参考shaderx2 中DOF via Simulation of Circle of Confusion 算法 or http://amdstaging.wpengine.com/wordpress/media/2012/10/Scheuermann_DepthOfField.pdf，引擎中增加了depth of field 功能模块。基本原理就是根据物体与聚焦平面的距离来设定模糊kernel的大小，对远离聚焦平面的物体做模糊处理。
视频地址：
1.首先将场景中物体的颜色渲染到一个render target上，颜色计算公式可以自己定，以下是我用的方法：
output.Color = saturate( dot(input.Norm, normalize(SunLightDir)) * vLightColor + diffuse + vAmbiantColor );
2.再将场景深度，模糊值blur分别存到另一个render target的R值和G值
深度模糊值计算方法如下：
float blur = saturate(abs(input.Depth - focalDist) / focalRange);
input.Depth为物体深度，focalDist为聚焦平面的值，focalRange为聚焦范围，blue这样计算的话就在0-1范围内。
output.Depth = float4(depth, blur, 0, 1);
下面的话就是按照以上两个信息做模糊处理
首先建立一个屏幕大小的平面，有四个顶点，作为画布传入vertex shader
从第一个贴图中获取物体颜色
float4 colorSum = g_SceneTexture.Sample( g_samClamp, input.Tex );
然后从另一张贴图去除深度值和模糊值
float2 centerDepthBlur = g_DepthTexture.Sample( g_samClamp, input.Tex );
依据模糊值确定kernel大小
float sizeCoC = centerDepthBlur.y * g_MaxCoC;
下面是关键：
for (int i = 0; i < 12; i++)//kernel中原先有的12个采样点
{ // Compute tap coordinates float2 tapCoord = input.Tex + g_FilterTaps[i] * sizeCoC;计算采样点的纹理坐标 // Fetch tap sample float4 tapColor = g_SceneTexture.Sample(g_samClamp, tapCoord); 采样点所在位置的颜色值 float2 tapDepthBlur = g_DepthTexture.Sample(g_samClamp, tapCoord);采样点所在位置的深度和模糊因素// Compute tap contribution
float tapContribution = (tapDepthBlur.x > centerDepthBlur.x) ? 1.0f : tapDepthBlur.y;防止聚焦平面后面的物体采样到聚焦平面的物体的颜色值// Accumulate color and contribution
colorSum += tapColor * tapContribution; totalContribution += tapContribution; }// Normalize to get proper luminance
finalColor = colorSum / totalContribution;以下是截图，分别是没有DOF效果图，深度图，模糊因素图和有DOF的效果图
以下是所有shader代码
1 SamplerState g_samWrap 2 { 3 Filter = MIN_MAG_MIP_LINEAR; 4 AddressU = Wrap; 5 AddressV = Wrap; 6 }; 7 8 SamplerState g_samClamp 9 { 10 Filter = MIN_MAG_MIP_LINEAR; 11 AddressU = Clamp; 12 AddressV = Clamp; 13 }; 14 15 BlendState NoBlending 16 { 17 AlphaToCoverageEnable = FALSE; 18 BlendEnable[0] = FALSE; 19 }; 20 21 BlendState AlphaBlendingOn 22 { 23 BlendEnable[0] = TRUE; 24 SrcBlend = SRC_ALPHA; 25 DestBlend = INV_SRC_ALPHA; 26 }; 27 28 matrix World; 29 matrix View; 30 matrix Projection; 31 matrix LightView; 32 float3 SunLightDir; 33 34 float4 vLightColor = float4(0.3f, 0.3f, 0.3f, 1.0f); 35 float4 vAmbiantColor = float4(0.1f, 0.1f, 0.1f, 1.0f); 36 37 float focalDist = 1.0; 38 float focalRange = 1.0; 39 40 Texture2D g_SceneTexture; 41 Texture2D g_DepthTexture; 42 Texture2D g_ModelTexture; 43 44 float2 g_FilterTaps[12]; 45 46 float g_MaxCoC = 3; 47 48 struct VS_MODEL_INPUT 49 { 50 float4 Pos : POSITION; 51 float2 Tex : TEXCOORD0; 52 float3 Norm : NORMAL; 53 }; 54 55 struct PS_MODEL_INPUT 56 { 57 float4 Pos :SV_POSITION; 58 float2 Tex : TEXCOORD0; 59 float3 Norm : TEXCOORD1; 60 float Depth : TEXCOORD2; 61 }; 62 63 struct PS_MODEL_OUTPUT 64 { 65 float4 Color : SV_Target1; 66 float4 Depth : SV_Target0; 67 }; 68 69 struct VS_DOF_INPUT 70 { 71 float4 Pos : POSITION; 72 float2 Tex : TEXCOORD0; 73 }; 74 75 struct PS_DOF_INPUT 76 { 77 float4 