fyrox_impl/resource/model/

mod.rs

// Copyright (c) 2019-present Dmitry Stepanov and Fyrox Engine contributors.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

#![warn(missing_docs)]

//! Contains all data structures and method to work with model resources.
//!
//! Model is an isolated scene that is used to create copies of its data - this
//! process is known as `instantiation`. Isolation in this context means that
//! such scene cannot be modified, rendered, etc. It just a data source.
//!
//! All instances will have references to resource they were created from - this
//! will help to get correct vertex and indices buffers when loading a save file,
//! loader will just take all needed data from resource so we don't need to store
//! such data in save file. Also this mechanism works perfectly when you changing
//! resource in external editor (3Ds max, Maya, Blender, etc.) engine will assign
//! correct visual data when loading a saved game.
//!
//! # Supported formats
//!
//! Currently only FBX (common format in game industry for storing complex 3d models),
//! RGS (native Fyroxed format), GLTF formats are supported.

use crate::{
    asset::{
        io::ResourceIo, manager::ResourceManager, options::ImportOptions, untyped::ResourceKind,
        Resource, ResourceData, MODEL_RESOURCE_UUID,
    },
    core::{
        algebra::{UnitQuaternion, Vector3},
        log::{Log, MessageKind},
        pool::Handle,
        reflect::prelude::*,
        uuid::Uuid,
        uuid_provider,
        variable::InheritableVariable,
        visitor::{Visit, VisitResult, Visitor},
        NameProvider, TypeUuidProvider,
    },
    engine::SerializationContext,
    generic_animation::AnimationContainer,
    graph::{BaseSceneGraph, NodeHandleMap, NodeMapping, PrefabData, SceneGraph, SceneGraphNode},
    resource::fbx::{self, error::FbxError},
    scene::{
        animation::Animation, base::SceneNodeId, graph::Graph, node::Node, transform::Transform,
        Scene, SceneLoader,
    },
};
use fxhash::FxHashMap;
use fyrox_core::algebra::Point3;
use fyrox_core::math;
use fyrox_core::visitor::error::VisitError;
use fyrox_ui::{UiNode, UserInterface};
use serde::{Deserialize, Serialize};
use std::{
    error::Error,
    fmt::{Display, Formatter},
    path::{Path, PathBuf},
    sync::Arc,
};
use strum_macros::{AsRefStr, EnumString, VariantNames};

pub mod loader;

/// See module docs.
#[derive(Debug, Clone, Visit, Reflect)]
pub struct Model {
    #[visit(skip)]
    pub(crate) mapping: NodeMapping,
    #[visit(skip)]
    pub(crate) scene: Scene,
}

impl PrefabData for Model {
    type Graph = Graph;

    #[inline]
    fn graph(&self) -> &Self::Graph {
        &self.scene.graph
    }

    #[inline]
    fn mapping(&self) -> NodeMapping {
        self.mapping
    }
}

impl TypeUuidProvider for Model {
    fn type_uuid() -> Uuid {
        MODEL_RESOURCE_UUID
    }
}

/// Instantiation context holds additional data that could be useful for a prefab instantiation.
pub struct InstantiationContext<'a> {
    model: &'a ModelResource,
    dest_scene: &'a mut Scene,
    local_transform: Option<Transform>,
    ids: Option<&'a FxHashMap<Handle<Node>, SceneNodeId>>,
}

impl<'a> InstantiationContext<'a> {
    /// Sets the desired local rotation for the instance.
    pub fn with_rotation(mut self, rotation: UnitQuaternion<f32>) -> Self {
        self.local_transform
            .get_or_insert_with(Default::default)
            .set_rotation(rotation);
        self
    }

    /// Sets the desired local position for the instance.
    pub fn with_position(mut self, position: Vector3<f32>) -> Self {
        self.local_transform
            .get_or_insert_with(Default::default)
            .set_position(position);
        self
    }

    /// Sets the desired local scaling for the instance.
    pub fn with_scale(mut self, scale: Vector3<f32>) -> Self {
        self.local_transform
            .get_or_insert_with(Default::default)
            .set_scale(scale);
        self
    }

