Implement shadow meshes

-When importing, a vertex-only version of the mesh is created.
-This version is used when rendering shadows, and improves performance by reducing bandwidth
-It's automatic, but can optionally be used by users, in case they want to make special versions of geometry for shadow casting.

editor/import/resource_importer_scene.cpp

@@ -1129,6 +1129,7 @@ void ResourceImporterScene::get_import_options(List<ImportOption> *r_options, in
 	r_options->push_back(ImportOption(PropertyInfo(Variant::BOOL, "meshes/ensure_tangents"), true));
 	r_options->push_back(ImportOption(PropertyInfo(Variant::INT, "meshes/storage", PROPERTY_HINT_ENUM, "Built-In,Files (.mesh),Files (.tres)"), meshes_out ? 1 : 0));
 	r_options->push_back(ImportOption(PropertyInfo(Variant::BOOL, "meshes/generate_lods"), true));
+	r_options->push_back(ImportOption(PropertyInfo(Variant::BOOL, "meshes/create_shadow_meshes"), true));
 	r_options->push_back(ImportOption(PropertyInfo(Variant::INT, "meshes/light_baking", PROPERTY_HINT_ENUM, "Disabled,Enable,Gen Lightmaps", PROPERTY_USAGE_DEFAULT | PROPERTY_USAGE_UPDATE_ALL_IF_MODIFIED), 0));
 	r_options->push_back(ImportOption(PropertyInfo(Variant::FLOAT, "meshes/lightmap_texel_size", PROPERTY_HINT_RANGE, "0.001,100,0.001"), 0.1));
 	r_options->push_back(ImportOption(PropertyInfo(Variant::BOOL, "skins/use_named_skins"), true));
@@ -1221,7 +1222,7 @@ Ref<Animation> ResourceImporterScene::import_animation_from_other_importer(Edito
 	return importer->import_animation(p_path, p_flags, p_bake_fps);
 }
 
-void ResourceImporterScene::_generate_meshes(Node *p_node, bool p_generate_lods) {
+void ResourceImporterScene::_generate_meshes(Node *p_node, bool p_generate_lods, bool p_create_shadow_meshes) {
 	EditorSceneImporterMeshNode3D *src_mesh_node = Object::cast_to<EditorSceneImporterMeshNode3D>(p_node);
 	if (src_mesh_node) {
 		//is mesh
@@ -1237,8 +1238,12 @@ void ResourceImporterScene::_generate_meshes(Node *p_node, bool p_generate_lods)
 				if (p_generate_lods) {
 					src_mesh_node->get_mesh()->generate_lods();
 				}
+				if (p_create_shadow_meshes) {
+					src_mesh_node->get_mesh()->create_shadow_mesh();
+				}
 			}
 			mesh = src_mesh_node->get_mesh()->get_mesh();
+
 			if (mesh.is_valid()) {
 				mesh_node->set_mesh(mesh);
 				for (int i = 0; i < mesh->get_surface_count(); i++) {
@@ -1252,7 +1257,7 @@ void ResourceImporterScene::_generate_meshes(Node *p_node, bool p_generate_lods)
 	}
 
 	for (int i = 0; i < p_node->get_child_count(); i++) {
-		_generate_meshes(p_node->get_child(i), p_generate_lods);
+		_generate_meshes(p_node->get_child(i), p_generate_lods, p_create_shadow_meshes);
 	}
 }
 Error ResourceImporterScene::import(const String &p_source_file, const String &p_save_path, const Map<StringName, Variant> &p_options, List<String> *r_platform_variants, List<String> *r_gen_files, Variant *r_metadata) {
@@ -1348,8 +1353,9 @@ Error ResourceImporterScene::import(const String &p_source_file, const String &p
 	}
 
 	bool gen_lods = bool(p_options["meshes/generate_lods"]);
+	bool create_shadow_meshes = bool(p_options["meshes/create_shadow_meshes"]);
 
