Add HDR Mod Compatibility

shaders/config.glsl

@@ -70,7 +70,7 @@
 	|	colortex5	|   rgba16f  		|	256, 256   	|	Sky environment map
 	|	colortex6	|   rgba8           |	Full res  	|	Solid albedo, rain alpha
 	|	colortex7	|   rgba16ui        |	Full res  	|	Material data
-	|	colortex8	|   rgba16          |	Full res  	|	Normal data -> LDR output
+	|	colortex8	|   rgba16          |	Full res  	|	Normal data -> LDR output / PQ Intermediate
 	|	colortex9	|   rgba16f     	|	Full res	|	Cloud history
 	|	colortex10	|                   |				|	Unused
 	|	colortex11	|   rgba32ui        |	Half res  	|	Volumetric fog, linear depth

shaders/lib/post/ACES.glsl

@@ -394,22 +394,35 @@ vec3 RRTAndODTFit(in vec3 rgb) {
 
 	return a / b;
 }
+#ifndef HDR_ENABLED
+	vec3 AcademyFit(in vec3 rgb) {
+		rgb *= sRGB_2_AP0;
 
-vec3 AcademyFit(in vec3 rgb) {
-	rgb *= sRGB_2_AP0;
-
-	// Apply RRT sweeteners
-	rgb = RRTSweeteners(rgb);
-
-	// Apply RRT and ODT
-	rgb = RRTAndODTFit(rgb);
+		// Apply RRT sweeteners
+		rgb = RRTSweeteners(rgb);
 
-	// Global desaturation
-	rgb = mix(vec3(dot(rgb, AP1_RGB2Y)), rgb, odtSatFactor);
+		// Apply RRT and ODT
+		rgb = RRTAndODTFit(rgb);
 
-	return rgb * AP1_2_sRGB;
-}
+		// Global desaturation
+		rgb = mix(vec3(dot(rgb, AP1_RGB2Y)), rgb, odtSatFactor);
 
+		return rgb * AP1_2_sRGB;
+	}
+#else
+	// Use this simpler fit for HDR as of now.
+	// https://knarkowicz.wordpress.com/2016/08/31/hdr-display-first-steps/
+	vec3 AcademyFit(vec3 x){
+		x *= 1.2;
+		x *= sRGB_2_Rec2020;
+		float a = 15.8f;
+		float b = 2.12f;
+		float c = 1.2f;
+		float d = 5.92f;
+		float e = 1.9f;
+		return ( x * ( a * x + b ) ) / ( x * ( c * x + d ) + e ) * Rec2020_2_sRGB;
+	}
+#endif
 //======// ACES Full //===========================================================================//
 