    /// Sets the desired local transform for the instance.
    pub fn with_transform(mut self, transform: Transform) -> Self {
        self.local_transform = Some(transform);
        self
    }

    /// Instantiates a prefab and assigns the given set of ids to the respective instances. The given
    /// hash map should contain pairs `(OriginalHandle, SceneNodeId)`. Original handle is a handle
    /// of a node from the prefab itself, not the instance handle! Use this method in pair with
    /// [`ModelResourceExtension::generate_ids`].
    ///
    /// This method should be used only if you need to instantiate an object on multiple clients in
    /// a multiplayer game with client-server model. This method ensures that the instances will
    /// have the same ids across all clients.
    pub fn with_ids(mut self, ids: &'a FxHashMap<Handle<Node>, SceneNodeId>) -> Self {
        self.ids = Some(ids);
        self
    }

    /// Finishes instantiation.
    pub fn finish(self) -> Handle<Node> {
        let model = self.model.clone();
        let data = model.data_ref();

        let resource_root = data.scene.graph.get_root();
        let (root, _) = ModelResource::instantiate_from(
            model.clone(),
            &data,
            resource_root,
            &mut self.dest_scene.graph,
            &mut |original_handle, node| {
                if original_handle == resource_root {
                    if let Some(transform) = self.local_transform.clone() {
                        *node.local_transform_mut() = transform;
                    }
                }

                if let Some(ids) = self.ids.as_ref() {
                    if let Some(id) = ids.get(&original_handle) {
                        node.instance_id = *id;
                    } else {
                        Log::warn(format!(
                            "No id specified for node {original_handle}! Random id will be used."
                        ))
                    }
                }
            },
        );

        // Explicitly mark as root node.
        self.dest_scene.graph[root].is_resource_instance_root = true;

        root
    }
}

/// Common trait that has animation retargetting methods.
pub trait AnimationSource {
    /// Prefab type.
    type Prefab: PrefabData<Graph = Self::SceneGraph>;
    /// Scene graph type.
    type SceneGraph: SceneGraph<Node = Self::Node, Prefab = Self::Prefab>;
    /// Scene node type.
    type Node: SceneGraphNode<SceneGraph = Self::SceneGraph, ResourceData = Self::Prefab>;

    /// Returns a reference to an inner graph.
    fn inner_graph(&self) -> &Self::SceneGraph;

    /// Tries to retarget animations from given model resource to a node hierarchy starting
    /// from `root` on a given scene.
    ///
    /// Animation retargeting allows you to "transfer" animation from a model to a model
    /// instance on a scene. Imagine you have a character that should have multiple animations
    /// like idle, run, shoot, walk, etc. and you want to store each animation in a separate
    /// file. Then when you creating a character on a level you want to have all possible
    /// animations assigned to a character, this is where this function comes into play:
    /// you just load a model of your character with skeleton, but without any animations,
    /// then you load several "models" which have only skeleton with some animation (such
    /// "models" can be considered as "animation" resources). After this you need to
    /// instantiate model on your level and retarget all animations you need to that instance
    /// from other "models". All you have after this is a handle to a model and bunch of
    /// handles to specific animations. After this animations can be blended in any combinations
    /// you need to. For example idle animation can be blended with walk animation when your
    /// character starts walking.
    ///
    /// # Notes
    ///
    /// Most of the 3d model formats can contain only one animation, so in most cases
    /// this function will return vector with only one animation.
    fn retarget_animations_directly(
        &self,
        root: Handle<Self::Node>,
        graph: &Self::SceneGraph,
        self_kind: ResourceKind,
    ) -> Vec<fyrox_animation::Animation<Handle<Self::Node>>> {
        let mut retargetted_animations = Vec::new();

        let model_graph = self.inner_graph();
        for src_node_ref in model_graph.linear_iter() {
            if let Some(src_animations) = src_node_ref
                .component_ref::<InheritableVariable<AnimationContainer<Handle<Self::Node>>>>()
            {
                for src_anim in src_animations.iter() {
                    let mut anim_copy = src_anim.clone();

