从原理到实践，手把手教你开发冰Shader（一）

Shader "Unlit/Ice"{    Properties    {            }
    SubShader    {        Tags {"RenderType" = "Opaque" "RenderPipeline" = "UniversalPipeline" "Queue"="Geometry"}
        Pass        {            Name "Unlit"
            HLSLPROGRAM            #pragma exclude_renderers gles gles3 glcore            #pragma target 4.5                        // -------------------------------------
            #pragma vertex UnlitPassVertex            #pragma fragment UnlitPassFragment
            #include "IceInput.hlsl"            #include "IceForwardPass.hlsl"            ENDHLSL        }    }}

#include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/SurfaceInput.hlsl"
CBUFFER_START(UnityPerMaterial)
CBUFFER_END

struct Attributes{    float4 positionOS : POSITION;};
struct Varyings{    float4 positionCS  : SV_POSITION;};
Varyings UnlitPassVertex(Attributes input){    Varyings output = (Varyings)0;    VertexPositionInputs vertexInput = GetVertexPositionInputs(input.positionOS.xyz);    output.positionCS = vertexInput.positionCS;    return output;}
half4 UnlitPassFragment(Varyings input) : SV_Target{    return half4(1,1,1,1);}

struct IceInputData{};
void InitializeIceData(Varyings input, out IceInputData inputData){    inputData = (IceInputData)0;}

struct Attributes{    float4 positionOS : POSITION;};
struct Varyings{    float4 positionCS  : SV_POSITION;};
#include "IceFn.hlsl"

float3 positionWS = mul(UNITY_MATRIX_M, float4(positionOS, 1)).xyz;

float3 normalVS = mul(UNITY_MATRIX_IT_MV, float4(normalOS, 0)).xyz;//或者更简单的写法float3 normalVS = mul((float3x3)UNITY_MATRIX_IT_MV, normalOS);

struct IceInputData{    // 当前相机的世界空间位置    float3 cameraPosition;    // 模型表面着色点的世界空间位置    float3 positionWS;    // 世界空间的视觉方向，模型着色点指向相机的方向    float3 viewDirectionWS;    // 切线空间的视觉方向，是viewDirectionWS的不同空间描述    float3 viewDirectionTS;    // 世界空间的顶点法线方向    float3 vertexNormalWS;    // 世界空间的像素法线方向（包含法线贴图信息）    float3 pixelNormalWS;    // 切线空间的法线方向    float3 normalTS;    // 系统的运行时间    float time;};

half3 BlendAngleCorrectedNormals(half3 baseNormal, half3 additionalNormal){    baseNormal.b += 1.0;    additionalNormal.rg *= -1.0;    half d = dot(baseNormal, additionalNormal);    half3 tempBase = baseNormal * d;    half3 tempAdd = additionalNormal * baseNormal.b;    return tempBase - tempAdd;}
void EffectNormal(float3x3 t2w, float2 uv, out half3 normalTS, out half3 normalWS){    normalTS = half3(0, 0, 1);        #ifdef _USEGLASSNORMAL        normalTS = UnpackNormal(tex2D(_GlassNormal, uv));    normalTS.rg *= _GlassNormalScale;    normalTS = normalize(normalTS);        #ifdef _USEDETAILNORMAL    half3 detailNormalTS = UnpackNormal(tex2D(_DetailNormal, uv * _GlassDetailUVScale));    normalTS = BlendAngleCorrectedNormals(normalTS, detailNormalTS);    normalTS = normalize(normalTS);    #endif // _USEDETAILNORMAL        #endif // _USEGLASSNORMAL        normalWS = TransformTangentToWorld(normalTS, t2w);}
void InitializeIceData(Varyings input, out IceInputData inputData){    inputData = (IceInputData)0;        // 切线空间到世界空间的转换矩阵，由于每个顶点的切线坐标不一样，因此无法通过Unity统一传递过来，需要每个顶点去计算    float3x3 t2w = float3x3(input.tangentWS.xyz, input.bitangentWS.xyz, input.normalWS.xyz);        inputData.cameraPosition = GetCameraPositionWS();    inputData.positionWS = input.positionWS;    // 在顶点着色器已经计算出来并储存在相关通道上    inputData.viewDirectionWS = normalize(float3(input.normalWS.w, input.tangentWS.w, input.bitangentWS.w));    inputData.viewDirectionTS = TransformWorldToTangent(inputData.viewDirectionWS, t2w);    inputData.vertexNormalWS = normalize(input.normalWS.xyz);    EffectNormal(t2w, input.uv0.zw, inputData.normalTS, inputData.pixelNormalWS);    // _Time是Unity传递过来的时间参数，x:t/20 y:t z:t*2 w:t*3    inputData.time = _Time.x;}