 vec3 RRT(in vec3 aces) {

shaders/lib/post/AgX.glsl

@@ -290,3 +290,101 @@ vec3 AgXConfigurable(in vec3 rgb) {
 vec3 AgX_Full(in vec3 rgb) {
     return sRGBToLinear(AgXConfigurable(rgb));
 }
+
+//======// AgX AllenWp, for HDR/SDR use //============================================================================//
+// allenwp tonemapping curve; developed for use in the Godot game engine.
+// Source and details: https://allenwp.com/blog/2025/05/29/allenwp-tonemapping-curve/
+// Input must be a non-negative linear scene value.
+vec3 allenwp_curve(vec3 x) {
+    #ifdef HDR_ENABLED
+        float output_max_value = HdrGamePeakBrightness / HdrGamePaperWhiteBrightness;
+    #else
+        float output_max_value = 1.0;
+    #endif
+	// These constants must match the those in the C++ code that calculates the parameters.
+	// 18% "middle gray" is perceptually 50% of the brightness of reference white.
+	const float awp_crossover_point = 0.1841865;
+	const float awp_shoulder_max = output_max_value - awp_crossover_point;
+    float awp_high_clip = 12.0;
+    awp_high_clip = max(awp_high_clip, output_max_value);
+	float awp_contrast = 1.5;
+	float awp_toe_a = ((1.0 / awp_crossover_point) - 1.0) * pow(awp_crossover_point, awp_contrast);
+    float awp_slope_denom = pow(awp_crossover_point, awp_contrast) + awp_toe_a;
+	float awp_slope = (awp_contrast * pow(awp_crossover_point, awp_contrast - 1.0) * awp_toe_a) / (awp_slope_denom * awp_slope_denom);
+	float awp_w = awp_high_clip - awp_crossover_point;
+	awp_w = awp_w * awp_w;
+	awp_w = awp_w / awp_shoulder_max;
+	awp_w = awp_w * awp_slope;
+
+	// Reinhard-like shoulder:
+	vec3 s = x - awp_crossover_point;
+	vec3 slope_s = awp_slope * s;
+	s = slope_s * (1.0 + s / awp_w) / (1.0 + (slope_s / awp_shoulder_max));
+	s += awp_crossover_point;
+
+	// Sigmoid power function toe:
+	vec3 t = pow(x, vec3(awp_contrast));
+	t = t / (t + awp_toe_a);
+
+	return mix(s, t, lessThan(x, vec3(awp_crossover_point)));
+}
+
+// This is an approximation and simplification of EaryChow's AgX implementation that is used by Blender.
+// This code is based off of the script that generates the AgX_Base_sRGB.cube LUT that Blender uses.
+// Source: https://github.com/EaryChow/AgX_LUT_Gen/blob/main/AgXBasesRGB.py
+// Colorspace transformation source: https://www.colour-science.org:8010/apps/rgb_colourspace_transformation_matrix
+vec3 AgX_AllenWp(vec3 color) {
+	// Input color should be non-negative!
+	// Large negative values in one channel and large positive values in other
+	// channels can result in a colour that appears darker and more saturated than
+	// desired after passing it through the inset matrix. For this reason, it is
+	// best to prevent negative input values.
+	// This is done before the Rec. 2020 transform to allow the Rec. 2020
+	// transform to be combined with the AgX inset matrix. This results in a loss
+	// of color information that could be correctly interpreted within the
+	// Rec. 2020 color space as positive RGB values, but is often not worth
+	// the performance cost of an additional matrix multiplication.
+	//
+	// Additionally, this AgX configuration was created subjectively based on
+	// output appearance in the Rec. 709 color gamut, so it is possible that these
+	// matrices will not perform well with non-Rec. 709 output (more testing with
+	// future wide-gamut displays is be needed).
+	// See this comment from the author on the decisions made to create the matrices:
+	// https://github.com/godotengine/godot-proposals/issues/12317#issuecomment-2835824250
+
+	// Combined Rec. 709 to Rec. 2020 and Blender AgX inset matrices:
+	const mat3 rec709_to_rec2020_agx_inset_matrix = mat3(
+			0.544814746488245, 0.140416948464053, 0.0888104196149096,
+			0.373787398372697, 0.754137554567394, 0.178871756420858,
+			0.0813978551390581, 0.105445496968552, 0.732317823964232);
+
+	// Combined inverse AgX outset matrix and Rec. 2020 to Rec. 709 matrices.
+	const mat3 agx_outset_rec2020_to_rec709_matrix = mat3(
+			1.96488741169489, -0.299313364904742, -0.164352742528393,
+			-0.855988495690215, 1.32639796461980, -0.238183969428088,
+			-0.108898916004672, -0.0270845997150571, 1.40253671195648);
+    #ifdef HDR_ENABLED
+	    float output_max_value = HdrGamePeakBrightness / HdrGamePaperWhiteBrightness;
+    #else
+        float output_max_value = 1.0;
+    #endif
+
+    // Apply inset matrix.
+	color = rec709_to_rec2020_agx_inset_matrix * color * 2.0;
+
+	// Use the allenwp tonemapping curve to match the Blender AgX curve while
+	// providing stability across all variable dyanimc range (SDR, HDR, EDR).
+	color = allenwp_curve(color);
+
+	// Clipping to output_max_value is required to address a cyan colour that occurs
+	// with very bright inputs.
+	color = min(vec3(output_max_value), color);
+
+	// Apply outset to make the result more chroma-laden and then go back to Rec. 709.
+	color = agx_outset_rec2020_to_rec709_matrix * color;
+
+	// Blender's lusRGB.compensate_low_side is too complex for this shader, so
+	// simply return the color, even if it has negative components. These negative
+	// components may be useful for subsequent color adjustments.
+    return color;
+}

shaders/lib/post/GT.glsl

@@ -4,7 +4,11 @@
 // Math: https://www.desmos.com/calculator/gslcdxvipg
 // Source: https://www.slideshare.net/nikuque/hdr-theory-and-practicce-jp
 vec3 GT(in vec3 x) {
-    const float maxDisplayBrightness = 1.0;
+    #ifdef HDR_ENABLED
+        float maxDisplayBrightness = HdrGamePeakBrightness / HdrGamePaperWhiteBrightness;
+    #else
+        const float maxDisplayBrightness = 1.0;
+    #endif
     const float contrast			 = 1.0;
     const float linearStart			 = 0.2;
     const float linearLength		 = 0.1;
@@ -432,9 +436,13 @@ vec3 GT7(in vec3 color) {
     color *= sRGB_2_Rec2020;
 