                    // Remap animation track nodes from resource to instance. This is required
                    // because we've made a plain copy and it has tracks with node handles mapped
                    // to nodes of internal scene.
                    let src_anim_track_data = src_anim.tracks_data().state();
                    let Some(src_anim_track_data) = src_anim_track_data.data_ref() else {
                        continue;
                    };

                    for ref_track in src_anim_track_data.tracks.iter() {
                        let Some(ref_track_binding) =
                            src_anim.track_bindings().get(&ref_track.id())
                        else {
                            continue;
                        };

                        let ref_node = &model_graph.node(ref_track_binding.target);
                        let track_binding = anim_copy
                            .track_bindings_mut()
                            .get_mut(&ref_track.id())
                            .unwrap();
                        // Find instantiated node that corresponds to node in resource
                        match graph.find_by_name(root, ref_node.name()) {
                            Some((instance_node, _)) => {
                                track_binding.set_target(instance_node);
                            }
                            None => {
                                track_binding.set_target(Default::default());
                                Log::writeln(
                                    MessageKind::Error,
                                    format!(
                                        "Failed to retarget animation {:?} for node {}",
                                        self_kind,
                                        ref_node.name()
                                    ),
                                );
                            }
                        }
                    }

                    retargetted_animations.push(anim_copy);
                }
            }
        }

        retargetted_animations
    }

    /// Tries to retarget animations from given model resource to a node hierarchy starting
    /// from `root` on a given scene. Unlike [`Self::retarget_animations_directly`], it automatically
    /// adds retargetted animations to the specified animation player in the hierarchy of given `root`.
    ///
    /// # Panic
    ///
    /// Panics if `dest_animation_player` is invalid handle, or the node does not have [`AnimationContainer`]
    /// component.
    fn retarget_animations_to_player(
        &self,
        root: Handle<Self::Node>,
        dest_animation_player: Handle<Self::Node>,
        graph: &mut Self::SceneGraph,
        self_kind: ResourceKind,
    ) -> Vec<Handle<fyrox_animation::Animation<Handle<Self::Node>>>> {
        let mut animation_handles = Vec::new();

        let animations = self.retarget_animations_directly(root, graph, self_kind);

        let dest_animations = graph
            .node_mut(dest_animation_player)
            .component_mut::<InheritableVariable<AnimationContainer<Handle<Self::Node>>>>()
            .unwrap();

        for animation in animations {
            animation_handles.push(dest_animations.add(animation));
        }

        animation_handles
    }

    /// Tries to retarget animations from given model resource to a node hierarchy starting
    /// from `root` on a given scene. Unlike [`Self::retarget_animations_directly`], it automatically
    /// adds retargetted animations to a first animation player in the hierarchy of given `root`.
    ///
    /// # Panic
    ///
    /// Panics if there's no animation player in the given hierarchy (descendant nodes of `root`).
    fn retarget_animations(
        &self,
        root: Handle<Self::Node>,
        graph: &mut Self::SceneGraph,
        self_kind: ResourceKind,
    ) -> Vec<Handle<fyrox_animation::Animation<Handle<Self::Node>>>> {
        if let Some((animation_player, _)) = graph.find(root, &mut |n| {
            n.component_ref::<InheritableVariable<AnimationContainer<Handle<Self::Node>>>>()
                .is_some()
        }) {
            self.retarget_animations_to_player(root, animation_player, graph, self_kind)
        } else {
            Default::default()
        }
    }
}

/// Type alias for model resources.
pub type ModelResource = Resource<Model>;

/// Extension trait for model resources.
pub trait ModelResourceExtension: Sized {
    /// Tries to instantiate model from given resource. This is for internal use only and does not
    /// set `is_resource_instance_root`.
    fn instantiate_from<Pre>(
        model: ModelResource,
        model_data: &Model,
        handle: Handle<Node>,
        dest_graph: &mut Graph,
        pre_processing_callback: &mut Pre,
    ) -> (Handle<Node>, NodeHandleMap<Node>)
    where
        Pre: FnMut(Handle<Node>, &mut Node);

