Directx10 龙书笔记- 雾效的实现

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雾：说白了就是一层有颜色的(一般是白色，灰色) 蒙蒙的感觉混在光线里面。不管是白天还是黑天。

龙书里面是这样实现的：

1. 给雾定义一个颜色 float3 gFogColor={0.7f,0.7f,0.7f};

2. 然后呢在顶点着色器里面计算出顶点级别的雾化需要的颜色加成比例

加成比例：意思是当距离摄像机，就是你的眼睛越远，雾的浓度越大，就是颜色越深。根据这个得出一个(0,1)的和距离有关的比例系数

vout.fogLerp = saturate((d-gFogStart)/gFogRange) ; 其中 gFogStart是可见范围，没有雾的范围，gFogRange是不可见范围，超出这个范围就全是雾

saturate是强制为(0,1)这个区间。

3. 在像素着色器像素级别的融合纹理颜色和雾的颜色

float3 floggedColor = lerp(litColor,gFogColor,pIn.fogLerp);

具体fx代码为:

//=============================================================================// fog.fx by Frank Luna (C) 2008 All Rights Reserved.//// Same as clip.fx, but adds fog in the vertex shader.// Note that we could do fog in the pixel shader, but if the scene// has sufficient triangle density, not much is gained. //=============================================================================#include "lighthelper.fx" cbuffer cbPerFrame{Light gLight;float3 gEyePosW;};cbuffer cbPerObject{float4x4 gWorld;float4x4 gWVP; float4x4 gTexMtx;};cbuffer cbFixed{// For this demo, we hardcode the fog values.  However, in a real// application, the program may want to change the fog settings// at runtime; for example, to fade the fog in and out based on // the time of day or the location of the game player. float  gFogStart = 5.0f;float  gFogRange = 140.0f;float3 gFogColor = {0.7f, 0.7f, 0.7f};};// Nonnumeric values cannot be added to a cbuffer.Texture2D gDiffuseMap;Texture2D gSpecMap;SamplerState gTriLinearSam{Filter = MIN_MAG_MIP_LINEAR;AddressU = Wrap;AddressV = Wrap;};struct VS_IN{float3 posL    : POSITION;float3 normalL : NORMAL;float2 texC    : TEXCOORD;};struct VS_OUT{float4 posH    : SV_POSITION;    float3 posW    : POSITION;    float3 normalW : NORMAL;    float2 texC0   : TEXCOORD0;    float2 texC1   : TEXCOORD1;    float  fogLerp : FOG;}; VS_OUT VS(VS_IN vIn){VS_OUT vOut;// Transform to world space space.vOut.posW    = mul(float4(vIn.posL, 1.0f), gWorld);vOut.normalW = mul(float4(vIn.normalL, 0.0f), gWorld);// Transform to homogeneous clip space.vOut.posH = mul(float4(vIn.posL, 1.0f), gWVP);// Output vertex attributes for interpolation across triangle.vOut.texC0  = vIn.texC;vOut.texC1  = mul(float4(vIn.texC, 0.0f, 1.0f), gTexMtx);float d      = distance(vOut.posW, gEyePosW);vOut.fogLerp = saturate( (d - gFogStart) / gFogRange ); return vOut;}float4 PS(VS_OUT pIn) : SV_Target{// Get materials from texture maps.float alpha    = gDiffuseMap.Sample( gTriLinearSam, pIn.texC0 ).a;// Discard pixel if texture alpha < 0.1.  Note that we do this// test as soon as possible so that we can potentially exit the shader // early, thereby skipping the rest of the shader code.clip(alpha - 0.1f);float4 diffuse = gDiffuseMap.Sample( gTriLinearSam, pIn.texC1 );float4 spec    = gSpecMap.Sample( gTriLinearSam, pIn.texC1 );// Map [0,1] --> [0,256]spec.a *= 256.0f;// Interpolating normal can make it not be of unit length so normalize it.    float3 normalW = normalize(pIn.normalW);    // Compute the lit color for this pixel.    SurfaceInfo v = {pIn.posW, normalW, diffuse, spec};float3 litColor = ParallelLight(v, gLight, gEyePosW);// Blend the fog color and the lit color.float3 foggedColor = lerp(litColor, gFogColor, pIn.fogLerp);    return float4(foggedColor, alpha);}technique10 FogTech{    pass P0    {        SetVertexShader( CompileShader( vs_4_0, VS() ) );        SetGeometryShader( NULL );        SetPixelShader( CompileShader( ps_4_0, PS() ) );    }}

因为这是笔记，详细代码就不贴了，龙书网站有

给个实现效果吧：

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