-	_generate_meshes(scene, gen_lods);
+	_generate_meshes(scene, gen_lods, create_shadow_meshes);
 
 	err = OK;
 

editor/import/resource_importer_scene.h

@@ -121,7 +121,7 @@ class ResourceImporterScene : public ResourceImporter {
 	};
 
 	void _replace_owner(Node *p_node, Node *p_scene, Node *p_new_owner);
-	void _generate_meshes(Node *p_node, bool p_generate_lods);
+	void _generate_meshes(Node *p_node, bool p_generate_lods, bool p_create_shadow_meshes);
 
 public:
 	static ResourceImporterScene *get_singleton() { return singleton; }

editor/import/scene_importer_mesh.cpp

@@ -250,6 +250,11 @@ Ref<ArrayMesh> EditorSceneImporterMesh::get_mesh() {
 				mesh->surface_set_name(mesh->get_surface_count() - 1, surfaces[i].name);
 			}
 		}
+
+		if (shadow_mesh.is_valid()) {
+			Ref<ArrayMesh> shadow = shadow_mesh->get_mesh();
+			mesh->set_shadow_mesh(shadow);
+		}
 	}
 
 	return mesh;
@@ -261,6 +266,103 @@ void EditorSceneImporterMesh::clear() {
 	mesh.unref();
 }
 
+void EditorSceneImporterMesh::create_shadow_mesh() {
+	if (shadow_mesh.is_valid()) {
+		shadow_mesh.unref();
+	}
+
+	//no shadow mesh for blendshapes
+	if (blend_shapes.size() > 0) {
+		return;
+	}
+	//no shadow mesh for skeletons
+	for (int i = 0; i < surfaces.size(); i++) {
+		if (surfaces[i].arrays[RS::ARRAY_BONES].get_type() != Variant::NIL) {
+			return;
+		}
+		if (surfaces[i].arrays[RS::ARRAY_WEIGHTS].get_type() != Variant::NIL) {
+			return;
+		}
+	}
+
+	shadow_mesh.instance();
+
+	for (int i = 0; i < surfaces.size(); i++) {
+		LocalVector<int> vertex_remap;
+		Vector<Vector3> new_vertices;
+		Vector<Vector3> vertices = surfaces[i].arrays[RS::ARRAY_VERTEX];
+		int vertex_count = vertices.size();
+		{
+			Map<Vector3, int> unique_vertices;
+			const Vector3 *vptr = vertices.ptr();
+			for (int j = 0; j < vertex_count; j++) {
+				Vector3 v = vptr[j];
+
+				Map<Vector3, int>::Element *E = unique_vertices.find(v);
+
+				if (E) {
+					vertex_remap.push_back(E->get());
+				} else {
+					int vcount = unique_vertices.size();
+					unique_vertices[v] = vcount;
+					vertex_remap.push_back(vcount);
+					new_vertices.push_back(v);
+				}
+			}
+		}
+
+		Array new_surface;
+		new_surface.resize(RS::ARRAY_MAX);
+		Dictionary lods;
+
+		//		print_line("original vertex count: " + itos(vertices.size()) + " new vertex count: " + itos(new_vertices.size()));
+
+		new_surface[RS::ARRAY_VERTEX] = new_vertices;
+
+		Vector<int> indices = surfaces[i].arrays[RS::ARRAY_INDEX];
+		if (indices.size()) {
+			int index_count = indices.size();
+			const int *index_rptr = indices.ptr();
+			Vector<int> new_indices;
+			new_indices.resize(indices.size());
+			int *index_wptr = new_indices.ptrw();
+
+			for (int j = 0; j < index_count; j++) {
+				int index = index_rptr[j];
+				ERR_FAIL_INDEX(index, vertex_count);
+				index_wptr[j] = vertex_remap[index];
+			}
+
+			new_surface[RS::ARRAY_INDEX] = new_indices;
+
+			// Make sure the same LODs as the full version are used.
+			// This makes it more coherent between rendered model and its shadows.
+			for (int j = 0; j < surfaces[i].lods.size(); j++) {
+				indices = surfaces[i].lods[j].indices;
+
+				index_count = indices.size();
+				index_rptr = indices.ptr();
+				new_indices.resize(indices.size());
+				index_wptr = new_indices.ptrw();
+
+				for (int k = 0; k < index_count; k++) {
+					int index = index_rptr[j];
+					ERR_FAIL_INDEX(index, vertex_count);
+					index_wptr[j] = vertex_remap[index];
+				}
+
+				lods[surfaces[i].lods[j].distance] = new_indices;
+			}
+		}
+
+		shadow_mesh->add_surface(surfaces[i].primitive, new_surface, Array(), lods, Ref<Material>(), surfaces[i].name);
+	}
+}
+
+Ref<EditorSceneImporterMesh> EditorSceneImporterMesh::get_shadow_mesh() const {
+	return shadow_mesh;
+}
+
 void EditorSceneImporterMesh::_set_data(const Dictionary &p_data) {
 	clear();
 	if (p_data.has("blend_shape_names")) {

