Fix Volumetric Nebula Bugs and Add Smoothing (#6854)

* Fix 3d tex generation

* Fix blending and emissive

* Add Smoothing

* Add smoothing parameter

* Correctly calculate fractional smoothing

Author: BMagnu

code/def_files/data/effects/volumetric-f.sdr

@@ -100,8 +100,6 @@ void main()
 		vec3 sampleposition = position / nebSize + 0.5;
 		vec4 volume_sample = textureGrad(volume_tex, sampleposition, gradX, gradY);
 
-		float stepsize_current = min(max(stepsize, volume_sample.x * udfScale), mintMax - stept);
-
 #ifdef DO_EDGE_SMOOTHING
 		//Average 3D texel with texels on corner, in an attempt to reduce jagged edges.
 		float stepcolor_alpha = volume_sample.a;
@@ -121,6 +119,8 @@ void main()
 		float stepcolor_alpha = volume_sample.a;
 #endif
 
+		float stepsize_current = min(max(stepsize, step(stepcolor_alpha, 0.01) * volume_sample.x * udfScale), mintMax - stept);
+
 		float stepalpha = -(pow(alphalim, 1.0 / (opacitydistance / stepsize_current)) - 1.0f) * stepcolor_alpha;
 		//All the following computations are just required if we have a stepcoloralpha that is non-zero.
 		if(stepcolor_alpha > 0.01)
@@ -151,7 +151,7 @@ void main()
 			//Emissive
 			cumnebdist += stepcolor_alpha * stepsize_current;
 			vec3 emissive_lod = textureLod(emissive, fragTexCoord.xy, clamp(cumnebdist * emissiveSpreadFactor, 0, float(textureQueryLevels(emissive) - 1))).rgb;
-			vec3 stepcolor_emissive = emissive_lod.rgb * pow(alphalim, 1.0 / (opacitydistance / ((depth - stept) * emissiveFalloff + 0.01))) * emissiveIntensity;
+			vec3 stepcolor_emissive = clamp(emissive_lod.rgb * pow(alphalim, 1.0 / (opacitydistance / ((depth - stept) * emissiveFalloff + 0.01))) * emissiveIntensity, 0, 1);
 
 			//Step finish
 			vec3 stepcolor = clamp(stepcolor_diffuse + stepcolor_emissive, 0, 1);
@@ -165,7 +165,5 @@ void main()
 			break;
 	}
 
-	cumcolor += cumOMAlpha * color_in.rgb;
-
-	fragOut0 = vec4(cumcolor, 1);
+	fragOut0 = vec4(cumOMAlpha * color_in.rgb + ((1.0 - cumOMAlpha) * cumcolor), 1);
 }

code/nebula/volumetrics.cpp

@@ -55,6 +55,10 @@ volumetric_nebula& volumetric_nebula::parse_volumetric_nebula() {
 		stuff_int(&oversampling);
 	}
 
+	if (optional_string("+Smoothing:")) {
+		stuff_float(&smoothing);
+	}
+
 	//Lighting settings
 	if (optional_string("+Heyney Greenstein Coefficient:")) {
 		stuff_float(&henyeyGreensteinCoeff);
@@ -155,6 +159,10 @@ const std::tuple<float, float, float>& volumetric_nebula::getNebulaColor() const
 	return nebulaColor;
 }
 
+int volumetric_nebula::getVolumeBitmapSmoothingSteps() const {
+	return std::max(1, static_cast<int>(static_cast<float>(1 << (resolution + oversampling - 1)) * std::min(smoothing, 0.5f)));
+}
+
 bool volumetric_nebula::getEdgeSmoothing() const {
 	return Detail.nebula_detail == MAX_DETAIL_VALUE || doEdgeSmoothing; //Only for highest setting, or when the lab has an override.
 }
@@ -208,7 +216,7 @@ float volumetric_nebula::getGlobalLightDistanceFactor() const {
 }
 
 float volumetric_nebula::getGlobalLightStepsize() const {
-	return getOpacityDistance() / static_cast<float>(getGlobalLightSteps()) * getGlobalLightDistanceFactor();
+	return getOpacityDistance() * static_cast<float>(getVolumeBitmapSmoothingSteps()) / static_cast<float>(getGlobalLightSteps()) * getGlobalLightDistanceFactor();
 }
 
 bool volumetric_nebula::getNoiseActive() const {
@@ -354,16 +362,22 @@ void volumetric_nebula::renderVolumeBitmap() {
 
