        //            #pragma multi_compile_vertex _ _CASTING_PUNCTUAL_LIGHT_SHADOW
        //
        //            #pragma vertex ShadowPassVertex
        //            #pragma fragment ShadowPassFragment
        //
        //            #include "Packages/com.unity.render-pipelines.universal/Shaders/SimpleLitInput.hlsl"
        //            #include "Packages/com.unity.render-pipelines.universal/Shaders/ShadowCasterPass.hlsl"
        //            ENDHLSL
        //        }

Pass
        {
            Name "GBuffer"
            Tags
            {
                "LightMode" = "UniversalGBuffer"
            }

ZWrite[_ZWrite]
            ZTest LEqual
            Cull[_Cull]

HLSLPROGRAM
            #pragma exclude_renderers gles gles3 glcore
            #pragma target 4.5

// -------------------------------------
            // Material Keywords
            #pragma shader_feature_local_fragment _ALPHATEST_ON
            //#pragma shader_feature _ALPHAPREMULTIPLY_ON
            #pragma shader_feature_local_fragment _ _SPECGLOSSMAP _SPECULAR_COLOR
            #pragma shader_feature_local_fragment _GLOSSINESS_FROM_BASE_ALPHA
            #pragma shader_feature_local _NORMALMAP
            #pragma shader_feature_local_fragment _EMISSION
            #pragma shader_feature_local _RECEIVE_SHADOWS_OFF

// -------------------------------------
            // Unity defined keywords
            #pragma multi_compile _ DIRLIGHTMAP_COMBINED
            #pragma multi_compile _ LIGHTMAP_ON
            #pragma multi_compile _ DYNAMICLIGHTMAP_ON
            #pragma multi_compile _ LIGHTMAP_SHADOW_MIXING
            #pragma multi_compile _ SHADOWS_SHADOWMASK
            #pragma multi_compile_fragment _ _GBUFFER_NORMALS_OCT
            #pragma multi_compile_fragment _ _RENDER_PASS_ENABLED

#pragma vertex LitPassVertexSimple
            #pragma fragment LitPassFragmentSimple
            #define BUMP_SCALE_NOT_SUPPORTED 1

Pass
        {
            Name "DepthOnly"
            Tags
            {
                "LightMode" = "DepthOnly"
            }

ZWrite On
            ColorMask 0
            Cull[_Cull]

HLSLPROGRAM
            #pragma exclude_renderers gles gles3 glcore
            #pragma target 4.5

#pragma vertex DepthOnlyVertex
            #pragma fragment DepthOnlyFragment

// -------------------------------------
            // Material Keywords
            #pragma shader_feature_local_fragment _ALPHATEST_ON
            #pragma shader_feature_local_fragment _GLOSSINESS_FROM_BASE_ALPHA

//--------------------------------------
            // GPU Instancing
            #pragma multi_compile_instancing
            #pragma multi_compile _ DOTS_INSTANCING_ON

#include "Packages/com.unity.render-pipelines.universal/Shaders/SimpleLitInput.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/Shaders/DepthOnlyPass.hlsl"
            ENDHLSL
        }

//        // This pass is used when drawing to a _CameraNormalsTexture texture
        //        Pass
        //        {
        //            Name "DepthNormals"
        //            Tags
        //            {
        //                "LightMode" = "DepthNormals"
        //            }
        //
        //            ZWrite On
        //            Cull[_Cull]
        //
        //            HLSLPROGRAM
        //            #pragma exclude_renderers gles gles3 glcore
        //            #pragma target 4.5
        //
        //            #pragma vertex DepthNormalsVertex
        //            #pragma fragment DepthNormalsFragment
        //
        //            // -------------------------------------
        //            // Material Keywords
        //            #pragma shader_feature_local _NORMALMAP
        //            #pragma shader_feature_local_fragment _ALPHATEST_ON
        //            #pragma shader_feature_local_fragment _GLOSSINESS_FROM_BASE_ALPHA
        //
        //            //--------------------------------------
        //            // GPU Instancing
        //            #pragma multi_compile_instancing
        //            #pragma multi_compile _ DOTS_INSTANCING_ON
        //
        //            #include "Packages/com.unity.render-pipelines.universal/Shaders/SimpleLitInput.hlsl"
        //            #include "Packages/com.unity.render-pipelines.universal/Shaders/SimpleLitDepthNormalsPass.hlsl"
        //            ENDHLSL
        //        }

}

SubShader
    {
        Tags
        {
            "RenderType" = "Opaque" "RenderPipeline" = "UniversalPipeline" "UniversalMaterialType" = "SimpleLit" "IgnoreProjector" = "True" "ShaderModel"="2.0"
        }
        LOD 300

Pass
        {
            Name "ForwardLit"
            Tags
            {
                "LightMode" = "UniversalForward"
            }

// Use same blending / depth states as Standard shader
            Blend[_SrcBlend][_DstBlend]
            ZWrite On
            Cull[_Cull]

HLSLPROGRAM
            #pragma only_renderers gles gles3 glcore d3d11
            #pragma target 2.0