editor/import/scene_importer_mesh.h

@@ -61,6 +61,8 @@ class EditorSceneImporterMesh : public Resource {
 
 	Ref<ArrayMesh> mesh;
 
+	Ref<EditorSceneImporterMesh> shadow_mesh;
+
 protected:
 	void _set_data(const Dictionary &p_data);
 	Dictionary _get_data() const;
@@ -89,6 +91,9 @@ class EditorSceneImporterMesh : public Resource {
 
 	void generate_lods();
 
+	void create_shadow_mesh();
+	Ref<EditorSceneImporterMesh> get_shadow_mesh() const;
+
 	bool has_mesh() const;
 	Ref<ArrayMesh> get_mesh();
 	void clear();

scene/resources/mesh.cpp

@@ -1565,6 +1565,19 @@ Error ArrayMesh::lightmap_unwrap_cached(int *&r_cache_data, unsigned int &r_cach
 	return OK;
 }
 
+void ArrayMesh::set_shadow_mesh(const Ref<ArrayMesh> &p_mesh) {
+	shadow_mesh = p_mesh;
+	if (shadow_mesh.is_valid()) {
+		RS::get_singleton()->mesh_set_shadow_mesh(mesh, shadow_mesh->get_rid());
+	} else {
+		RS::get_singleton()->mesh_set_shadow_mesh(mesh, RID());
+	}
+}
+
+Ref<ArrayMesh> ArrayMesh::get_shadow_mesh() const {
+	return shadow_mesh;
+}
+
 void ArrayMesh::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("add_blend_shape", "name"), &ArrayMesh::add_blend_shape);
 	ClassDB::bind_method(D_METHOD("get_blend_shape_count"), &ArrayMesh::get_blend_shape_count);
@@ -1596,6 +1609,9 @@ void ArrayMesh::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_custom_aabb", "aabb"), &ArrayMesh::set_custom_aabb);
 	ClassDB::bind_method(D_METHOD("get_custom_aabb"), &ArrayMesh::get_custom_aabb);
 
+	ClassDB::bind_method(D_METHOD("set_shadow_mesh", "mesh"), &ArrayMesh::set_shadow_mesh);
+	ClassDB::bind_method(D_METHOD("get_shadow_mesh"), &ArrayMesh::get_shadow_mesh);
+
 	ClassDB::bind_method(D_METHOD("_set_blend_shape_names", "blend_shape_names"), &ArrayMesh::_set_blend_shape_names);
 	ClassDB::bind_method(D_METHOD("_get_blend_shape_names"), &ArrayMesh::_get_blend_shape_names);
 
@@ -1606,6 +1622,7 @@ void ArrayMesh::_bind_methods() {
 	ADD_PROPERTY(PropertyInfo(Variant::ARRAY, "_surfaces", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_NOEDITOR | PROPERTY_USAGE_INTERNAL), "_set_surfaces", "_get_surfaces");
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "blend_shape_mode", PROPERTY_HINT_ENUM, "Normalized,Relative"), "set_blend_shape_mode", "get_blend_shape_mode");
 	ADD_PROPERTY(PropertyInfo(Variant::AABB, "custom_aabb", PROPERTY_HINT_NONE, ""), "set_custom_aabb", "get_custom_aabb");
+	ADD_PROPERTY(PropertyInfo(Variant::OBJECT, "shadow_mesh", PROPERTY_HINT_RESOURCE_TYPE, "ArrayMesh"), "set_shadow_mesh", "get_shadow_mesh");
 }
 
 void ArrayMesh::reload_from_file() {

scene/resources/mesh.h

@@ -176,6 +176,7 @@ class ArrayMesh : public Mesh {
 
 	Array _get_surfaces() const;
 	void _set_surfaces(const Array &p_data);
+	Ref<ArrayMesh> shadow_mesh;
 
 private:
 	struct Surface {
@@ -259,6 +260,9 @@ class ArrayMesh : public Mesh {
 
 	virtual void reload_from_file() override;
 