    /// Begins instantiation of the model.
    fn begin_instantiation<'a>(&'a self, dest_scene: &'a mut Scene) -> InstantiationContext<'a>;

    /// Tries to instantiate model from given resource.
    fn instantiate(&self, dest_scene: &mut Scene) -> Handle<Node>;

    /// Instantiates a prefab and places it at specified position and orientation in global coordinates.
    fn instantiate_at(
        &self,
        scene: &mut Scene,
        position: Vector3<f32>,
        orientation: UnitQuaternion<f32>,
    ) -> Handle<Node>;

    /// Instantiates a prefab and places it at specified position, orientation, scale in global
    /// coordinates and attaches it to the specified parent. This method automatically calculates
    /// required local position, rotation, scaling for the instance so it will remain at the same
    /// place in world space after attachment. This method could be useful if you need to instantiate
    /// an object at some other object.
    fn instantiate_and_attach(
        &self,
        scene: &mut Scene,
        parent: Handle<Node>,
        position: Vector3<f32>,
        face_towards: Vector3<f32>,
        scale: Vector3<f32>,
    ) -> Handle<Node>;

    /// Tries to retarget animations from given model resource to a node hierarchy starting
    /// from `root` on a given scene.
    ///
    /// Animation retargeting allows you to "transfer" animation from a model to a model
    /// instance on a scene. Imagine you have a character that should have multiple animations
    /// like idle, run, shoot, walk, etc. and you want to store each animation in a separate
    /// file. Then when you creating a character on a level you want to have all possible
    /// animations assigned to a character, this is where this function comes into play:
    /// you just load a model of your character with skeleton, but without any animations,
    /// then you load several "models" which have only skeleton with some animation (such
    /// "models" can be considered as "animation" resources). After this you need to
    /// instantiate model on your level and retarget all animations you need to that instance
    /// from other "models". All you have after this is a handle to a model and bunch of
    /// handles to specific animations. After this animations can be blended in any combinations
    /// you need to. For example idle animation can be blended with walk animation when your
    /// character starts walking.
    ///
    /// # Notes
    ///
    /// Most of the 3d model formats can contain only one animation, so in most cases
    /// this function will return vector with only one animation.
    fn retarget_animations_directly(&self, root: Handle<Node>, graph: &Graph) -> Vec<Animation>;

    /// Tries to retarget animations from given model resource to a node hierarchy starting
    /// from `root` on a given scene. Unlike [`Self::retarget_animations_directly`], it automatically
    /// adds retargetted animations to the specified animation player in the hierarchy of given `root`.
    ///
    /// # Panic
    ///
    /// Panics if `dest_animation_player` is invalid handle, or the node does not have [`AnimationContainer`]
    /// component.
    fn retarget_animations_to_player(
        &self,
        root: Handle<Node>,
        dest_animation_player: Handle<Node>,
        graph: &mut Graph,
    ) -> Vec<Handle<Animation>>;

    /// Tries to retarget animations from given model resource to a node hierarchy starting
    /// from `root` on a given scene. Unlike [`Self::retarget_animations_directly`], it automatically
    /// adds retargetted animations to a first animation player in the hierarchy of given `root`.
    ///
    /// # Panic
    ///
    /// Panics if there's no animation player in the given hierarchy (descendant nodes of `root`).
    fn retarget_animations(&self, root: Handle<Node>, graph: &mut Graph) -> Vec<Handle<Animation>>;

    /// Generates a set of unique IDs for every node in the model. Use this method in pair with
    /// [`ModelResource::begin_instantiation`].
    fn generate_ids(&self) -> FxHashMap<Handle<Node>, SceneNodeId>;
}

impl AnimationSource for Model {
    type Prefab = Model;
    type SceneGraph = Graph;
    type Node = Node;

    fn inner_graph(&self) -> &Self::SceneGraph {
        &self.scene.graph
    }
}

impl AnimationSource for UserInterface {
    type Prefab = UserInterface;
    type SceneGraph = UserInterface;
    type Node = UiNode;

