Add a new high quality tonemapper: ACES Fitted (3.x)

doc/classes/Environment.xml

@@ -337,7 +337,10 @@
 			Filmic tonemapper operator.
 		</constant>
 		<constant name="TONE_MAPPER_ACES" value="3" enum="ToneMapper">
-			Academy Color Encoding System tonemapper operator.
+			Academy Color Encoding System tonemapper operator. Performs an aproximation of the ACES tonemapping curve.
+		</constant>
+		<constant name="TONE_MAPPER_ACES_FITTED" value="4" enum="ToneMapper">
+			High quality Academy Color Encoding System tonemapper operator that matches the industry standard. Performs a more physically accurate curve fit which better simulates how light works in the real world. The color of lights and emissive materials will become lighter as the emissive energy increases, and will eventually become white if the light is bright enough to saturate the camera sensor.
 		</constant>
 		<constant name="DOF_BLUR_QUALITY_LOW" value="0" enum="DOFBlurQuality">
 			Low depth-of-field blur quality (fastest).

doc/classes/VisualServer.xml

@@ -3798,6 +3798,9 @@
 		<constant name="ENV_TONE_MAPPER_ACES" value="3" enum="EnvironmentToneMapper">
 			Use the ACES tonemapper.
 		</constant>
+		<constant name="ENV_TONE_MAPPER_ACES_FITTED" value="4" enum="EnvironmentToneMapper">
+			Use the ACES Fitted tonemapper.
+		</constant>
 		<constant name="ENV_SSAO_QUALITY_LOW" value="0" enum="EnvironmentSSAOQuality">
 			Lowest quality of screen space ambient occlusion.
 		</constant>

drivers/gles3/rasterizer_scene_gles3.cpp

@@ -3863,6 +3863,7 @@ void RasterizerSceneGLES3::_post_process(Environment *env, const CameraMatrix &p
 	if (env) {
 		state.tonemap_shader.set_conditional(TonemapShaderGLES3::USE_FILMIC_TONEMAPPER, env->tone_mapper == VS::ENV_TONE_MAPPER_FILMIC);
 		state.tonemap_shader.set_conditional(TonemapShaderGLES3::USE_ACES_TONEMAPPER, env->tone_mapper == VS::ENV_TONE_MAPPER_ACES);
+		state.tonemap_shader.set_conditional(TonemapShaderGLES3::USE_ACES_FITTED_TONEMAPPER, env->tone_mapper == VS::ENV_TONE_MAPPER_ACES_FITTED);
 		state.tonemap_shader.set_conditional(TonemapShaderGLES3::USE_REINHARD_TONEMAPPER, env->tone_mapper == VS::ENV_TONE_MAPPER_REINHARD);
 		state.tonemap_shader.set_conditional(TonemapShaderGLES3::USE_AUTO_EXPOSURE, env->auto_exposure);
 		state.tonemap_shader.set_conditional(TonemapShaderGLES3::USE_GLOW_FILTER_BICUBIC, env->glow_bicubic_upscale);
@@ -3964,6 +3965,7 @@ void RasterizerSceneGLES3::_post_process(Environment *env, const CameraMatrix &p
 	state.tonemap_shader.set_conditional(TonemapShaderGLES3::USE_AUTO_EXPOSURE, false);
 	state.tonemap_shader.set_conditional(TonemapShaderGLES3::USE_FILMIC_TONEMAPPER, false);
 	state.tonemap_shader.set_conditional(TonemapShaderGLES3::USE_ACES_TONEMAPPER, false);
+	state.tonemap_shader.set_conditional(TonemapShaderGLES3::USE_ACES_FITTED_TONEMAPPER, false);
 	state.tonemap_shader.set_conditional(TonemapShaderGLES3::USE_REINHARD_TONEMAPPER, false);
 	state.tonemap_shader.set_conditional(TonemapShaderGLES3::USE_GLOW_LEVEL1, false);
 	state.tonemap_shader.set_conditional(TonemapShaderGLES3::USE_GLOW_LEVEL2, false);

drivers/gles3/shaders/tonemap.glsl

@@ -163,6 +163,37 @@ vec3 tonemap_aces(vec3 color, float white) {
 	return clamp(color_tonemapped / white_tonemapped, vec3(0.0f), vec3(1.0f));
 }
 