// -------------------------------------
            // Universal Pipeline keywords
            #pragma multi_compile _ _MAIN_LIGHT_SHADOWS _MAIN_LIGHT_SHADOWS_CASCADE _MAIN_LIGHT_SHADOWS_SCREEN
            #pragma multi_compile _ _ADDITIONAL_LIGHTS_VERTEX _ADDITIONAL_LIGHTS
            #pragma multi_compile _ LIGHTMAP_SHADOW_MIXING
            #pragma multi_compile _ SHADOWS_SHADOWMASK
            #pragma multi_compile_fragment _ _SHADOWS_SOFT
            #pragma multi_compile_fragment _ _ADDITIONAL_LIGHT_SHADOWS
            #pragma multi_compile_fragment _ _SCREEN_SPACE_OCCLUSION
            #pragma multi_compile_fragment _ _LIGHT_LAYERS
            #pragma multi_compile_fragment _ _LIGHT_COOKIES
            #pragma multi_compile _ _CLUSTERED_RENDERING

#pragma vertex LitPassVertexSimple
            #pragma fragment LitPassFragmentSimple
            #define BUMP_SCALE_NOT_SUPPORTED 1

Pass
        {
            Name "PlanarShadowCaster"
            Tags
            {
                "RenderType"="Opaque"
                "Queue" = "Opaque"
                "RenderPipeline" = "Universal"
                "LightMode" = "SRPDefaultUnlit"
            }

//透明混合模式
            Blend SrcAlpha OneMinusSrcAlpha

//关闭深度写入
            ZWrite off

//深度稍微偏移防止阴影与地面穿插
            Offset -1 , 0

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

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

HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag

struct appdata
            {
                float4 vertex : POSITION;
            };

struct v2f
            {
                float4 vertex : SV_POSITION;
                float4 color : COLOR;
            };

float _GroundLevel;
            float4 _ShadowColor;
            float _ShadowFalloff;

float3 ShadowProjectPos(float4 vertPos, Light mainLight)
            {
                float3 shadowPos;

//得到顶点的世界空间坐标
                float3 worldPos = TransformObjectToWorld(vertPos.xyz);

//灯光方向
                float3 lightDir = normalize(mainLight.direction.xyz);

return shadowPos;
            }

v2f vert(appdata v)
            {
                v2f o;
                Light mainLight = GetMainLight();

//得到阴影的世界空间坐标
                float3 shadowPos = ShadowProjectPos(v.vertex, mainLight);

//转换到裁切空间
                o.vertex = TransformWorldToHClip(shadowPos);

//阴影颜色
                o.color = _ShadowColor;
                o.color.a *= falloff;

return o;
            }

half4 frag(v2f i) : SV_Target
            {
                return i.color;
            }
            ENDHLSL
        }

//        Pass
        //        {
        //            Name "ShadowCaster"
        //            Tags
        //            {
        //                "LightMode" = "ShadowCaster"
        //            }
        //
        //            ZWrite On
        //            ZTest LEqual
        //            ColorMask 0
        //            Cull[_Cull]
        //
        //            HLSLPROGRAM
        //            #pragma only_renderers gles gles3 glcore d3d11
        //            #pragma target 2.0
        //
        //            // -------------------------------------
        //            // Material Keywords
        //            #pragma shader_feature_local_fragment _ALPHATEST_ON
        //            #pragma shader_feature_local_fragment _GLOSSINESS_FROM_BASE_ALPHA
        //
        //            // -------------------------------------
        //            // Universal Pipeline keywords
        //
        //            // This is used during shadow map generation to differentiate between directional and punctual light shadows, as they use different formulas to apply Normal Bias
        //            #pragma multi_compile_vertex _ _CASTING_PUNCTUAL_LIGHT_SHADOW
        //
        //            #pragma vertex ShadowPassVertex
        //            #pragma fragment ShadowPassFragment
        //
        //            #include "Packages/com.unity.render-pipelines.universal/Shaders/SimpleLitInput.hlsl"
        //            #include "Packages/com.unity.render-pipelines.universal/Shaders/ShadowCasterPass.hlsl"
        //            ENDHLSL
        //        }

Pass
        {
            Name "DepthOnly"
            Tags
            {
                "LightMode" = "DepthOnly"
            }

ZWrite On
            ColorMask 0
            Cull[_Cull]

HLSLPROGRAM
            #pragma only_renderers gles gles3 glcore d3d11
            #pragma target 2.0

#pragma vertex DepthOnlyVertex
            #pragma fragment DepthOnlyFragment

// Material Keywords
            #pragma shader_feature_local_fragment _ALPHATEST_ON
            #pragma shader_feature_local_fragment _GLOSSINESS_FROM_BASE_ALPHA

}
    Fallback "Hidden/Universal Render Pipeline/FallbackError"
    CustomEditor "UnityEditor.Rendering.Universal.ShaderGUI.SimpleLitShader"
}
```

最后修改：2022 年 05 月 21 日

发表评论取消回复
使用cookie技术保留您的个人信息以便您下次快速评论，继续评论表示您已同意该条款

在URP中实现平面透射阴影

lazyun • 2022 年 05 月 21 日