    fn inner_graph(&self) -> &Self::SceneGraph {
        self
    }
}

impl ModelResourceExtension for ModelResource {
    /// Copy the given model into the given graph.
    /// * `model`: The resource handle of the model, which put into the created nodes as their
    ///   [`Base::resource`](crate::scene::base::Base::resource) to indicate which model
    ///   the node was instantiated from.
    /// * `model_data`: A borrow of the data contained in `model`.
    /// * `handle`: The handle of the node within `model` that should be instantiated, typically
    ///   the root of the model.
    /// * `dest_graph`: A mutable borrow of the node graph that will contain the newly created copy.
    /// * `pre_processing_callback`: A function that takes a node handle and a mutable node.
    ///   The handle belongs to the original node in the model. The node is a copy of the original
    ///   node, except that parent handle and child handles have been removed. This is a node
    ///   that will be inserted into `dest_graph`.
    fn instantiate_from<Pre>(
        model: ModelResource,
        model_data: &Model,
        handle: Handle<Node>,
        dest_graph: &mut Graph,
        pre_processing_callback: &mut Pre,
    ) -> (Handle<Node>, NodeHandleMap<Node>)
    where
        Pre: FnMut(Handle<Node>, &mut Node),
    {
        let (root, old_to_new) = model_data.scene.graph.copy_node(
            handle,
            dest_graph,
            &mut |_, _| true,
            pre_processing_callback,
            &mut |_, original_handle, node| {
                node.set_inheritance_data(original_handle, model.clone());
            },
        );

        dest_graph.update_hierarchical_data_for_descendants(root);

        (root, old_to_new)
    }

    fn begin_instantiation<'a>(&'a self, dest_scene: &'a mut Scene) -> InstantiationContext<'a> {
        if !self.is_ok() {
            Log::err(format!(
                "Instantiating a model from a resource that is not loaded: {self:?}"
            ));
        }
        InstantiationContext {
            model: self,
            dest_scene,
            local_transform: None,
            ids: None,
        }
    }

    fn instantiate(&self, dest_scene: &mut Scene) -> Handle<Node> {
        self.begin_instantiation(dest_scene).finish()
    }

    fn instantiate_at(
        &self,
        scene: &mut Scene,
        position: Vector3<f32>,
        orientation: UnitQuaternion<f32>,
    ) -> Handle<Node> {
        self.begin_instantiation(scene)
            .with_rotation(orientation)
            .with_position(position)
            .finish()
    }

    fn instantiate_and_attach(
        &self,
        scene: &mut Scene,
        parent: Handle<Node>,
        position: Vector3<f32>,
        face_towards: Vector3<f32>,
        scale: Vector3<f32>,
    ) -> Handle<Node> {
        let parent_scale = scene.graph.global_scale(parent);

        let parent_inv_transform = scene.graph[parent]
            .global_transform()
            .try_inverse()
            .unwrap_or_default();

        let local_position = parent_inv_transform
            .transform_point(&Point3::from(position))
            .coords;

        let local_rotation =
            math::vector_to_quat(parent_inv_transform.transform_vector(&face_towards));

        // Discard parent's scale.
        let local_scale = scale.component_div(&parent_scale);

        let instance = self
            .begin_instantiation(scene)
            .with_position(local_position)
            .with_rotation(local_rotation)
            .with_scale(local_scale)
            .finish();

        scene.graph.link_nodes(instance, parent);

        instance
    }

    fn retarget_animations_directly(&self, root: Handle<Node>, graph: &Graph) -> Vec<Animation> {
        let mut header = self.state();
        let self_kind = header.kind();
        if let Some(model) = header.data() {
            model.retarget_animations_directly(root, graph, self_kind)
        } else {
            Default::default()
        }
    }

    fn retarget_animations_to_player(
        &self,
        root: Handle<Node>,
        dest_animation_player: Handle<Node>,
        graph: &mut Graph,
    ) -> Vec<Handle<Animation>> {
        let mut header = self.state();
        let self_kind = header.kind();
        if let Some(model) = header.data() {
            model.retarget_animations_to_player(root, dest_animation_player, graph, self_kind)
        } else {
            Default::default()
        }
    }

