Fix node-nodebox lighting difference in direct sunlight (#7061)

src/content_mapblock.cpp

@@ -151,7 +151,7 @@ void MapblockMeshGenerator::drawQuad(v3f *coords, const v3s16 &normal,
 //              the faces in the list is up-down-right-left-back-front
 //              (compatible with ContentFeatures).
 void MapblockMeshGenerator::drawCuboid(const aabb3f &box,
-	TileSpec *tiles, int tilecount, const LightPair *lights, const f32 *txc)
+	TileSpec *tiles, int tilecount, const LightInfo *lights, const f32 *txc)
 {
 	assert(tilecount >= 1 && tilecount <= 6); // pre-condition
 
@@ -263,10 +263,12 @@ void MapblockMeshGenerator::drawCuboid(const aabb3f &box,
 
 	if (data->m_smooth_lighting) {
 		for (int j = 0; j < 24; ++j) {
-			vertices[j].Color = encode_light(lights[light_indices[j]],
+			video::S3DVertex &vertex = vertices[j];
+			vertex.Color = encode_light(
+				lights[light_indices[j]].getPair(MYMAX(0.0f, vertex.Normal.Y)),
 				f->light_source);
 			if (!f->light_source)
-				applyFacesShading(vertices[j].Color, vertices[j].Normal);
+				applyFacesShading(vertex.Color, vertex.Normal);
 		}
 	}
 
@@ -280,45 +282,61 @@ void MapblockMeshGenerator::drawCuboid(const aabb3f &box,
 // Gets the base lighting values for a node
 void MapblockMeshGenerator::getSmoothLightFrame()
 {
+	for (int k = 0; k < 8; ++k)
+		frame.sunlight[k] = false;
 	for (int k = 0; k < 8; ++k) {
 		LightPair light(getSmoothLightTransparent(blockpos_nodes + p, light_dirs[k], data));
-		frame.lightsA[k] = light.lightA;
-		frame.lightsB[k] = light.lightB;
+		frame.lightsDay[k] = light.lightDay;
+		frame.lightsNight[k] = light.lightNight;
+		// If there is direct sunlight and no ambient occlusion at some corner,
+		// mark the vertical edge (top and bottom corners) containing it.
+		if (light.lightDay == 255) {
+			frame.sunlight[k] = true;
+			frame.sunlight[k ^ 2] = true;
+		}
 	}
 }
 
 // Calculates vertex light level
 //  vertex_pos - vertex position in the node (coordinates are clamped to [0.0, 1.0] or so)
-LightPair MapblockMeshGenerator::blendLight(const v3f &vertex_pos)
+LightInfo MapblockMeshGenerator::blendLight(const v3f &vertex_pos)
 {
+	// Light levels at (logical) node corners are known. Here,
+	// trilinear interpolation is used to calculate light level
+	// at a given point in the node.
 	f32 x = core::clamp(vertex_pos.X / BS + 0.5, 0.0 - SMOOTH_LIGHTING_OVERSIZE, 1.0 + SMOOTH_LIGHTING_OVERSIZE);
 	f32 y = core::clamp(vertex_pos.Y / BS + 0.5, 0.0 - SMOOTH_LIGHTING_OVERSIZE, 1.0 + SMOOTH_LIGHTING_OVERSIZE);
 	f32 z = core::clamp(vertex_pos.Z / BS + 0.5, 0.0 - SMOOTH_LIGHTING_OVERSIZE, 1.0 + SMOOTH_LIGHTING_OVERSIZE);
-	f32 lightA = 0.0;
-	f32 lightB = 0.0;
+	f32 lightDay = 0.0; // daylight
+	f32 lightNight = 0.0;
+	f32 lightBoosted = 0.0; // daylight + direct sunlight, if any
 	for (int k = 0; k < 8; ++k) {
 		f32 dx = (k & 4) ? x : 1 - x;
 		f32 dy = (k & 2) ? y : 1 - y;
 		f32 dz = (k & 1) ? z : 1 - z;
-		lightA += dx * dy * dz * frame.lightsA[k];
-		lightB += dx * dy * dz * frame.lightsB[k];
+		// Use direct sunlight (255), if any; use daylight otherwise.
+		f32 light_boosted = frame.sunlight[k] ? 255 : frame.lightsDay[k];
+		lightDay += dx * dy * dz * frame.lightsDay[k];
+		lightNight += dx * dy * dz * frame.lightsNight[k];
+		lightBoosted += dx * dy * dz * light_boosted;
 	}
-	return LightPair(lightA, lightB);
+	return LightInfo{lightDay, lightNight, lightBoosted};
 }
 
 // Calculates vertex color to be used in mapblock mesh
 //  vertex_pos - vertex position in the node (coordinates are clamped to [0.0, 1.0] or so)
 //  tile_color - node's tile color
 video::SColor MapblockMeshGenerator::blendLightColor(const v3f &vertex_pos)
 {
-	LightPair light = blendLight(vertex_pos);
-	return encode_light(light, f->light_source);
+	LightInfo light = blendLight(vertex_pos);
+	return encode_light(light.getPair(), f->light_source);
 }
 