 	//Sample the nebula values from the binary cubegrid.
 	volumeBitmapData = make_unique<ubyte[]>(n * n * n * 4);
-	int oversamplingCount = (1 << (oversampling - 1)) + 1;
-	float oversamplingDivisor = 255.1f / static_cast<float>(oversamplingCount);
+	int oversamplingCount = (1 << (oversampling - 1));
+
+	int smoothing_steps = getVolumeBitmapSmoothingSteps();
+	float oversamplingDivisor = 255.1f / (static_cast<float>(oversamplingCount + smoothing_steps) * static_cast<float>(oversamplingCount + smoothing_steps) * static_cast<float>(oversamplingCount + smoothing_steps));
+	int smoothStart = smoothing_steps / 2;
+	int smoothStop = (smoothing_steps / 2 + (1 & smoothing_steps));
+
 	for (int x = 0; x < n; x++) {
 		for (int y = 0; y < n; y++) {
 			for (int z = 0; z < n; z++) {
 				int sum = 0;
-				for (int sx = x * oversampling; sx <= (x + 1) * oversampling; sx++) {
-					for (int sy = y * oversampling; sy <= (y + 1) * oversampling; sy++) {
-						for (int sz = z * oversampling; sz <= (z + 1) * oversampling; sz++) {
-							if (volumeSampleCache[sx * nSample * nSample + sy * nSample + sz])
+				for (int sx = x * oversamplingCount - smoothStart; sx < (x + 1) * oversamplingCount + smoothStop; sx++) {
+					for (int sy = y * oversamplingCount - smoothStart; sy < (y + 1) * oversamplingCount + smoothStop; sy++) {
+						for (int sz = z * oversamplingCount - smoothStart; sz < (z + 1) * oversamplingCount + smoothStop; sz++) {
+							if (sx >= 0 && sx < nSample && sy >= 0 && sy < nSample && sz >= 0 && sz < nSample &&
+								volumeSampleCache[sx * nSample * nSample + sy * nSample + sz])
 								sum++;
 						}
 					}

code/nebula/volumetrics.h

@@ -34,6 +34,8 @@ class volumetric_nebula {
 	int resolution = 6;
 	//Oversampling of 3D-Texture. Will quadruple loading computation time for each increment, but improves banding especially at lower resolutions. 1 - 3. Mostly Loading time cost.
 	int oversampling = 2;
+	//How much the edge of the POF should be smoothed to be less hard
+	float smoothing = 0.f;
 	//Resolution of Noise 3D-Texture as 2^n. 5 - 8 recommended. Mostly VRAM cost
 	int noiseResolution = 5;
 
@@ -95,6 +97,8 @@ class volumetric_nebula {
 	const vec3d& getSize() const;
 	const std::tuple<float, float, float>& getNebulaColor() const;
 
+	int getVolumeBitmapSmoothingSteps() const;
+
 	bool getEdgeSmoothing() const;
 	int getSteps() const;
 	int getGlobalLightSteps() const;

