Unity中Shader URP最简Shader框架（ShaderGraph 转 URP Shader）

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前言

在之前的文章中，我们学习了 ShaderLab 中 BuildIn Render Pipeline 下的Shader书写。在这篇文章中，我们来了解一下 URP 下 的最简Shader怎么编写。

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一、 我们先了解一下 Shader Graph 怎么操作

1、了解一下 Shader Graph 的面板信息

2、修改Shader路径

3、鼠标中键 或 Alt + 鼠标左键 移动画布

4、鼠标右键 打开创建节点菜单

5、把ShaderGraph节点转化为 Shader 代码

• 可以直接 查看 或 复制 编译后的Shader
  

6、可以看出 URP 和 BuildIn RP 大体框架一致

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二、把ShaderGraph转化后的 Shader 只保留最基础的通用前向渲染Pass

因为是由ShaderGraph转化过来的。所以，这里虽然简化了。但是，还是过于臃肿，在之后的文章中，我们来优化一下

Shader "MyShader/P2_10"
{
    Properties {}
    SubShader
    {
        Tags
        {
            "RenderPipeline"="UniversalPipeline"
            "RenderType"="Opaque"
            "Queue"="Geometry"
        }
        Pass
        {
            Name "Universal Forward"
            Tags
            {
                // LightMode: <None>
            }

            // Render State
            Cull Back
            Blend One Zero
            ZTest LEqual
            ZWrite On

            // Debug
            // <None>

            // --------------------------------------------------
            // Pass

            HLSLPROGRAM
            // Pragmas
            #pragma target 2.0
            #pragma multi_compile_instancing
            #pragma multi_compile_fog
            #pragma instancing_options renderinglayer
            #pragma vertex vert
            #pragma fragment frag

            // Keywords
            #pragma multi_compile _ LIGHTMAP_ON
            #pragma multi_compile _ DIRLIGHTMAP_COMBINED
            #pragma shader_feature _ _SAMPLE_GI
            #pragma multi_compile_fragment _ _DBUFFER_MRT1 _DBUFFER_MRT2 _DBUFFER_MRT3
            #pragma multi_compile_fragment _ DEBUG_DISPLAY
            #pragma multi_compile_fragment _ _SCREEN_SPACE_OCCLUSION
            // GraphKeywords: <None>

            // Defines

            #define ATTRIBUTES_NEED_NORMAL
            #define ATTRIBUTES_NEED_TANGENT
            #define VARYINGS_NEED_POSITION_WS
            #define VARYINGS_NEED_NORMAL_WS
            #define FEATURES_GRAPH_VERTEX
            /* WARNING: $splice Could not find named fragment 'PassInstancing' */
            #define SHADERPASS SHADERPASS_UNLIT
            #define _FOG_FRAGMENT 1
            /* WARNING: $splice Could not find named fragment 'DotsInstancingVars' */


            // custom interpolator pre-include
            /* WARNING: $splice Could not find named fragment 'sgci_CustomInterpolatorPreInclude' */

            // Includes
            #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Color.hlsl"
            #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Texture.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Lighting.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Input.hlsl"
            #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/TextureStack.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/ShaderGraphFunctions.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/DBuffer.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/Editor/ShaderGraph/Includes/ShaderPass.hlsl"

            // --------------------------------------------------
            // Structs and Packing

            // custom interpolators pre packing
            /* WARNING: $splice Could not find named fragment 'CustomInterpolatorPrePacking' */

            struct Attributes
            {
                float3 positionOS : POSITION;
                float3 normalOS : NORMAL;
                float4 tangentOS : TANGENT;
                #if UNITY_ANY_INSTANCING_ENABLED
             uint instanceID : INSTANCEID_SEMANTIC;
                #endif
            };

            struct Varyings
            {
                float4 positionCS : SV_POSITION;
                float3 positionWS;
                float3 normalWS;
                #if UNITY_ANY_INSTANCING_ENABLED
             uint instanceID : CUSTOM_INSTANCE_ID;
                #endif
                #if (defined(UNITY_STEREO_MULTIVIEW_ENABLED)) || (defined(UNITY_STEREO_INSTANCING_ENABLED) && (defined(SHADER_API_GLES3) || defined(SHADER_API_GLCORE)))
             uint stereoTargetEyeIndexAsBlendIdx0 : BLENDINDICES0;
                #endif
                #if (defined(UNITY_STEREO_INSTANCING_ENABLED))
             uint stereoTargetEyeIndexAsRTArrayIdx : SV_RenderTargetArrayIndex;
                #endif
                #if defined(SHADER_STAGE_FRAGMENT) && defined(VARYINGS_NEED_CULLFACE)
             FRONT_FACE_TYPE cullFace : FRONT_FACE_SEMANTIC;
                #endif
            };

            struct SurfaceDescriptionInputs
            {
            };