 video::SColor MapblockMeshGenerator::blendLightColor(const v3f &vertex_pos,
 	const v3f &vertex_normal)
 {
-	video::SColor color = blendLightColor(vertex_pos);
+	LightInfo light = blendLight(vertex_pos);
+	video::SColor color = encode_light(light.getPair(MYMAX(0.0f, vertex_normal.Y)), f->light_source);
 	if (!f->light_source)
 		applyFacesShading(color, vertex_normal);
 	return color;
@@ -365,7 +383,7 @@ void MapblockMeshGenerator::drawAutoLightedCuboid(aabb3f box, const f32 *txc,
 		tile_count = 1;
 	}
 	if (data->m_smooth_lighting) {
-		LightPair lights[8];
+		LightInfo lights[8];
 		for (int j = 0; j < 8; ++j) {
 			v3f d;
 			d.X = (j & 4) ? dx2 : dx1;
@@ -403,7 +421,7 @@ void MapblockMeshGenerator::prepareLiquidNodeDrawing()
 		// If this liquid emits light and doesn't contain light, draw
 		// it at what it emits, for an increased effect
 		u8 e = decode_light(f->light_source);
-		light = LightPair(std::max(e, light.lightA), std::max(e, light.lightB));
+		light = LightPair(std::max(e, light.lightDay), std::max(e, light.lightNight));
 	} else if (nodedef->get(ntop).param_type == CPT_LIGHT) {
 		// Otherwise, use the light of the node on top if possible
 		light = LightPair(getInteriorLight(ntop, 0, nodedef));

src/content_mapblock.h

@@ -26,21 +26,36 @@ struct MeshMakeData;
 struct MeshCollector;
 
 struct LightPair {
-	u8 lightA;
-	u8 lightB;
+	u8 lightDay;
+	u8 lightNight;
 
 	LightPair() = default;
-	explicit LightPair(u16 value) : lightA(value & 0xff), lightB(value >> 8) {}
-	LightPair(u8 valueA, u8 valueB) : lightA(valueA), lightB(valueB) {}
+	explicit LightPair(u16 value) : lightDay(value & 0xff), lightNight(value >> 8) {}
+	LightPair(u8 valueA, u8 valueB) : lightDay(valueA), lightNight(valueB) {}
 	LightPair(float valueA, float valueB) :
-		lightA(core::clamp(core::round32(valueA), 0, 255)),
-		lightB(core::clamp(core::round32(valueB), 0, 255)) {}
-	operator u16() const { return lightA | lightB << 8; }
+		lightDay(core::clamp(core::round32(valueA), 0, 255)),
+		lightNight(core::clamp(core::round32(valueB), 0, 255)) {}
+	operator u16() const { return lightDay | lightNight << 8; }
+};
+
+struct LightInfo {
+	float light_day;
+	float light_night;
+	float light_boosted;
+
+	LightPair getPair(float sunlight_boost = 0.0) const
+	{
+		return LightPair(
+			(1 - sunlight_boost) * light_day
+			+ sunlight_boost * light_boosted,
+			light_night);
+	}
 };
 
 struct LightFrame {
-	f32 lightsA[8];
-	f32 lightsB[8];
+	f32 lightsDay[8];
+	f32 lightsNight[8];
+	bool sunlight[8];
 };
 
 class MapblockMeshGenerator
@@ -69,7 +84,7 @@ class MapblockMeshGenerator
 
 // lighting
 	void getSmoothLightFrame();
-	LightPair blendLight(const v3f &vertex_pos);
+	LightInfo blendLight(const v3f &vertex_pos);
 	video::SColor blendLightColor(const v3f &vertex_pos);
 	video::SColor blendLightColor(const v3f &vertex_pos, const v3f &vertex_normal);
 
@@ -85,7 +100,7 @@ class MapblockMeshGenerator
 
 // cuboid drawing!
 	void drawCuboid(const aabb3f &box, TileSpec *tiles, int tilecount,
-		const LightPair *lights , const f32 *txc);
+		const LightInfo *lights , const f32 *txc);
 	void generateCuboidTextureCoords(aabb3f const &box, f32 *coords);
 	void drawAutoLightedCuboid(aabb3f box, const f32 *txc = NULL,
 		TileSpec *tiles = NULL, int tile_count = 0);

src/mapblock_mesh.cpp

@@ -196,6 +196,7 @@ static u16 getSmoothLightCombined(const v3s16 &p,
 	u8 light_source_max = 0;
 	u16 light_day = 0;
 	u16 light_night = 0;
+	bool direct_sunlight = false;
 
 	auto add_node = [&] (u8 i, bool obstructed = false) -> bool {
 		if (obstructed) {
@@ -210,8 +211,12 @@ static u16 getSmoothLightCombined(const v3s16 &p,
 			light_source_max = f.light_source;
 		// Check f.solidness because fast-style leaves look better this way
 		if (f.param_type == CPT_LIGHT && f.solidness != 2) {
-			light_day += decode_light(n.getLightNoChecks(LIGHTBANK_DAY, &f));
-			light_night += decode_light(n.getLightNoChecks(LIGHTBANK_NIGHT, &f));
+			u8 light_level_day = n.getLightNoChecks(LIGHTBANK_DAY, &f);
+			u8 light_level_night = n.getLightNoChecks(LIGHTBANK_NIGHT, &f);
+			if (light_level_day == LIGHT_SUN)
+				direct_sunlight = true;
+			light_day += decode_light(light_level_day);
+			light_night += decode_light(light_level_night);
 			light_count++;
 		} else {
 			ambient_occlusion++;
@@ -243,6 +248,10 @@ static u16 getSmoothLightCombined(const v3s16 &p,
 		light_night /= light_count;
 	}
 
+	// boost direct sunlight, if any
+	if (direct_sunlight)
+		light_day = 0xFF;
+
 	// Boost brightness around light sources
 	bool skip_ambient_occlusion_day = false;
 	if (decode_light(light_source_max) >= light_day) {