Updated lightmap baker to dynamically calculate lightmap sizes based on surface area.

scene/3d/baked_lightmap.cpp

@@ -221,6 +221,15 @@ Vector3 BakedLightmap::get_extents() const {
 	return extents;
 }
 
+void BakedLightmap::set_bake_default_texels_per_unit(const float &p_bake_texels_per_unit) {
+	bake_default_texels_per_unit = p_bake_texels_per_unit;
+	update_gizmo();
+}
+
+float BakedLightmap::get_bake_default_texels_per_unit() const {
+	return bake_default_texels_per_unit;
+}
+
 void BakedLightmap::_find_meshes_and_lights(Node *p_at_node, List<PlotMesh> &plot_meshes, List<PlotLight> &plot_lights) {
 
 	MeshInstance *mi = Object::cast_to<MeshInstance>(p_at_node);
@@ -236,7 +245,7 @@ void BakedLightmap::_find_meshes_and_lights(Node *p_at_node, List<PlotMesh> &plo
 				}
 			}
 
-			if (all_have_uv2 && mesh->get_lightmap_size_hint() != Size2()) {
+			if (all_have_uv2) {
 				//READY TO BAKE! size hint could be computed if not found, actually..
 
 				AABB aabb = mesh->get_aabb();
@@ -463,7 +472,7 @@ BakedLightmap::BakeError BakedLightmap::bake(Node *p_from_node, bool p_create_vi
 			btd.text = RTR("Lighting Meshes: ") + mesh_name + " (" + itos(pmc) + "/" + itos(mesh_list.size()) + ")";
 			btd.pass = step;
 			btd.last_step = 0;
-			err = baker.make_lightmap(E->get().local_xform, E->get().mesh, lm, _bake_time, &btd);
+			err = baker.make_lightmap(E->get().local_xform, E->get().mesh, bake_default_texels_per_unit, lm, _bake_time, &btd);
 			if (err != OK) {
 				bake_end_function();
 				if (err == ERR_SKIP)
@@ -473,7 +482,7 @@ BakedLightmap::BakeError BakedLightmap::bake(Node *p_from_node, bool p_create_vi
 			step += 100;
 		} else {
 
-			err = baker.make_lightmap(E->get().local_xform, E->get().mesh, lm);
+			err = baker.make_lightmap(E->get().local_xform, E->get().mesh, bake_default_texels_per_unit, lm);
 		}
 
 		if (err == OK) {
@@ -790,6 +799,9 @@ void BakedLightmap::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_extents", "extents"), &BakedLightmap::set_extents);
 	ClassDB::bind_method(D_METHOD("get_extents"), &BakedLightmap::get_extents);
 
+	ClassDB::bind_method(D_METHOD("set_bake_default_texels_per_unit", "texels"), &BakedLightmap::set_bake_default_texels_per_unit);
+	ClassDB::bind_method(D_METHOD("get_bake_default_texels_per_unit"), &BakedLightmap::get_bake_default_texels_per_unit);
+
 	ClassDB::bind_method(D_METHOD("set_propagation", "propagation"), &BakedLightmap::set_propagation);
 	ClassDB::bind_method(D_METHOD("get_propagation"), &BakedLightmap::get_propagation);
 
@@ -814,6 +826,7 @@ void BakedLightmap::_bind_methods() {
 	ADD_PROPERTY(PropertyInfo(Variant::REAL, "bake_energy", PROPERTY_HINT_RANGE, "0,32,0.01"), "set_energy", "get_energy");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "bake_hdr"), "set_hdr", "is_hdr");
 	ADD_PROPERTY(PropertyInfo(Variant::VECTOR3, "bake_extents"), "set_extents", "get_extents");
+	ADD_PROPERTY(PropertyInfo(Variant::REAL, "bake_default_texels_per_unit"), "set_bake_default_texels_per_unit", "get_bake_default_texels_per_unit");
 	ADD_GROUP("Capture", "capture_");
 	ADD_PROPERTY(PropertyInfo(Variant::REAL, "capture_cell_size", PROPERTY_HINT_RANGE, "0.01,64,0.01"), "set_capture_cell_size", "get_capture_cell_size");
 	ADD_GROUP("Data", "");
@@ -836,6 +849,7 @@ void BakedLightmap::_bind_methods() {
 BakedLightmap::BakedLightmap() {
 
 	extents = Vector3(10, 10, 10);
+	bake_default_texels_per_unit = 20;
 	bake_cell_size = 0.25;
 	capture_cell_size = 0.5;
 

scene/3d/baked_lightmap.h

@@ -119,6 +119,7 @@ private:
 	float bake_cell_size;
 	float capture_cell_size;
 	Vector3 extents;
+	float bake_default_texels_per_unit;
 	float propagation;
 	float energy;
 	BakeQuality bake_quality;
@@ -178,6 +179,9 @@ public:
 	void set_extents(const Vector3 &p_extents);
 	Vector3 get_extents() const;
 
+	void set_bake_default_texels_per_unit(const float &p_extents);
+	float get_bake_default_texels_per_unit() const;
+
 	void set_propagation(float p_propagation);
 	float get_propagation() const;
 

scene/3d/voxel_light_baker.cpp

@@ -1794,19 +1794,82 @@ void VoxelLightBaker::_lightmap_bake_point(uint32_t p_x, LightMap *p_line) {
 	}
 }
 
