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Shader Study

POST PROCESSING IN COLOR

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? Flimic Tone Mapping
? Color Grading

? Image Sharpening
? Color Correction
? Photo Filter

Flimic Tone Mapping
? John Hable? Unchated2 HDR Lighting ??

???? ??? ??
? Flim??? ?? Curve? ? ?? ??? ?
???? ??? ??
? ?????? Reinhard??? ???? ?
?????? ????, ??? ??? ?
?? ??? ? ??? ??? ??

Flimic Tone Mapping
A = Shoulder Strength
B = Linear Strength
C = Linear Angle
D = Toe Strength
E = Toe Numerator
F = Toe Denominator
Note: E/F = Toe Angle

?
?

John Hable? Blog? ???, Fixed ? ????? ??.
Gamma ??? ????? ?? (pow(x, 1/2.2))

Color Grading

? ?? (HDR to LDR ??) ? ?? ?? ? ?? (LDR color to color ??) ??? ??
http://udn.epicgames.com/Three/ColorGradingKR.html

http://ttmayrin.tistory.com/34 Color Grading by LookUpTexture (?? ???? by LUT)

Color Grading
? ?? ???? RGB?? ???? UV??? ??

? ??? Color? ??? ?? ??

? ???? 16x16x16 3DTexture? ?? ???? tex3D??

?? ColorGrading? ??

? LUT? ??? ColorGrading? Post Effect??? ?

?? ?? ?? ??? ?? ???? ?????
??? ??

? Actor? ShaderCode???? LUT?? ??? ????

? ??

? ?? ??? ????? LUT? ??? ??? ?

?? ?? ???? ???, ???? ???? ?
?? ? ??
? ??? ???? ????? ??? ??

Color Grading
?? LUT ??? 256x16
16x16x16 3D ???? ???? ?? ??

1. ColorGrading? ??? ????? ???? ????? ???
2. ??? ?? LUT? ?? ???

3. ???? ?? ???? ??? ??? ??? ???? ??
- ??? ??? ?? ??? LUT? ?? ??????? ?
4. ??? ??????? LUT? ?? ??
GrayScale? LUT

256x16 LUT? ?? ShaderCode from Unreal3
float3 CalcLUT( sampler InLUT, float3 InColor )
{
// requires a volume texture 16x16x16 unwrapped in a 2d texture 256x16
// can be optimized by using a volume texture
float2 Offset = float2(0.5f / 256.0f, 0.5f / 16.0f);
float Scale = 15.0f / 16.0f;

// Also consider blur value in the blur buffer written by translucency
float IntB = floor(InColor.b * 14.9999f) / 16.0f;
float FracB = InColor.b * 15.0f - IntB * 16.0f;

float U = IntB + InColor.r * Scale / 16.0f;
float V = InColor.g * Scale;

float3 RG0 = tex2D( InLUT, Offset + float2(U
, V) ).rgb;
float3 RG1 = tex2D( InLUT, Offset + float2(U + 1.0f / 16.0f, V) ).rgb;

return lerp( RG0, RG1, FracB );
}

16x16x16 3D VolumeTexture? ??? ??
float3 CalcLUT( sampler InLUT, float3 InColor )
{
return tex3D( InLUT, InColor * 15.f / 16.f + 0.5f / 16.f ).rgb;
}

Image Sharpening

???? ???? ?? ??
Simply lerp between low-res blurred image with original image by a ratio bigger than 1
Sharp = lerp(blurred, orig, bigger than 1 ratio)

vector rcpres;
float4 lSharp(in float2 Tex : TEXCOORD) : COLOR0
{
float4 inColor = tex2D(s0, Tex);
float4 blur = inColor;

blur += tex2D(s0, float2(Tex.x, Tex.y+rcpres.y)) * 0.25;
blur += tex2D(s0, float2(Tex.x, Tex.y-rcpres.y)) * 0.25;
blur += tex2D(s0, float2(Tex.x+rcpres.x, Tex.y)) * 0.25;
blur += tex2D(s0, float2(Tex.x-rcpres.x, Tex.y)) * 0.25;
blur += tex2D(s0, float2(Tex.x-rcpres.x, Tex.y+rcpres.y)) * 0.25;
blur += tex2D(s0, float2(Tex.x-rcpres.x, Tex.y-rcpres.y)) * 0.25;
blur += tex2D(s0, float2(Tex.x+rcpres.x, Tex.y+rcpres.y)) * 0.25;
blur += tex2D(s0, float2(Tex.x+rcpres.x, Tex.y-rcpres.y)) * 0.25;
blur /= 3;

float4 final = lerp(blur,inColor, 3);
return final;
}

Color Correction
? Color range based on Euclidian distance
? ColorRange = saturate(1 - length( src - col.xyz) );

? ????? CMYK ???? ??
? c = lerp( c, clamp(c + dst_c, -1, 1), ColorRange);

? ????? ??? ?? ??? ??
? Orig =lerp( Orig, CMYKtoRGB( c), ColorRange);

Photo Filter
? ???? ???? ?? ???? ???? ??
? ????? ?? ??
? cMood = lerp(0, cMood, saturate( fLum * 2.0 ) );
? cMood = lerp(cMood, 1, saturate( fLum - 0.5 ) * 2.0 );

? ?? ??? ??(luminance)? ??? ??(user ratio)

????? ??? ??? ?? ???? ??
? final= lerp(cScreen, cMood , saturate( fLum * fRatio));

float fRatio = 0.25;
float moodR = 0.5;
float moodG = 0.4;
float moodB = 0.25; //default is a mild orange
float4 colorMood(in float2 Tex : TEXCOORD) : COLOR0
{
float4 cScreen = tex2D(s0, Tex);
float4 cMood = 1;
cMood.r = moodR;
cMood.g = moodG;
cMood.b = moodB;
float fLum = ( cScreen.r + cScreen.g + cScreen.b ) / 3;

cMood = lerp(0, cMood, saturate(fLum * 2.0));
cMood = lerp(cMood, 1, saturate(fLum - 0.5) * 2.0);
float4 final = lerp(cScreen, cMood, saturate(fLum * fRatio));
return final;
}

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Post processing in_color

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