From 6374a4b274e5048c56a820402275e28cf5ac1d39 Mon Sep 17 00:00:00 2001
From: Andrew Opalach <andrew@akon.city>
Date: Mon, 29 Jun 2026 11:15:01 -0400
Subject: Cleanup and test some lighting stuff

Signed-off-by: Andrew Opalach <andrew@akon.city>
---
 Shaders/alpha_as_luma.hlsl | 58 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 Shaders/alpha_as_luma.hlsl

(limited to 'Shaders/alpha_as_luma.hlsl')

diff --git a/Shaders/alpha_as_luma.hlsl b/Shaders/alpha_as_luma.hlsl
new file mode 100644
index 0000000..525f3c6
--- /dev/null
+++ b/Shaders/alpha_as_luma.hlsl
@@ -0,0 +1,58 @@
+// https://stackoverflow.com/a/37624009
+float inverseGamma(float t)
+{
+    return ((t <= 0.0404482362771076) ? (t/12.92) : pow((t + 0.055)/1.055, 2.4));
+}
+
+// CIE L*a*b* f function (used to convert XYZ to L*a*b*)
+// http://en.wikipedia.org/wiki/Lab_color_space
+float LABF(float t)
+{
+    return ((t >= 8.85645167903563082e-3) ? pow(t, (1.0/3.0)) : (841.0/108.0)*t + (4.0/29.0));
+}
+
+float rgbToCIEL(float3 p)
+{
+    float r = inverseGamma(p.r);
+    float g = inverseGamma(p.g);
+    float b = inverseGamma(p.b);
+
+    // Observer = 2°, Illuminant = D65
+    float y = 0.2125862307855955516*r + 0.7151703037034108499*g + 0.07220049864333622685*b;
+
+    // At this point we've done RGBtoXYZ now do XYZ to Lab
+
+    // y /= WHITEPOINT_Y; The white point for y in D65 is 1.0
+    y = LABF(y);
+
+    // This is the "normal" conversion which produces values scaled to 100
+    // Lab.L = 116.0*y - 16.0;
+    return 1.16*y - 0.16;
+}
+
+// ---- Created with 3Dmigoto v1.4.9 on Sun Jun 28 13:42:41 2026
+
+cbuffer CBSystem : register(b3)
+{
+    uint4 iRegion : packoffset(c0);
+    float fSourceMipLevel : packoffset(c1) = {0};
+    float fGammaCorrect : packoffset(c1.y) = {0.454545468};
+    float fGammaCorrectEx : packoffset(c1.z) = {1};
+}
+
+SamplerState SSSystemCopy : register(s0);
+Texture2D<float4> tBaseMap : register(t0);
+
+void main(
+    float4 v0 : SV_POSITION0,
+    float2 v1 : TexCoord0,
+    out float4 o0 : SV_TARGET0)
+{
+    float4 r0;
+    r0.xyz = tBaseMap.SampleLevel(SSSystemCopy, v1.xy, fSourceMipLevel).xyz;
+    o0.w = rgbToCIEL(r0.xyz);
+    //o0.w = sqrt(dot(r0.xyz, float3(0.298999995, 0.587000012, 0.114)));
+    //o0.w = dot(r0.xyz, float3(0.298999995, 0.587000012, 0.114));
+    o0.xyz = r0.xyz;
+    return;
+}
-- 
cgit v1.2.3-101-g0448