Unity中Shader裁剪空间推导（在Shader中使用）

文章目录 前言一、在Shader中使用转化矩阵1、在顶点着色器中定义转化矩阵2、用 UNITY_NEAR_CLIP_VALUE 区分平台矩阵3、定义一个枚举用于区分当前是处于什么相机 二、我们在DirectX平台下，看看效果1、正交相机下2、透视相机下3、最终代码

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前言

在上一篇文章中，我们推导得出了 透视相机到裁剪空间的转化矩阵

Unity中Shader裁剪空间推导（透视相机到裁剪空间的转化矩阵）

我们在正交矩阵Shader的基础上，继续测试

Unity中Shader裁剪空间推导（在Shader中实现）

在这篇文章中，我们在Shader中使用该矩阵测试一下。

OpenGL [ 2 n w 0 0 0 0 2 n h 0 0 0 0 n + f n − f 2 n f n − f 0 0 − 1 0 ] \begin{bmatrix} \frac{2n}{w} & 0 & 0 & 0 \\ 0 & \frac{2n}{h} & 0 &0\\ 0 & 0 & \frac{n+f}{n-f} &\frac{2nf}{n-f}\\ 0 & 0 & -1 & 0\\ \end{bmatrix} ​w2n​000​0h2n​00​00n−fn+f​−1​00n−f2nf​0​ ​DirectX [ 2 n w 0 0 0 0 2 n h 0 0 0 0 n f − n n f f − n 0 0 − 1 0 ] \begin{bmatrix} \frac{2n}{w} & 0 & 0 & 0 \\ 0 & \frac{2n}{h} & 0 &0\\ 0 & 0 & \frac{n}{f-n} &\frac{nf}{f-n}\\ 0 & 0 & -1 & 0\\ \end{bmatrix} ​w2n​000​0h2n​00​00f−nn​−1​00f−nnf​0​ ​

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一、在Shader中使用转化矩阵 1、在顶点着色器中定义转化矩阵 OpenGL：

M_clipP = float4x4 ( 2n/w,0,0,0, 0,2n/h,0,0, 0,0,(n+f)/(n-f),(2nf)/(n-f), 0,0,-1,0 );

DirectX：

M_clipP = float4x4 ( 2n/w,0,0,0, 0,2n/h,0,0, 0,0,n/(f-n),(n*f)/(f-n), 0,0,-1,0 );

2、用 UNITY_NEAR_CLIP_VALUE 区分平台矩阵 1为OpenGL-1为DirectX 3、定义一个枚举用于区分当前是处于什么相机

[Enum(OrthoGraphic,0,Perspective,1)]_CameraType(“CameraType”,Float) = 0

在手动转化矩阵时使用三目运算符来决定使用哪一个矩阵

float4x4 M_clip = _CameraType ? M_clipP : M_clipO; o.vertexCS = mul(M_clip,float4(vertexVS,1));

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二、我们在DirectX平台下，看看效果 1、正交相机下

