原链接 /myspace/item/f09e7c948170c04bf14215e2
Cg实现景深效果
景深其实就是对blur filter的一种改进，使其对每个像素的blur程度都有所不同，
而blur的依据就是场景的深度和当前焦距之间的关系。
1.渲染深度到纹理。
相关SHADER如下：
//AdaptDepthVS.cg
//取得顶点的深度值，并且插值到PS中去
uniform float4x4 modelViewProj : state.matrix.mvp;
uniform float farclip; //远裁剪面距离
void main(float4 inPos : POSITION,
out float4 oPos : POSITION,
out float oDepth : TEXCOORD0)
{
float4 OutPos;
oPos = OutPos = mul(modelViewProj, inPos);
oDepth = OutPos.w / farclip;
}
//AdaptDepthPs.cg
//将插值的深度转换成颜色
//白色越近，黑色越远。
void main(float4 inDepth : TEXCOORD0,
out float4 color : COLOR0)
{
float depthColor = inDepth.r;
color = float4(depthColor, depthColor, depthColor, 1.0);
}
以上代码讲深度转换成颜色，储存在纹理中，供景深的shader来查询。
2.景深shader
//DepthOfFieldPs.cg
//处理景深效果
uniform sampler2D depthTex; //深度图
uniform sampler2D sceneTex; //场景渲染图
uniform float nearclip; //近裁剪面
uniform float farclip; //远裁剪面
uniform float focus; //焦距
uniform float viewPortInvX; //视口宽度的倒数
uniform float viewPortInvY; //视口高度的倒数
void main(float2 texCoord : TEXCOORD0,
out float4 color : COLOR)
{
float4 Depthvalue = tex2D(depthTex, texCoord);
//计算出真实的深度
float realDepth = nearclip + Depthvalue.r*(farclip - nearclip);
//计算深度于焦距的差值
float dfocus = abs(realDepth - focus);
//计算出模糊因子,距离的平方成正比
float blurFactor = 1.0-pow(-dfocus/(farclip-nearclip), 2.0);
blurFactor*=2.5;
color = float4(0, 0, 0, 0);
color+=tex2D(sceneTex,texCoord + float2(-1.0*viewPortInvX*blurFactor ,-1.0*viewPortInvY*blurFactor)) * (1.0/16.0);
color+=tex2D(sceneTex,texCoord + float2(-1.0*viewPortInvX*blurFactor , 1.0*viewPortInvY*blurFactor)) * (1.0/16.0);
color+=tex2D(sceneTex,texCoord + float2( 1.0*viewPortInvX*blurFactor ,-1.0*viewPortInvY*blurFactor)) * (1.0/16.0);
color+=tex2D(sceneTex,texCoord + float2( 1.0*viewPortInvX*blurFactor , 1.0*viewPortInvY*blurFactor)) * (1.0/16.0);
color+=tex2D(sceneTex,texCoord + float2(-1.0*viewPortInvX*blurFactor , 0.0*viewPortInvY*blurFactor)) * (2.0/16.0);
color+=tex2D(sceneTex,texCoord + float2( 1.0*viewPortInvX*blurFactor , 0.0*viewPortInvY*blurFactor)) * (2.0/16.0);
color+=tex2D(sceneTex,texCoord + float2( 0.0*viewPortInvX*blurFactor ,-1.0*viewPortInvY*blurFactor)) * (2.0/16.0);
color+=tex2D(sceneTex,texCoord + float2( 0.0*viewPortInvX*blurFactor , 1.0*viewPortInvY*blurFactor)) * (2.0/16.0);
color+=tex2D(sceneTex,texCoord + float2( 0.0*viewPortInvX*blurFactor , 0.0*viewPortInvY*blurFactor)) * (4.0/16.0);
}
上面代码根据计算出来的blurFactor来做为blur程度的依据，
其算法是，当前像素的深度值与焦距的差值绝对值的平方 与 模糊程度成正比。
