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70 lines
1.9 KiB
Plaintext
70 lines
1.9 KiB
Plaintext
2 months ago
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// Calculates adaptation to minimum/maximum luminance values,
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// based on "currently adapted" and "new values to adapt to"
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// textures (both 1x1).
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Shader "Hidden/Contrast Stretch Adaptation" {
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Properties {
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_MainTex ("Base (RGB)", 2D) = "white" {}
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_CurTex ("Base (RGB)", 2D) = "white" {}
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}
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Category {
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SubShader {
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Pass {
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ZTest Always Cull Off ZWrite Off
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Fog { Mode off }
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CGPROGRAM
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#pragma vertex vert_img
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#pragma fragment frag
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#pragma fragmentoption ARB_precision_hint_fastest
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#include "UnityCG.cginc"
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uniform sampler2D _MainTex; // currently adapted to
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uniform sampler2D _CurTex; // new value to adapt to
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uniform float4 _AdaptParams; // x=adaptLerp, y=limitMinimum, z=limitMaximum
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float4 frag (v2f_img i) : COLOR {
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// value is: max, min
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float2 valAdapted = tex2D(_MainTex, i.uv).xy;
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float2 valCur = tex2D(_CurTex, i.uv).xy;
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// Calculate new adapted values: interpolate
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// from valAdapted to valCur by script-supplied amount.
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//
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// Because we store adaptation levels in a simple 8 bit/channel
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// texture, we might not have enough precision - the interpolation
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// amount might be too small to change anything, and we'll never
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// arrive at the needed values.
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//
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// So we make sure the change we do is at least 1/255th of the
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// color range - this way we'll always change the value.
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const float kMinChange = 1.0/255.0;
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float2 delta = (valCur-valAdapted) * _AdaptParams.x;
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delta.x = sign(delta.x) * max( kMinChange, abs(delta.x) );
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delta.y = sign(delta.y) * max( kMinChange, abs(delta.y) );
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float4 valNew;
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valNew.xy = valAdapted + delta;
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// Impose user limits on maximum/minimum values
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valNew.x = max( valNew.x, _AdaptParams.z );
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valNew.y = min( valNew.y, _AdaptParams.y );
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// Optimization so that our final apply pass is faster:
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// z = max-min (plus a small amount to prevent division by zero)
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valNew.z = valNew.x - valNew.y + 0.01;
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// w = min/(max-min)
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valNew.w = valNew.y / valNew.z;
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return valNew;
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}
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ENDCG
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}
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}
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}
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Fallback off
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}
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