-Error VoxelLightBaker::make_lightmap(const Transform &p_xform, Ref<Mesh> &p_mesh, LightMapData &r_lightmap, bool (*p_bake_time_func)(void *, float, float), void *p_bake_time_ud) {
+Error VoxelLightBaker::make_lightmap(const Transform &p_xform, Ref<Mesh> &p_mesh, float default_texels_per_unit, LightMapData &r_lightmap, bool (*p_bake_time_func)(void *, float, float), void *p_bake_time_ud) {
 
 	//transfer light information to a lightmap
 	Ref<Mesh> mesh = p_mesh;
 
-	int width = mesh->get_lightmap_size_hint().x;
-	int height = mesh->get_lightmap_size_hint().y;
-
 	//step 1 - create lightmap
+	int width;
+	int height;
 	Vector<LightMap> lightmap;
-	lightmap.resize(width * height);
-
 	Transform xform = to_cell_space * p_xform;
+	if (mesh->get_lightmap_size_hint() == Size2()) {
+		double area = 0;
+		double uv_area = 0;
+		for (int i = 0; i < mesh->get_surface_count(); i++) {
+			Array arrays = mesh->surface_get_arrays(i);
+			PoolVector<Vector3> vertices = arrays[Mesh::ARRAY_VERTEX];
+			PoolVector<Vector2> uv2 = arrays[Mesh::ARRAY_TEX_UV2];
+			PoolVector<int> indices = arrays[Mesh::ARRAY_INDEX];
+
+			ERR_FAIL_COND_V(vertices.size() == 0, ERR_INVALID_PARAMETER);
+			ERR_FAIL_COND_V(uv2.size() == 0, ERR_INVALID_PARAMETER);
+
+			int vc = vertices.size();
+			PoolVector<Vector3>::Read vr = vertices.read();
+			PoolVector<Vector2>::Read u2r = uv2.read();
+			PoolVector<int>::Read ir;
+			int ic = 0;
+
+			if (indices.size()) {
+				ic = indices.size();
+				ir = indices.read();
+			}
+
+			int faces = ic ? ic / 3 : vc / 3;
+			for (int j = 0; j < faces; j++) {
+				Vector3 vertex[3];
+				Vector2 uv[3];
+
+				for (int k = 0; k < 3; k++) {
+					int idx = ic ? ir[j * 3 + k] : j * 3 + k;
+					vertex[k] = xform.xform(vr[idx]);
+					uv[k] = u2r[idx];
+				}
+
+				Vector3 p1 = vertex[0];
+				Vector3 p2 = vertex[1];
+				Vector3 p3 = vertex[2];
+				double a = p1.distance_to(p2);
+				double b = p2.distance_to(p3);
+				double c = p3.distance_to(p1);
+				double halfPerimeter = (a + b + c) / 2.0;
+				area += sqrt(halfPerimeter * (halfPerimeter - a) * (halfPerimeter - b) * (halfPerimeter - c));
+
+				Vector2 uv_p1 = uv[0];
+				Vector2 uv_p2 = uv[1];
+				Vector2 uv_p3 = uv[2];
+				double uv_a = uv_p1.distance_to(uv_p2);
+				double uv_b = uv_p2.distance_to(uv_p3);
+				double uv_c = uv_p3.distance_to(uv_p1);
+				double uv_halfPerimeter = (uv_a + uv_b + uv_c) / 2.0;
+				uv_area += sqrt(uv_halfPerimeter * (uv_halfPerimeter - uv_a) * (uv_halfPerimeter - uv_b) * (uv_halfPerimeter - uv_c));
+			}
+		}
+
+		if (uv_area < 0.0001f) {
+			uv_area = 1.0;
+		}
+
+		int pixels = (ceil((1.0 / sqrt(uv_area)) * sqrt(area * default_texels_per_unit)));
+		width = height = CLAMP(pixels, 2, 4096);
+	} else {
+		width = mesh->get_lightmap_size_hint().x;
+		height = mesh->get_lightmap_size_hint().y;
+	}
+
+	lightmap.resize(width * height);
 
 	//step 2 plot faces to lightmap
 	for (int i = 0; i < mesh->get_surface_count(); i++) {

scene/3d/voxel_light_baker.h

@@ -177,7 +177,7 @@ public:
 		PoolVector<float> light;
 	};
 
-	Error make_lightmap(const Transform &p_xform, Ref<Mesh> &p_mesh, LightMapData &r_lightmap, bool (*p_bake_time_func)(void *, float, float) = NULL, void *p_bake_time_ud = NULL);
+	Error make_lightmap(const Transform &p_xform, Ref<Mesh> &p_mesh, float default_texels_per_unit, LightMapData &r_lightmap, bool (*p_bake_time_func)(void *, float, float) = NULL, void *p_bake_time_ud = NULL);
 
 	PoolVector<int> create_gi_probe_data();
 	Ref<MultiMesh> create_debug_multimesh(DebugMode p_mode = DEBUG_ALBEDO);