2、透视相机下

3、最终代码 //平移变换 //缩放变换 //旋转变换（四维） //视图空间矩阵 //正交相机视图空间 -> 裁剪空间 Shader "MyShader/URP/P3_7_6" { Properties { [Header(MainTexx)] _MainTex("MainTex",2D) = "white"{} [Header(Transtion)] _Translate("Translate(XYZ)",Vector) = (0,0,0,0) _Scale("Scale(XYZ)",Vector)= (1,1,1,1) _Rotation("Rotation(XYZ)",Vector) = (0,0,0,0) [Header(View)] _ViewPos("View Pos",vector) = (0,0,0,0) _ViewTarget("View Target",vector) = (0,0,0,0) [Header(Camera)] _CameraParams("Size(X),Near(Y),Far(Z) Ratio(W)",Vector) = (0,0,0,1.777) [Enum(OrthoGraphic,0,Perspective,1)]_CameraType("CameraType",Float) = 0 } SubShader { Tags { "PenderPipeline"="UniversalPipeline" "RenderType"="Opaque" "Queue"="Geometry" } Pass { 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/Core.hlsl" #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Lighting.hlsl" struct Attribute { float4 vertexOS : POSITION; float2 uv : TEXCOORD0; }; struct Varying { float4 vertexCS : SV_POSITION; float2 uv : TEXCOORD0; }; CBUFFER_START(UnityPerMaterial) float4 _Translate; float4 _Scale; float4 _Rotation; float4 _ViewPos; float4 _ViewTarget; float4 _CameraParams; float _CameraType; CBUFFER_END TEXTURE2D(_MainTex); SAMPLER(sampler_MainTex); Varying vert (Attribute v) { Varying o; o.uv = v.uv; //平移变换 float4x4 M_Translate = float4x4 ( 1,0,0,_Translate.x, 0,1,0,_Translate.y, 0,0,1,_Translate.z, 0,0,0,1 ); v.vertexOS = mul(M_Translate,v.vertexOS); //缩放交换 float4x4 M_Scale = float4x4 ( _Scale.x,0,0,0, 0,_Scale.y,0,0, 0,0,_Scale.z,0, 0,0,0,1 ); v.vertexOS = mul(M_Scale,v.vertexOS); //旋转变换 float4x4 M_rotateX = float4x4 ( 1,0,0,0, 0,cos(_Rotation.x),sin(_Rotation.x),0, 0,-sin(_Rotation.x),cos(_Rotation.x),0, 0,0,0,1 ); float4x4 M_rotateY = float4x4 ( cos(_Rotation.y),0,sin(_Rotation.y),0, 0,1,0,0, -sin(_Rotation.y),0,cos(_Rotation.y),0, 0,0,0,1 ); float4x4 M_rotateZ = float4x4 ( cos(_Rotation.z),sin(_Rotation.z),0,0, -sin(_Rotation.z),cos(_Rotation.z),0,0, 0,0,1,0, 0,0,0,1 ); v.vertexOS = mul(M_rotateX,v.vertexOS); v.vertexOS = mul(M_rotateY,v.vertexOS); v.vertexOS = mul(M_rotateZ,v.vertexOS); //观察空间矩阵推导 //P_view = [W_view] * P_world //P_view = [V_world]^-1 * P_world //P_view = [V_world]^T * P_world float3 ViewZ = normalize(_ViewPos.xyz - _ViewTarget.xyz); float3 ViewY = float3(0,1,0); float3 ViewX = cross(ViewZ,ViewY); ViewY = cross(ViewX,ViewZ); float4x4 M_viewTemp = float4x4 ( ViewX.x,ViewX.y,ViewX.z,0, ViewY.x,ViewY.y,ViewY.z,0, ViewZ.x,ViewZ.y,ViewZ.z,0, 0,0,0,1 ); float4x4 M_viewTranslate = float4x4 ( 1,0,0,-_ViewPos.x, 0,1,0,-_ViewPos.y, 0,0,1,-_ViewPos.z, 0,0,0,1 ); float4x4 M_view = mul(M_viewTemp,M_viewTranslate); float3 vertexWS = TransformObjectToWorld(v.vertexOS.xyz); //世界空间转化到观察空间 float3 vertexVS = mul(M_view,float4(vertexWS,1)).xyz; //相机参数 float h = _CameraParams.x * 2; float w = h * _CameraParams.w; float n = _CameraParams.y; float f = _CameraParams.z; //正交相机投影矩阵 //P_Clip = [M_Clip] * P_view float4x4 M_clipO; if(UNITY_NEAR_CLIP_VALUE==-1) { //OpenGL M_clipO = float4x4 ( 2/w,0,0,0, 0,2/h,0,0, 0,0,2/(n - f),(n + f) / (n - f), 0,0,0,1 ); } if(UNITY_NEAR_CLIP_VALUE==1) { //DirectX M_clipO = float4x4 ( 2/w,0,0,0, 0,2/h,0,0, 0,0,1/(f-n),f/(f-n), 0,0,0,1 ); } //透视相机投影矩阵 float4x4 M_clipP; if(UNITY_NEAR_CLIP_VALUE==-1) { //OpenGL M_clipP = float4x4 ( 2*n/w,0,0,0, 0,2*n/h,0,0, 0,0,(n+f)/(n-f),(2*n*f)/(n-f), 0,0,-1,0 ); } if(UNITY_NEAR_CLIP_VALUE==1) { //DirectX M_clipP = float4x4 ( 2*n/w,0,0,0, 0,2*n/h,0,0, 0,0,n/(f-n),(n*f)/(f-n), 0,0,-1,0 ); } //手动将观察空间下的坐标转换到裁剪空间下 float4x4 M_clip = _CameraType ? M_clipP : M_clipO; o.vertexCS = mul(M_clip,float4(vertexVS,1)); //观察空间 转化到 齐次裁剪空间 //o.vertexCS = TransformWViewToHClip(vertexVS); //o.vertexCS = TransformObjectToHClip(v.vertexOS.xyz); return o; } half4 frag (Varying i) : SV_Target { float4 mainTex = SAMPLE_TEXTURE2D(_MainTex,sampler_MainTex,i.uv); return mainTex; } ENDHLSL } } }