    fn retarget_animations(&self, root: Handle<Node>, graph: &mut Graph) -> Vec<Handle<Animation>> {
        let mut header = self.state();
        let self_kind = header.kind();
        if let Some(model) = header.data() {
            model.retarget_animations(root, graph, self_kind)
        } else {
            Default::default()
        }
    }

    fn generate_ids(&self) -> FxHashMap<Handle<Node>, SceneNodeId> {
        let data = self.data_ref();
        data.scene
            .graph
            .pair_iter()
            .map(|(h, _)| (h, SceneNodeId(Uuid::new_v4())))
            .collect()
    }
}

impl ResourceData for Model {
    fn type_uuid(&self) -> Uuid {
        <Self as TypeUuidProvider>::type_uuid()
    }

    fn save(&mut self, path: &Path) -> Result<(), Box<dyn Error>> {
        let mut visitor = Visitor::new();
        self.scene.save("Scene", &mut visitor)?;
        visitor.save_ascii_to_file(path)?;
        Ok(())
    }

    fn can_be_saved(&self) -> bool {
        true
    }

    fn try_clone_box(&self) -> Option<Box<dyn ResourceData>> {
        Some(Box::new(self.clone()))
    }
}

impl Default for Model {
    fn default() -> Self {
        Self {
            mapping: NodeMapping::UseNames,
            scene: Scene::new(),
        }
    }
}

/// Defines a way of searching materials when loading a model resource from foreign file format such as FBX.
///
/// # Motivation
///
/// Most 3d model file formats store paths to external resources (textures and other things) as absolute paths,
/// which makes it impossible to use with "location-independent" application like games. To fix that issue, the
/// engine provides few ways of resolving paths to external resources. The engine starts resolving by stripping
/// everything but file name from an external resource's path, then it uses one of the following methods to find
/// a texture with the file name. It could look up on folders hierarchy by using [`MaterialSearchOptions::RecursiveUp`]
/// method, or even use global search starting from the working directory of your game
/// ([`MaterialSearchOptions::WorkingDirectory`])
#[derive(
    Clone,
    Debug,
    Visit,
    PartialEq,
    Eq,
    Deserialize,
    Serialize,
    Reflect,
    AsRefStr,
    EnumString,
    VariantNames,
)]
pub enum MaterialSearchOptions {
    /// Search in specified materials directory. It is suitable for cases when
    /// your model resource use shared textures.
    ///
    /// # Platform specific
    ///
    /// Works on every platform.
    MaterialsDirectory(PathBuf),

    /// Recursive-up search. It is suitable for cases when textures are placed
    /// near your model resource. This is **default** option.
    ///
    /// # Platform specific
    ///
    /// Works on every platform.
    RecursiveUp,

    /// Global search starting from working directory. Slowest option with a lot of ambiguities -
    /// it may load unexpected file in cases when there are two or more files with same name but
    /// lying in different directories.
    ///
    /// # Platform specific
    ///
    /// WebAssembly - **not supported** due to lack of file system.
    WorkingDirectory,

    /// Try to use paths stored in the model resource directly. This options has limited usage,
    /// it is suitable to load animations, or any other model which does not have any materials.
    ///
    /// # Important notes
    ///
    /// RGS (native engine scenes) files should be loaded with this option by default, otherwise
    /// the engine won't be able to correctly find materials.
    UsePathDirectly,
}

uuid_provider!(MaterialSearchOptions = "11634aa0-cf8f-4532-a8cd-c0fa6ef804f1");

impl Default for MaterialSearchOptions {
    fn default() -> Self {
        Self::RecursiveUp
    }
}

impl MaterialSearchOptions {
    /// A helper to create MaterialsDirectory variant.
    pub fn materials_directory<P: AsRef<Path>>(path: P) -> Self {
        Self::MaterialsDirectory(path.as_ref().to_path_buf())
    }
}