            struct VertexDescriptionInputs
            {
                float3 ObjectSpaceNormal;
                float3 ObjectSpaceTangent;
                float3 ObjectSpacePosition;
            };

            struct PackedVaryings
            {
                float4 positionCS : SV_POSITION;
                float3 positionWS : INTERP0;
                float3 normalWS : INTERP1;
                #if UNITY_ANY_INSTANCING_ENABLED
             uint instanceID : CUSTOM_INSTANCE_ID;
                #endif
                #if (defined(UNITY_STEREO_MULTIVIEW_ENABLED)) || (defined(UNITY_STEREO_INSTANCING_ENABLED) && (defined(SHADER_API_GLES3) || defined(SHADER_API_GLCORE)))
             uint stereoTargetEyeIndexAsBlendIdx0 : BLENDINDICES0;
                #endif
                #if (defined(UNITY_STEREO_INSTANCING_ENABLED))
             uint stereoTargetEyeIndexAsRTArrayIdx : SV_RenderTargetArrayIndex;
                #endif
                #if defined(SHADER_STAGE_FRAGMENT) && defined(VARYINGS_NEED_CULLFACE)
             FRONT_FACE_TYPE cullFace : FRONT_FACE_SEMANTIC;
                #endif
            };

            PackedVaryings PackVaryings(Varyings input)
            {
                PackedVaryings output;
                    ZERO_INITIALIZE(PackedVaryings, output);
                output.positionCS = input.positionCS;
                output.positionWS.xyz = input.positionWS;
                output.normalWS.xyz = input.normalWS;
                #if UNITY_ANY_INSTANCING_ENABLED
            output.instanceID = input.instanceID;
                #endif
                #if (defined(UNITY_STEREO_MULTIVIEW_ENABLED)) || (defined(UNITY_STEREO_INSTANCING_ENABLED) && (defined(SHADER_API_GLES3) || defined(SHADER_API_GLCORE)))
            output.stereoTargetEyeIndexAsBlendIdx0 = input.stereoTargetEyeIndexAsBlendIdx0;
                #endif
                #if (defined(UNITY_STEREO_INSTANCING_ENABLED))
            output.stereoTargetEyeIndexAsRTArrayIdx = input.stereoTargetEyeIndexAsRTArrayIdx;
                #endif
                #if defined(SHADER_STAGE_FRAGMENT) && defined(VARYINGS_NEED_CULLFACE)
            output.cullFace = input.cullFace;
                #endif
                return output;
            }

            Varyings UnpackVaryings(PackedVaryings input)
            {
                Varyings output;
                output.positionCS = input.positionCS;
                output.positionWS = input.positionWS.xyz;
                output.normalWS = input.normalWS.xyz;
                #if UNITY_ANY_INSTANCING_ENABLED
            output.instanceID = input.instanceID;
                #endif
                #if (defined(UNITY_STEREO_MULTIVIEW_ENABLED)) || (defined(UNITY_STEREO_INSTANCING_ENABLED) && (defined(SHADER_API_GLES3) || defined(SHADER_API_GLCORE)))
            output.stereoTargetEyeIndexAsBlendIdx0 = input.stereoTargetEyeIndexAsBlendIdx0;
                #endif
                #if (defined(UNITY_STEREO_INSTANCING_ENABLED))
            output.stereoTargetEyeIndexAsRTArrayIdx = input.stereoTargetEyeIndexAsRTArrayIdx;
                #endif
                #if defined(SHADER_STAGE_FRAGMENT) && defined(VARYINGS_NEED_CULLFACE)
            output.cullFace = input.cullFace;
                #endif
                return output;
            }


            // --------------------------------------------------
            // Graph

            // Graph Properties
            CBUFFER_START(UnityPerMaterial)
            CBUFFER_END


            // Object and Global properties

            // Graph Includes
            // GraphIncludes: <None>

            // -- Property used by ScenePickingPass
            #ifdef SCENEPICKINGPASS
        float4 _SelectionID;
            #endif

            // -- Properties used by SceneSelectionPass
            #ifdef SCENESELECTIONPASS
        int _ObjectId;
        int _PassValue;
            #endif

            // Graph Functions
            // GraphFunctions: <None>

            // Custom interpolators pre vertex
            /* WARNING: $splice Could not find named fragment 'CustomInterpolatorPreVertex' */

            // Graph Vertex
            struct VertexDescription
            {
                float3 Position;
                float3 Normal;
                float3 Tangent;
            };

            VertexDescription VertexDescriptionFunction(VertexDescriptionInputs IN)
            {
                VertexDescription description = (VertexDescription)0;
                description.Position = IN.ObjectSpacePosition;
                description.Normal = IN.ObjectSpaceNormal;
                description.Tangent = IN.ObjectSpaceTangent;
                return description;
            }

            // Custom interpolators, pre surface
            #ifdef FEATURES_GRAPH_VERTEX
            Varyings CustomInterpolatorPassThroughFunc(inout Varyings output, VertexDescription input)
            {
                return output;
            }