     GT7ToneMapping tm;
-    initializeAsSDR(tm);
+    #ifdef HDR_ENABLED
+        initializeAsHDR(HdrGamePeakBrightness,tm);
+    #else
+        initializeAsSDR(tm);
+    #endif
 
     applyToneMapping(color, tm);
 
     return color * Rec2020_2_sRGB;
-}
+}

shaders/lib/universal/Uniform.glsl

@@ -206,3 +206,9 @@ uniform vec3 viewLightVector;
     #define lodProjectionInv gbufferProjectionInverse
     #define lodPrevProjection gbufferPreviousProjection
 #endif
+
+#ifdef HDR_ENABLED
+    uniform float HdrGamePeakBrightness;
+    uniform float HdrGamePaperWhiteBrightness;
+    uniform float HdrUIBrightness;
+#endif

shaders/lib/utility/Color.glsl

@@ -35,6 +35,26 @@ const mat3 Rec2020_2_XYZ = mat3(
     0.0000000000, 0.0280726930, 1.0609850577
 );
 
+// https://en.wikipedia.org/wiki/Perceptual_quantizer
+const float PQ_M1 = 2610.0/4096 * 1.0/4;
+const float PQ_M2 = 2523.0/4096 * 128;
+const float PQ_C1 = 3424.0/4096;
+const float PQ_C2 = 2413.0/4096 * 32;
+const float PQ_C3 = 2392.0/4096 * 32;
+
+vec3 linearToPq(vec3 c, float scaling) {
+    c *= scaling / 10000.0;
+    c = pow(c, vec3(PQ_M1));
+    c = (vec3(PQ_C1) + vec3(PQ_C2) * c) / (vec3(1.0) + vec3(PQ_C3) * c);
+    return pow(c, vec3(PQ_M2));
+}
+
+vec3 PqToLinear(vec3 color, float scaling) {
+    vec3 e_m12 = pow(color, vec3(1.0 / PQ_M2));
+    vec3 out_color = pow(max(vec3(0), e_m12 - PQ_C1) / (PQ_C2 - PQ_C3 * e_m12), vec3(1.0 / PQ_M1));
+    return out_color * (10000.0 / scaling);
+}
+
 // https://en.wikipedia.org/wiki/SRGB
 // https://github.com/tobspr/GLSL-Color-Spaces/blob/master/ColorSpaces.inc.glsl
 vec3 linearToSRGB(in vec3 color) {
@@ -45,6 +65,21 @@ vec3 sRGBToLinear(in vec3 color) {
 	return mix(color * 0.07739938, pow((color + 0.055) * 0.94786729, vec3(2.4)), step(vec3(0.04045), color));
 }
 
+// https://en.wikipedia.org/wiki/SRGB
+// https://en.wikipedia.org/wiki/ScRGB
+// -f(-x) for negative values.
+vec3 sRGBToLinearSafe(in vec3 color) {
+    vec3 color_sign = sign(color);
+    vec3 color_abs = abs(color);
+	return mix(color_abs * 0.07739938, pow((color_abs + 0.055) * 0.94786729, vec3(2.4)), step(vec3(0.04045), color_abs)) * color_sign;
+}
+
+vec3 linearToSRGBSafe(in vec3 color) {
+    vec3 color_sign = sign(color);
+    vec3 color_abs = abs(color);
+	return mix(color_abs * 12.92, 1.055 * pow(color_abs, vec3(0.41666666)) - 0.055, step(vec3(0.0031308), color_abs)) * color_sign;
+}
+
 // https://chilliant.blogspot.com/2012/08/srgb-approximations-for-hlsl.html
 vec3 linearToSRGBApprox(in vec3 color) {
     vec3 S1 = color * inversesqrt(color);

shaders/program/post/Final.frag

@@ -40,9 +40,21 @@ out vec3 finalOut;
 // Reference: Lou Kramer, FidelityFX CAS, AMD Developer Day 2019,
 // https://gpuopen.com/wp-content/uploads/2019/07/FidelityFX-CAS.pptx
 // https://github.com/GPUOpen-Effects/FidelityFX-CAS
-vec3 FFXCasFilter(in ivec2 texel, in float sharpness) {
-	#define CasLoad(offset) texelFetchOffset(colortex8, texel, 0, offset).rgb
+vec3 AFromPq(in vec3 color) {
+	vec3 p = pow(color, vec3(0.0126833));
+	return pow(saturate(p - vec3(0.835938))/(vec3(18.8516) - vec3(18.6875)*p), vec3(6.27739));
+}
 