+	void set_shadow_mesh(const Ref<ArrayMesh> &p_mesh);
+	Ref<ArrayMesh> get_shadow_mesh() const;
+
 	ArrayMesh();
 
 	~ArrayMesh();

servers/rendering/renderer_rd/renderer_scene_render_forward.cpp

@@ -819,7 +819,7 @@ void RendererSceneRenderForward::_render_list_template(RenderingDevice::DrawList
 		ShaderData *shader;
 		void *mesh_surface;
 
-		if (shadow_pass) {
+		if (shadow_pass || p_params->pass_mode == PASS_MODE_DEPTH) { //regular depth pass can use these too
 			material_uniform_set = surf->material_uniform_set_shadow;
 			shader = surf->shader_shadow;
 			mesh_surface = surf->surface_shadow;
@@ -2645,10 +2645,17 @@ void RendererSceneRenderForward::_geometry_instance_add_surface_with_material(Ge
 	}
 
 	MaterialData *material_shadow = nullptr;
-	//void *surface_shadow = nullptr;
+	void *surface_shadow = nullptr;
 	if (!p_material->shader_data->writes_modelview_or_projection && !p_material->shader_data->uses_vertex && !p_material->shader_data->uses_discard && !p_material->shader_data->uses_depth_pre_pass) {
 		flags |= GeometryInstanceSurfaceDataCache::FLAG_USES_SHARED_SHADOW_MATERIAL;
 		material_shadow = (MaterialData *)storage->material_get_data(default_material, RendererStorageRD::SHADER_TYPE_3D);
+
+		RID shadow_mesh = storage->mesh_get_shadow_mesh(p_mesh);
+
+		if (shadow_mesh.is_valid()) {
+			surface_shadow = storage->mesh_get_surface(shadow_mesh, p_surface);
+		}
+
 	} else {
 		material_shadow = p_material;
 	}
@@ -2670,7 +2677,8 @@ void RendererSceneRenderForward::_geometry_instance_add_surface_with_material(Ge
 	//shadow
 	sdcache->shader_shadow = material_shadow->shader_data;
 	sdcache->material_uniform_set_shadow = material_shadow->uniform_set;
-	sdcache->surface_shadow = sdcache->surface; //when adding special shadow meshes, will use this
+
+	sdcache->surface_shadow = surface_shadow ? surface_shadow : sdcache->surface;
 
 	sdcache->owner = ginstance;
 

servers/rendering/renderer_rd/renderer_storage_rd.cpp

@@ -2609,6 +2609,12 @@ void RendererStorageRD::mesh_add_surface(RID p_mesh, const RS::SurfaceData &p_su
 
 	mesh->dependency.changed_notify(DEPENDENCY_CHANGED_MESH);
 
+	for (Set<Mesh *>::Element *E = mesh->shadow_owners.front(); E; E = E->next()) {
+		Mesh *shadow_owner = E->get();
+		shadow_owner->shadow_mesh = RID();
+		shadow_owner->dependency.changed_notify(DEPENDENCY_CHANGED_MESH);
+	}
+
 	mesh->material_cache.clear();
 }
 
@@ -2824,6 +2830,25 @@ AABB RendererStorageRD::mesh_get_aabb(RID p_mesh, RID p_skeleton) {
 	return aabb;
 }
 