            #define CUSTOMINTERPOLATOR_VARYPASSTHROUGH_FUNC
            #endif

            // Graph Pixel
            struct SurfaceDescription
            {
                float3 BaseColor;
            };

            SurfaceDescription SurfaceDescriptionFunction(SurfaceDescriptionInputs IN)
            {
                SurfaceDescription surface = (SurfaceDescription)0;
                surface.BaseColor = IsGammaSpace() ? float3(0.5, 0.5, 0.5) : SRGBToLinear(float3(0.5, 0.5, 0.5));
                return surface;
            }

            // --------------------------------------------------
            // Build Graph Inputs
            #ifdef HAVE_VFX_MODIFICATION
        #define VFX_SRP_ATTRIBUTES Attributes
        #define VFX_SRP_VARYINGS Varyings
        #define VFX_SRP_SURFACE_INPUTS SurfaceDescriptionInputs
            #endif
            VertexDescriptionInputs BuildVertexDescriptionInputs(Attributes input)
            {
                VertexDescriptionInputs output;
                ZERO_INITIALIZE(VertexDescriptionInputs, output);

                output.ObjectSpaceNormal = input.normalOS;
                output.ObjectSpaceTangent = input.tangentOS.xyz;
                output.ObjectSpacePosition = input.positionOS;

                return output;
            }

            SurfaceDescriptionInputs BuildSurfaceDescriptionInputs(Varyings input)
            {
                SurfaceDescriptionInputs output;
                ZERO_INITIALIZE(SurfaceDescriptionInputs, output);

                #ifdef HAVE_VFX_MODIFICATION
                #if VFX_USE_GRAPH_VALUES
            uint instanceActiveIndex = asuint(UNITY_ACCESS_INSTANCED_PROP(PerInstance, _InstanceActiveIndex));
            /* WARNING: $splice Could not find named fragment 'VFXLoadGraphValues' */
                #endif
                /* WARNING: $splice Could not find named fragment 'VFXSetFragInputs' */

                #endif


                #if UNITY_UV_STARTS_AT_TOP
                #else
                #endif


                #if defined(SHADER_STAGE_FRAGMENT) && defined(VARYINGS_NEED_CULLFACE)
        #define BUILD_SURFACE_DESCRIPTION_INPUTS_OUTPUT_FACESIGN output.FaceSign =                    IS_FRONT_VFACE(input.cullFace, true, false);
                #else
                #define BUILD_SURFACE_DESCRIPTION_INPUTS_OUTPUT_FACESIGN
                #endif
                #undef BUILD_SURFACE_DESCRIPTION_INPUTS_OUTPUT_FACESIGN

                return output;
            }

            // --------------------------------------------------
            // Main

            #include "Packages/com.unity.render-pipelines.universal/Editor/ShaderGraph/Includes/Varyings.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/Editor/ShaderGraph/Includes/UnlitPass.hlsl"

            // --------------------------------------------------
            // Visual Effect Vertex Invocations
            #ifdef HAVE_VFX_MODIFICATION
        #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/VisualEffectVertex.hlsl"
            #endif
            ENDHLSL
        }
    }

    FallBack "Hidden/Shader Graph/FallbackError"
}

1、我们看一下 URP Pass不可用后使用的默认Shader

使用的是内置渲染管线，返回颜色为洋葱紫

Shader "Hidden/Universal Render Pipeline/FallbackError"
{
    SubShader
    {
        Tags
        {
            "RenderType" = "Opaque"
            "RenderPipeline" = "UniversalPipeline"
            "IgnoreProjector" = "True"
        }

        Pass
        {
            HLSLPROGRAM
            #pragma target 2.0
            #pragma editor_sync_compilation

            // -------------------------------------
            // Shader Stages
            #pragma vertex vert
            #pragma fragment frag

            // -------------------------------------
            // Unity defined keywords
            #pragma multi_compile _ STEREO_INSTANCING_ON STEREO_MULTIVIEW_ON

            //--------------------------------------
            // GPU Instancing
            #include_with_pragmas "Packages/com.unity.render-pipelines.universal/ShaderLibrary/DOTS.hlsl"

            // -------------------------------------
            // Includes
            #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Common.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Input.hlsl"

            struct appdata_t
            {
                float4 vertex : POSITION;
                UNITY_VERTEX_INPUT_INSTANCE_ID
            };

            struct v2f
            {
                float4 vertex : SV_POSITION;
                UNITY_VERTEX_OUTPUT_STEREO
            };

            v2f vert (appdata_t v)
            {
                v2f o;
                UNITY_SETUP_INSTANCE_ID(v);
                UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(o);
                o.vertex = TransformObjectToHClip(v.vertex.xyz);
                return o;
            }

            float4 frag (v2f i) : SV_Target
            {
                return float4(1,0,1,1);
            }
            ENDHLSL
        }
    }

    Fallback "Hidden/Core/FallbackError"
}