fred2/missionsave.cpp

@@ -2794,6 +2794,7 @@ int CFred_mission_save::save_mission_info()
 			FRED_ENSURE_PROPERTY_VERSION_WITH_DEFAULT("+Steps:", 1, ";;FSO 23.1.0;;", 15, " %d", The_mission.volumetrics->steps);
 			FRED_ENSURE_PROPERTY_VERSION_WITH_DEFAULT("+Resolution:", 1, ";;FSO 23.1.0;;", 6, " %d", The_mission.volumetrics->resolution);
 			FRED_ENSURE_PROPERTY_VERSION_WITH_DEFAULT("+Oversampling:", 1, ";;FSO 23.1.0;;", 2, " %d", The_mission.volumetrics->oversampling);
+			FRED_ENSURE_PROPERTY_VERSION_WITH_DEFAULT("+Smoothing:", 1, ";;FSO 25.0.0;;", 0.f, " %f", The_mission.volumetrics->smoothing);
 			FRED_ENSURE_PROPERTY_VERSION_WITH_DEFAULT_F("+Heyney Greenstein Coefficient:", 1, ";;FSO 23.1.0;;", 0.2f, " %f", The_mission.volumetrics->henyeyGreensteinCoeff);
 			FRED_ENSURE_PROPERTY_VERSION_WITH_DEFAULT_F("+Sun Falloff Factor:", 1, ";;FSO 23.1.0;;", 1.0f, " %f", The_mission.volumetrics->globalLightDistanceFactor);
 			FRED_ENSURE_PROPERTY_VERSION_WITH_DEFAULT("+Sun Steps:", 1, ";;FSO 23.1.0;;", 6, " %d", The_mission.volumetrics->globalLightSteps);
@@ -2831,6 +2832,7 @@ int CFred_mission_save::save_mission_info()
 			bypass_comment(";;FSO 23.1.0;; +Steps:");
 			bypass_comment(";;FSO 23.1.0;; +Resolution:");
 			bypass_comment(";;FSO 23.1.0;; +Oversampling:");
+			bypass_comment(";;FSO 25.0.0;; +Smoothing:");
 			bypass_comment(";;FSO 23.1.0;; +Heyney Greenstein Coefficient:");
 			bypass_comment(";;FSO 23.1.0;; +Sun Falloff Factor:");
 			bypass_comment(";;FSO 23.1.0;; +Sun Steps:");

qtfred/src/mission/missionsave.cpp

@@ -2684,6 +2684,7 @@ int CFred_mission_save::save_mission_info()
 			FRED_ENSURE_PROPERTY_VERSION_WITH_DEFAULT("+Steps:", 1, ";;FSO 23.1.0;;", 15, " %d", The_mission.volumetrics->steps);
 			FRED_ENSURE_PROPERTY_VERSION_WITH_DEFAULT("+Resolution:", 1, ";;FSO 23.1.0;;", 6, " %d", The_mission.volumetrics->resolution);
 			FRED_ENSURE_PROPERTY_VERSION_WITH_DEFAULT("+Oversampling:", 1, ";;FSO 23.1.0;;", 2, " %d", The_mission.volumetrics->oversampling);
+			FRED_ENSURE_PROPERTY_VERSION_WITH_DEFAULT("+Smoothing:", 1, ";;FSO 25.0.0;;", 0.f, " %f", The_mission.volumetrics->smoothing);
 			FRED_ENSURE_PROPERTY_VERSION_WITH_DEFAULT_F("+Heyney Greenstein Coefficient:", 1, ";;FSO 23.1.0;;", 0.2f, " %f", The_mission.volumetrics->henyeyGreensteinCoeff);
 			FRED_ENSURE_PROPERTY_VERSION_WITH_DEFAULT_F("+Sun Falloff Factor:", 1, ";;FSO 23.1.0;;", 1.0f, " %f", The_mission.volumetrics->globalLightDistanceFactor);
 			FRED_ENSURE_PROPERTY_VERSION_WITH_DEFAULT("+Sun Steps:", 1, ";;FSO 23.1.0;;", 6, " %d", The_mission.volumetrics->globalLightSteps);
@@ -2721,6 +2722,7 @@ int CFred_mission_save::save_mission_info()
 			bypass_comment(";;FSO 23.1.0;; +Steps:");
 			bypass_comment(";;FSO 23.1.0;; +Resolution:");
 			bypass_comment(";;FSO 23.1.0;; +Oversampling:");
+			bypass_comment(";;FSO 25.0.0;; +Smoothing:");
 			bypass_comment(";;FSO 23.1.0;; +Heyney Greenstein Coefficient:");
 			bypass_comment(";;FSO 23.1.0;; +Sun Falloff Factor:");
 			bypass_comment(";;FSO 23.1.0;; +Sun Steps:");