+// Adapted from https://github.com/TheRealMJP/BakingLab/blob/master/BakingLab/ACES.hlsl
+// (MIT License).
+vec3 tonemap_aces_fitted(vec3 color, float white) {
+	const float exposure_bias = 1.8f;
+	const float A = 0.0245786f;
+	const float B = 0.000090537f;
+	const float C = 0.983729f;
+	const float D = 0.432951f;
+	const float E = 0.238081f;
+
+	// Exposure bias baked into transform to save shader instructions. Equivalent to `color *= exposure_bias`
+	const mat3 rgb_to_rrt = mat3(
+			vec3(0.59719f * exposure_bias, 0.35458f * exposure_bias, 0.04823f * exposure_bias),
+			vec3(0.07600f * exposure_bias, 0.90834f * exposure_bias, 0.01566f * exposure_bias),
+			vec3(0.02840f * exposure_bias, 0.13383f * exposure_bias, 0.83777f * exposure_bias));
+
+	const mat3 odt_to_rgb = mat3(
+			vec3(1.60475f, -0.53108f, -0.07367f),
+			vec3(-0.10208f, 1.10813f, -0.00605f),
+			vec3(-0.00327f, -0.07276f, 1.07602f));
+
+	color *= rgb_to_rrt;
+	vec3 color_tonemapped = (color * (color + A) - B) / (color * (C * color + D) + E);
+	color_tonemapped *= odt_to_rgb;
+
+	white *= exposure_bias;
+	float white_tonemapped = (white * (white + A) - B) / (white * (C * white + D) + E);
+
+	return clamp(color_tonemapped / white_tonemapped, vec3(0.0f), vec3(1.0f));
+}
+
 vec3 tonemap_reinhard(vec3 color, float white) {
 	return clamp((white * color + color) / (color * white + white), vec3(0.0f), vec3(1.0f));
 }
@@ -174,6 +205,12 @@ vec3 linear_to_srgb(vec3 color) { // convert linear rgb to srgb, assumes clamped
 
 // inputs are LINEAR, If Linear tonemapping is selected no transform is performed else outputs are clamped [0, 1] color
 vec3 apply_tonemapping(vec3 color, float white) {
+	// Ensure color values are positive.
+	// They can be negative in the case of negative lights, which leads to undesired behavior.
+#if defined(USE_REINHARD_TONEMAPPER) || defined(USE_FILMIC_TONEMAPPER) || defined(USE_ACES_TONEMAPPER) || defined(USE_ACES_FITTED_TONEMAPPER)
+	color = max(vec3(0.0f), color);
+#endif
+
 #ifdef USE_REINHARD_TONEMAPPER
 	return tonemap_reinhard(color, white);
 #endif
@@ -186,6 +223,10 @@ vec3 apply_tonemapping(vec3 color, float white) {
 	return tonemap_aces(color, white);
 #endif
 
+#ifdef USE_ACES_FITTED_TONEMAPPER
+	return tonemap_aces_fitted(color, white);
+#endif
+
 	return color; // no other selected -> linear: no color transform applied
 }
 
@@ -401,9 +442,7 @@ void main() {
 #endif
 
 	// Early Tonemap & SRGB Conversion; note that Linear tonemapping does not clamp to [0, 1]; some operations below expect a [0, 1] range and will clamp
-	// Ensure color values are positive.
-	// They can be negative in the case of negative lights, which leads to undesired behavior.
-	color = apply_tonemapping(max(vec3(0.0), color), white);
+	color = apply_tonemapping(color, white);
 