/// A set of options that will be applied to a model resource when loading it from external source.
///
/// # Details
///
/// The engine has a convenient way of storing import options in a `.options` files. For example you may
/// have a `foo.fbx` 3d model, to change import options create a new file with additional `.options`
/// extension: `foo.fbx.options`. The content of an options file could be something like this:
///
/// ```text
/// (
///     material_search_options: RecursiveUp
/// )
/// ```
///
/// Check documentation of the field of the structure for more info about each parameter.
#[derive(Clone, Debug, PartialEq, Serialize, Deserialize, Default, Reflect, Eq)]
pub struct ModelImportOptions {
    /// See [`MaterialSearchOptions`] docs for more info.
    #[serde(default)]
    pub material_search_options: MaterialSearchOptions,
}

impl ImportOptions for ModelImportOptions {}

/// All possible errors that may occur while trying to load model from some
/// data source.
#[derive(Debug)]
pub enum ModelLoadError {
    /// An error occurred while reading a data source.
    Visit(VisitError),
    /// Format is not supported.
    NotSupported(String),
    /// An error occurred while loading FBX file.
    Fbx(FbxError),
}

impl Display for ModelLoadError {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        match self {
            ModelLoadError::Visit(v) => {
                write!(f, "An error occurred while reading a data source: {v}")
            }
            ModelLoadError::NotSupported(v) => {
                write!(f, "Model format is not supported: {v}")
            }
            ModelLoadError::Fbx(v) => v.fmt(f),
        }
    }
}

impl From<FbxError> for ModelLoadError {
    fn from(fbx: FbxError) -> Self {
        ModelLoadError::Fbx(fbx)
    }
}

impl From<VisitError> for ModelLoadError {
    fn from(e: VisitError) -> Self {
        ModelLoadError::Visit(e)
    }
}

impl Model {
    /// Creates a new Model instance using the given node mapping and the given scene. It could be
    /// used to create your own Model resources.
    pub fn new(mapping: NodeMapping, scene: Scene) -> Self {
        Self { mapping, scene }
    }

    pub(crate) async fn load<P: AsRef<Path>>(
        path: P,
        io: &dyn ResourceIo,
        serialization_context: Arc<SerializationContext>,
        resource_manager: ResourceManager,
        model_import_options: ModelImportOptions,
    ) -> Result<Self, ModelLoadError> {
        let extension = path
            .as_ref()
            .extension()
            .unwrap_or_default()
            .to_string_lossy()
            .as_ref()
            .to_lowercase();
        let (scene, mapping) = match extension.as_ref() {
            "fbx" => {
                let mut scene = Scene::new();
                if let Some(filename) = path.as_ref().file_name() {
                    let root = scene.graph.get_root();
                    scene.graph[root].set_name(filename.to_string_lossy());
                }
                fbx::load_to_scene(
                    &mut scene,
                    resource_manager,
                    io,
                    path.as_ref(),
                    &model_import_options,
                )
                .await?;
                // Set NodeMapping::UseNames as mapping here because FBX does not have
                // any persistent unique ids, and we have to use names.
                (scene, NodeMapping::UseNames)
            }
            // Scene can be used directly as model resource. Such scenes can be created in
            // Fyroxed.
            "rgs" => (
                SceneLoader::from_file(
                    path.as_ref(),
                    io,
                    serialization_context,
                    resource_manager.clone(),
                )
                .await?
                .0
                .finish()
                .await,
                NodeMapping::UseHandles,
            ),
            // TODO: Add more formats.
            _ => {
                return Err(ModelLoadError::NotSupported(format!(
                    "Unsupported model resource format: {extension}"
                )))
            }
        };

        Ok(Self { scene, mapping })
    }

    /// Returns shared reference to internal scene, there is no way to obtain
    /// mutable reference to inner scene because resource is immutable source
    /// of data.
    pub fn get_scene(&self) -> &Scene {
        &self.scene
    }

    /// Searches for a node in the model, starting from specified node using the specified closure. Returns a tuple with a
    /// handle and a reference to the found node. If nothing is found, it returns [`None`].
    pub fn find_node_by_name(&self, name: &str) -> Option<(Handle<Node>, &Node)> {
        self.scene.graph.find_by_name_from_root(name)
    }

    pub(crate) fn get_scene_mut(&mut self) -> &mut Scene {
        &mut self.scene
    }
}