+void RendererStorageRD::mesh_set_shadow_mesh(RID p_mesh, RID p_shadow_mesh) {
+	Mesh *mesh = mesh_owner.getornull(p_mesh);
+	ERR_FAIL_COND(!mesh);
+
+	Mesh *shadow_mesh = mesh_owner.getornull(mesh->shadow_mesh);
+	if (shadow_mesh) {
+		shadow_mesh->shadow_owners.erase(mesh);
+	}
+	mesh->shadow_mesh = p_shadow_mesh;
+
+	shadow_mesh = mesh_owner.getornull(mesh->shadow_mesh);
+
+	if (shadow_mesh) {
+		shadow_mesh->shadow_owners.insert(mesh);
+	}
+
+	mesh->dependency.changed_notify(DEPENDENCY_CHANGED_MESH);
+}
+
 void RendererStorageRD::mesh_clear(RID p_mesh) {
 	Mesh *mesh = mesh_owner.getornull(p_mesh);
 	ERR_FAIL_COND(!mesh);
@@ -2871,6 +2896,12 @@ void RendererStorageRD::mesh_clear(RID p_mesh) {
 	}
 	mesh->has_bone_weights = false;
 	mesh->dependency.changed_notify(DEPENDENCY_CHANGED_MESH);
+
+	for (Set<Mesh *>::Element *E = mesh->shadow_owners.front(); E; E = E->next()) {
+		Mesh *shadow_owner = E->get();
+		shadow_owner->shadow_mesh = RID();
+		shadow_owner->dependency.changed_notify(DEPENDENCY_CHANGED_MESH);
+	}
 }
 
 bool RendererStorageRD::mesh_needs_instance(RID p_mesh, bool p_has_skeleton) {
@@ -8161,17 +8192,26 @@ bool RendererStorageRD::free(RID p_rid) {
 		material_owner.free(p_rid);
 	} else if (mesh_owner.owns(p_rid)) {
 		mesh_clear(p_rid);
+		mesh_set_shadow_mesh(p_rid, RID());
 		Mesh *mesh = mesh_owner.getornull(p_rid);
 		mesh->dependency.deleted_notify(p_rid);
 		if (mesh->instances.size()) {
 			ERR_PRINT("deleting mesh with active instances");
 		}
+		if (mesh->shadow_owners.size()) {
+			for (Set<Mesh *>::Element *E = mesh->shadow_owners.front(); E; E = E->next()) {
+				Mesh *shadow_owner = E->get();
+				shadow_owner->shadow_mesh = RID();
+				shadow_owner->dependency.changed_notify(DEPENDENCY_CHANGED_MESH);
+			}
+		}
 		mesh_owner.free(p_rid);
 	} else if (mesh_instance_owner.owns(p_rid)) {
 		MeshInstance *mi = mesh_instance_owner.getornull(p_rid);
 		_mesh_instance_clear(mi);
 		mi->mesh->instances.erase(mi->I);
 		mi->I = nullptr;
+
 		mesh_instance_owner.free(p_rid);
 		memdelete(mi);
 

servers/rendering/renderer_rd/renderer_storage_rd.h

@@ -478,6 +478,9 @@ class RendererStorageRD : public RendererStorage {
 
 		List<MeshInstance *> instances;
 
+		RID shadow_mesh;
+		Set<Mesh *> shadow_owners;
+
 		Dependency dependency;
 	};
 
@@ -1423,6 +1426,7 @@ class RendererStorageRD : public RendererStorage {
 	virtual AABB mesh_get_custom_aabb(RID p_mesh) const;
 
 	virtual AABB mesh_get_aabb(RID p_mesh, RID p_skeleton = RID());
+	virtual void mesh_set_shadow_mesh(RID p_mesh, RID p_shadow_mesh);
 
 	virtual void mesh_clear(RID p_mesh);
 
@@ -1461,6 +1465,13 @@ class RendererStorageRD : public RendererStorage {
 		return mesh->surfaces[p_surface_index];
 	}
 
+	_FORCE_INLINE_ RID mesh_get_shadow_mesh(RID p_mesh) {
+		Mesh *mesh = mesh_owner.getornull(p_mesh);
+		ERR_FAIL_COND_V(!mesh, RID());
+
+		return mesh->shadow_mesh;
+	}
+
 	_FORCE_INLINE_ RS::PrimitiveType mesh_surface_get_primitive(void *p_surface) {
 		Mesh::Surface *surface = reinterpret_cast<Mesh::Surface *>(p_surface);
 		return surface->primitive;