 #ifdef KEEP_3D_LINEAR
 	// leave color as is (-> don't convert to SRGB)

scene/resources/environment.cpp

@@ -919,7 +919,7 @@ void Environment::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("get_tonemap_auto_exposure_grey"), &Environment::get_tonemap_auto_exposure_grey);
 
 	ADD_GROUP("Tonemap", "tonemap_");
-	ADD_PROPERTY(PropertyInfo(Variant::INT, "tonemap_mode", PROPERTY_HINT_ENUM, "Linear,Reinhard,Filmic,ACES"), "set_tonemapper", "get_tonemapper");
+	ADD_PROPERTY(PropertyInfo(Variant::INT, "tonemap_mode", PROPERTY_HINT_ENUM, "Linear,Reinhard,Filmic,ACES,ACES Fitted"), "set_tonemapper", "get_tonemapper");
 	ADD_PROPERTY(PropertyInfo(Variant::REAL, "tonemap_exposure", PROPERTY_HINT_RANGE, "0,16,0.01"), "set_tonemap_exposure", "get_tonemap_exposure");
 	ADD_PROPERTY(PropertyInfo(Variant::REAL, "tonemap_white", PROPERTY_HINT_RANGE, "0,16,0.01"), "set_tonemap_white", "get_tonemap_white");
 	ADD_GROUP("Auto Exposure", "auto_exposure_");
@@ -1138,6 +1138,7 @@ void Environment::_bind_methods() {
 	BIND_ENUM_CONSTANT(TONE_MAPPER_REINHARDT);
 	BIND_ENUM_CONSTANT(TONE_MAPPER_FILMIC);
 	BIND_ENUM_CONSTANT(TONE_MAPPER_ACES);
+	BIND_ENUM_CONSTANT(TONE_MAPPER_ACES_FITTED);
 
 	BIND_ENUM_CONSTANT(DOF_BLUR_QUALITY_LOW);
 	BIND_ENUM_CONSTANT(DOF_BLUR_QUALITY_MEDIUM);

scene/resources/environment.h

@@ -56,7 +56,8 @@ class Environment : public Resource {
 		TONE_MAPPER_LINEAR,
 		TONE_MAPPER_REINHARDT,
 		TONE_MAPPER_FILMIC,
-		TONE_MAPPER_ACES
+		TONE_MAPPER_ACES,
+		TONE_MAPPER_ACES_FITTED
 	};
 
 	enum GlowBlendMode {

servers/visual_server.cpp

@@ -2504,6 +2504,7 @@ void VisualServer::_bind_methods() {
 	BIND_ENUM_CONSTANT(ENV_TONE_MAPPER_REINHARD);
 	BIND_ENUM_CONSTANT(ENV_TONE_MAPPER_FILMIC);
 	BIND_ENUM_CONSTANT(ENV_TONE_MAPPER_ACES);
+	BIND_ENUM_CONSTANT(ENV_TONE_MAPPER_ACES_FITTED);
 
 	BIND_ENUM_CONSTANT(ENV_SSAO_QUALITY_LOW);
 	BIND_ENUM_CONSTANT(ENV_SSAO_QUALITY_MEDIUM);

servers/visual_server.h

@@ -778,7 +778,8 @@ class VisualServer : public Object {
 		ENV_TONE_MAPPER_LINEAR,
 		ENV_TONE_MAPPER_REINHARD,
 		ENV_TONE_MAPPER_FILMIC,
-		ENV_TONE_MAPPER_ACES
+		ENV_TONE_MAPPER_ACES,
+		ENV_TONE_MAPPER_ACES_FITTED
 	};
 
 	virtual void environment_set_tonemap(RID p_env, EnvironmentToneMapper p_tone_mapper, float p_exposure, float p_white, bool p_auto_exposure, float p_min_luminance, float p_max_luminance, float p_auto_exp_speed, float p_auto_exp_grey) = 0;