HDRBloom（光晕）
取亮光部分，进行降采样，在升采样的过程中，叠加降采样对应尺寸的图片，合并效果图和源图片
初处理
如果放入的是HDR图片，可以在shader里面加float4 _MainTex_HDR; col.rgb = DecodeHDR(col,_MainTex_HDR);进行解码。
取光亮部分
先进行均值模糊，取亮色部分。
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| float intensity = Mathf.Exp(_Intensity / 10.0f * 0.693f) - 1.0f;
mat.SetFloat("_Threshold", _Threshold);
mat.SetFloat("_Intensity", intensity);
Graphics.Blit(source, RT_Down[0], mat, 0);
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| half4 frag_PreFilter(v2f_img i) : SV_Target
{
half4 col = tex2D(_MainTex, i.uv);
half4 d=_MainTex_TexelSize.xyxy*half4(1,1,-1,-1);
col.rgb+=tex2D(_MainTex,i.uv+d.xy).rgb;
col.rgb+=tex2D(_MainTex,i.uv+d.zy).rgb;
col.rgb+=tex2D(_MainTex,i.uv+d.xw).rgb;
col.rgb+=tex2D(_MainTex,i.uv+d.zw).rgb;
col.rgb*=0.25;
float br = max(max(col.r,col.g),col.b);
br = max(0,(br - _Threshold))/max(0.00001,br);
col.rgb*=br;
return col;
}
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降采样
用双重盒状模糊的降采样方式
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for(int i=0;i<_Iteration;i++) {
Graphics.Blit(RT_Down[i], RT_Down[i + 1], mat, 1);
}
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| half4 frag_DownsampleBox(v2f_img i) : SV_Target
{
half4 col = tex2D(_MainTex, i.uv);
half4 d=_MainTex_TexelSize.xyxy*half4(1,1,-1,-1);
col.rgb+=tex2D(_MainTex,i.uv+d.xy).rgb;
col.rgb+=tex2D(_MainTex,i.uv+d.zy).rgb;
col.rgb+=tex2D(_MainTex,i.uv+d.xw).rgb;
col.rgb+=tex2D(_MainTex,i.uv+d.zw).rgb;
col.rgb*=0.25;
return col;
}
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升采样
升采样过程中加同尺寸的降采样贴图
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| Graphics.Blit(RT_Down[_Iteration], RT_Up[_Iteration]);
for(int i=_Iteration;i>0;i--) {
mat.SetTexture("_BloomTex", RT_Down[i-1]);
Graphics.Blit(RT_Up[i], RT_Up[i-1], mat, 2);
}
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| half4 frag_UpsampleBox(v2f_img i) : SV_Target
{
half4 col = tex2D(_MainTex, i.uv);
half4 d=_MainTex_TexelSize.xyxy*half4(1,1,-1,-1);
col.rgb+=tex2D(_MainTex,i.uv+d.xy).rgb;
col.rgb+=tex2D(_MainTex,i.uv+d.zy).rgb;
col.rgb+=tex2D(_MainTex,i.uv+d.xw).rgb;
col.rgb+=tex2D(_MainTex,i.uv+d.zw).rgb;
col.rgb*=0.25;
half4 color2 = tex2D(_BloomTex, i.uv);
return col + color2;
}
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合并
把升采样的最后一张图和原图合并,和释放贴图。
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| mat.SetTexture("_BloomTex", RT_Up[0]);
Graphics.Blit(source, destination, mat, 3);
for (int i = 0; i < _Iteration+1; i++) {
RenderTexture.ReleaseTemporary(RT_Down[i]);
RenderTexture.ReleaseTemporary(RT_Up[i]);
}
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| half4 frag_Combine(v2f_img i) : SV_Target
{
half4 col = tex2D(_MainTex, i.uv);
half3 color1 = tex2D(_BloomTex, i.uv).rgb;
col.rgb+= color1.rgb*_Intensity;
return col ;
}
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最后小瑕疵
在光晕的周围还有点不自然。可用如下解决方案。
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| float3 ACES_Tonemapping(float3 x)
{
float a = 2.51f;
float b = 0.03f;
float c = 2.43f;
float d = 0.59f;
float e = 0.14f;
float3 encode_color = saturate((x*(a*x + b)) / (x*(c*x + d) + e));
return encode_color;
};
half4 frag (v2f_img i) : SV_Target
{
half4 col = tex2D(_MainTex, i.uv);
half3 linear_color = pow(col.rgb, 2.2);
half3 encode_color = ACES_Tonemapping(linear_color);
half3 final_color = pow(encode_color, 1.0 / 2.2);
return float4(final_color,col.a);
}
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后处理的顺序
调整顺序：Bloom->Vignette->Tonemapping->ColorGrading