Pos :SV_POSITION; 78 float2 Tex : TEXCOORD0; 79 }; 80 81 PS_MODEL_INPUT VS_SCENE(VS_MODEL_INPUT input) 82 { 83 PS_MODEL_INPUT output = (PS_MODEL_INPUT)0; 84 output.Pos = input.Pos; 85 output.Pos.w = 1; 86 87 output.Pos = mul( output.Pos, World ); 88 output.Pos = mul( output.Pos, View ); 89 output.Pos = mul( output.Pos, Projection ); 90 output.Depth = output.Pos.z; 91 output.Pos = output.Pos / output.Pos.w; 92 93 output.Norm = mul( input.Norm, World ); 94 output.Norm = normalize( output.Norm ); 95 96 output.Tex = input.Tex; 97 98 return output; 99 }100 101 PS_MODEL_OUTPUT PS_SCENE( PS_MODEL_INPUT input ) : SV_Target102 {103 PS_MODEL_OUTPUT output = (PS_MODEL_OUTPUT)0;104 105 float4 diffuse = g_ModelTexture.Sample( g_samClamp, input.Tex );106 output.Color = saturate( dot(input.Norm, normalize(SunLightDir)) * vLightColor + diffuse + vAmbiantColor );107 108 float blur = saturate(abs(input.Depth - focalDist) / focalRange);109 float depth = input.Pos.z;110 output.Depth = float4(depth, blur, 0, 1);111 112 return output;113 }114 115 PS_DOF_INPUT VS_DOF(VS_DOF_INPUT input)116 {117 PS_DOF_INPUT output = (PS_DOF_INPUT)0;118 output.Pos = input.Pos;119 120 output.Tex = float2( input.Tex.x, 1 - input.Tex.y );121 122 return output;123 }124 125 float4 PS_DOF(PS_DOF_INPUT input) : SV_Target126 {127 float4 finalColor = 0;128 129 float4 colorSum = g_SceneTexture.Sample( g_samClamp, input.Tex );130 131 float2 centerDepthBlur = g_DepthTexture.Sample( g_samClamp, input.Tex );132 133 //return centerDepthBlur.y;134 135 float sizeCoC = centerDepthBlur.y * g_MaxCoC;//blur * maxCoC136 137 //return sizeCoC;138 float totalContribution = 1.0f;139 140 for (int i = 0; i < 12; i++)141 {142 // Compute tap coordinates143 float2 tapCoord = input.Tex + g_FilterTaps[i] * sizeCoC;144 145 // Fetch tap sample146 float4 tapColor = g_SceneTexture.Sample(g_samClamp, tapCoord); 147 float2 tapDepthBlur = g_DepthTexture.Sample(g_samClamp, tapCoord);148 149 // Compute tap contribution150 //for obj in front, use tapDepthBlur.y, and if obj is in focus, tapDepthBlur.y is 0, so no leak of front obj color; for back obj, use 1.0f151 float tapContribution = (tapDepthBlur.x > centerDepthBlur.x) ? 1.0f : tapDepthBlur.y;152 153 // Accumulate color and contribution154 colorSum += tapColor * tapContribution;155 totalContribution += tapContribution;156 }157 158 // Normalize to get proper luminance159 finalColor = colorSum / totalContribution;160 161 return finalColor;162 }163 164 technique10 DoF165 {166 pass p0167 {168 SetVertexShader( CompileShader( vs_4_0, VS_SCENE() ) );169 SetGeometryShader( NULL );170 SetPixelShader( CompileShader( ps_4_0, PS_SCENE() ) );171 172 SetBlendState( NoBlending, float4( 0.0f, 0.0f, 0.0f, 0.0f ), 0xFFFFFFFF );173 } 174 175 pass p1176 {177 SetVertexShader( CompileShader( vs_4_0, VS_DOF() ) );178 SetGeometryShader( NULL );179 SetPixelShader( CompileShader( ps_4_0, PS_DOF() ) );180 181 SetBlendState( NoBlending, float4( 0.0f, 0.0f, 0.0f, 0.0f ), 0xFFFFFFFF );182 } 183 }