+vec3 AToPq(in vec3 color) {
+	vec3 p = pow(color, vec3(0.159302));
+	return pow((vec3(0.835938) + vec3(18.8516) * p)/(vec3(1.0)+vec3(18.6875)*p),vec3(78.8438));
+}
+vec3 FFXCasFilter(in ivec2 texel, in float sharpness) {
+	#ifdef HDR_ENABLED
+		#define CasLoad(offset) AFromPq(texelFetchOffset(colortex8, texel, 0, offset).rgb)
+	#else
+		#define CasLoad(offset) texelFetchOffset(colortex8, texel, 0, offset).rgb
+	#endif
 	#ifndef CAS_ENABLED
 		return CasLoad(ivec2(0, 0));
 	#endif
@@ -93,6 +105,7 @@ void HistogramDisplay(inout vec3 color, in ivec2 texel) {
 	}
 }
 
+
 //======// Main //================================================================================//
 void main() {
     ivec2 texelPos = ivec2(gl_FragCoord.xy);
@@ -103,7 +116,12 @@ void main() {
 	#ifdef DEBUG_BLOOM_TILES
 		finalOut = texelFetch(colortex4, texelPos, 0).rgb;
 	#else
-		finalOut = FFXCasFilter(texelPos, CAS_STRENGTH);
+		#ifdef HDR_ENABLED
+			// PQ decode back up to game brightness after CAS 
+			finalOut = linearToSRGBSafe(PqToLinear(AToPq(FFXCasFilter(texelPos, CAS_STRENGTH)), HdrUIBrightness) * Rec2020_2_sRGB);
+		#else
+			finalOut = FFXCasFilter(texelPos, CAS_STRENGTH);
+		#endif
 	#endif
 
 	// Text display
@@ -143,6 +161,8 @@ void main() {
 		HistogramDisplay(finalOut, texelPos);
 	#endif
 
-	// Apply bayer dithering to reduce banding artifacts
-	finalOut += (bayer16(gl_FragCoord.xy) - 0.5) * rcp255;
+	#ifndef HDR_ENABLED
+		// Apply bayer dithering to reduce banding artifacts
+		finalOut += (bayer16(gl_FragCoord.xy) - 0.5) * rcp255;
+	#endif
 }

shaders/program/post/Grade.comp

@@ -20,7 +20,7 @@ const vec2 workGroupsRender = vec2(1.0, 1.0);
 
 #include "/lib/Utility.glsl"
 
-#define TONE_MAPPER AgX_Minimal // [None AcademyFit AcademyFull AgX_Minimal AgX_Full Lottes GT GT7]
+#define TONE_MAPPER GT7 // [None AcademyFit AcademyFull AgX_AllenWp AgX_Minimal AgX_Full Lottes GT GT7]
 
 #define BLOOM_BLENDING_MODE 1 // [0 1 2]
 #define BLOOM_INTENSITY 1.0 // [0.0 0.01 0.02 0.05 0.07 0.1 0.15 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 3.0 4.0 5.0 7.0 10.0 15.0 20.0]
@@ -39,7 +39,7 @@ const vec2 workGroupsRender = vec2(1.0, 1.0);
 
 //======// Uniform //=============================================================================//
 
-writeonly uniform image2D colorimg8; // LDR output
+writeonly uniform image2D colorimg8; // LDR / Tonemapped HDR output
 
 #include "/lib/universal/Uniform.glsl"
 
@@ -206,7 +206,14 @@ void main() {
 		// color *= Rec2020_2_sRGB;
 
 		// Working to display space
-		color = saturate(linearToSRGB(color));
+		#ifdef HDR_ENABLED
+			// Normalize for FFX CAS using PQ encoding
+			color *= sRGB_2_Rec2020;
+			color = max(vec3(0.0), color); // Avoid negative values causing issues with PQ encoding
+			color = saturate(linearToPq(color, HdrGamePaperWhiteBrightness));
+		#else
+			color = saturate(linearToSRGB(color));
+		#endif
 	}
 
 	// Debug tone mapping plot