.vscode/launch.json

@@ -83,6 +83,28 @@
             },
             "args": [],
             "cwd": "${workspaceFolder}/lyra-ecs"
+        },
+        {
+            "type": "lldb",
+            "request": "launch",
+            "name": "Debug unit tests in executable 'lyra-scene'",
+            "cargo": {
+                "args": [
+                    "test",
+                    "--no-run",
+                    "--lib",
+                    "--package=lyra-scene",
+                    //"command::tests::deferred_commands",
+                    //"--",
+                    //"--exact --nocapture"
+                ],
+                "filter": {
+                    "name": "lyra-scene",
+                    "kind": "lib"
+                }
+            },
+            "args": [],
+            "cwd": "${workspaceFolder}/lyra-scene"
         }
     ]
 }

Cargo.lock

@@ -1855,6 +1855,14 @@ dependencies = [
  "uuid",
 ]
 
+[[package]]
+name = "lyra-scene"
+version = "0.1.0"
+dependencies = [
+ "lyra-ecs",
+ "lyra-math",
+]
+
 [[package]]
 name = "lyra-scripting"
 version = "0.1.0"

Cargo.toml

@@ -10,7 +10,7 @@ members = [
     "lyra-ecs",
     "lyra-reflect",
     "lyra-scripting",
-    "lyra-game", "lyra-math"]
+    "lyra-game", "lyra-math", "lyra-scene"]
 
 [features]
 scripting = ["dep:lyra-scripting"]

lyra-scene/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "lyra-scene"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+lyra-ecs = { path = "../lyra-ecs", features = [ "math" ] }
+lyra-math = { path = "../lyra-math" }

lyra-scene/src/lib.rs

@@ -0,0 +1,305 @@
+use std::{collections::VecDeque, ops::{Deref, DerefMut}};
+
+use lyra_ecs::{query::Entities, relation::ChildOf, Bundle, Component, Entity, World};
+
+// So we can use lyra_ecs::Component derive macro
+pub(crate) mod lyra_engine {
+    pub(crate) mod ecs {
+        pub use lyra_ecs::*;
+    }
+}
+
+mod node;
+use lyra_math::{Transform, Vec3};
+pub use node::*;
+
+/// A flag spawned on all scene node entities
+#[derive(Component)]
+pub struct SceneNodeFlag;
+
+/// A flag spawned on only the scene root node
+#[derive(Component)]
+pub struct SceneNodeRoot;
+
+enum MutCow<'a, T> {
+    Mut(&'a mut T),
+    Owned(T),
+}
+
+impl<'a, T> Deref for MutCow<'a, T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        match self {
+            MutCow::Mut(t) => t,
+            MutCow::Owned(t) => t,
+        }
+    }
+}
+
+impl<'a, T> DerefMut for MutCow<'a, T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        match self {
+            MutCow::Mut(t) => t,
+            MutCow::Owned(t) => t,
+        }
+    }
+}
+
+/// A SceneGraph is a Graph of nodes that represents the hierarchy of a scene.
+/// 
+/// This SceneGraph is special in the sense that it is literally just an ECS world with methods
+/// implemented for it that make it easier to use for a SceneGraph.
+//#[derive(Default)]
+pub struct SceneGraph<'a> {
+    pub(crate) world: MutCow<'a, World>,
+    root_node: SceneNode,
+}
+
+impl<'a> SceneGraph<'a> {
+    /// Create a new SceneGraph with its own ECS World.
+    pub fn new() -> Self {
+        let mut world = World::new();
+        
+        let e = world.spawn((Transform::from_translation(Vec3::new(0.0, 0.0, 0.0)), SceneNodeRoot));
+        let root = SceneNode::new(None, e);
+
+        Self {
+            world: MutCow::Owned(world),
+            root_node: root
+        }
+    }
+
+    /// Retrieve a SceneGraph from an ECS World.
+    /// 
+    /// Returns `None` if the `root_entity` was not created from a `SceneGraph` that was later
+    /// inserted into another world with [`SceneGraph::into_world`].
+    pub fn from_world(world: &'a mut World, root_entity: Entity) -> Option<Self> {
+        if world.view_one::<(&SceneNodeRoot, &Transform)>(root_entity).get().is_none() {
+            None
+        } else {
+            Some(Self {
+                world: MutCow::Mut(world),
+                root_node: SceneNode::new(None, root_entity),
+            })
+        }
+    }
+
+    /// Create a new SceneGraph inside an existing ECS World.
+    pub fn new_from_world(world: &'a mut World) -> Self {
+        let root_en = world.spawn((Transform::from_translation(Vec3::new(0.0, 0.0, 0.0)), SceneNodeRoot));
+        let root = SceneNode::new(None, root_en);
+
+        Self {
+            world: MutCow::Mut(world),
+            root_node: root,
+        }
+    }
+
+    /// Consume the SceneGraph, inserting its internal world into the provided world.
+    /// 
+    /// The `into` World will contain all nodes of the SceneGraph. You could iterate through the
+    /// SceneGraph manually if you'd like. The root entity has a [`SceneNodeRoot`] flag component,
+    /// and a Transform component. The children nodes have a [`SceneNodeFlag`] component and a 
+    /// Transform component. The transforms of the children will be local, you must find its world
+    /// transform by traversing up the hierarchy of the scene manually with the `ChildOf` relation.
+    /// 
+    /// Returns: the Entity of the root node in the provided world.
+    pub fn into_world(mut self, into: &mut World) -> Entity {
+        // first insert the root entity into the World.
+        let v = self.world.view_one::<&Transform>(self.root_node.entity());
+        let pos = *v.get().unwrap();
+        let new_root = into.spawn((pos, SceneNodeRoot));
+
+        // now process the children of the root node.
+        Self::traverse_inserting_into(&mut self.world, self.root_node.entity(), new_root, into);
+        new_root
+    }
+
+    /// Recursively traverse the `from` world, starting at `node_en`, inserting the
+    /// children entity into the world.
+    /// 
+    /// Parameters:
+    /// * `scene_world` - The world that the SceneGraph exists in
+    /// * `scene_en` - The entity of the parent entity inside of the `scene_world`.
+    /// * `parent_en` - The entity of the parent entity inside of the `into` world.
+    /// * `into` - The world to insert the SceneGraph world into.
+    fn traverse_inserting_into(scene_world: &mut World, scene_en: Entity, parent_en: Entity, into: &mut World) {
+        let v = scene_world.view::<(Entities, &Transform)>()
+            .relates_to::<ChildOf>(scene_en);
+
+        // unfortunately, the borrow checker exists, and wasn't happy that `scene_world` was
+        // immutably borrowed with the view (v), and being mutably borrowed in the
+        // recursive call.
+        let mut child_entities = VecDeque::new();
+
+        for ((child_scene_en, pos), _rel) in v.iter() {
+            let into_en = into.spawn((*pos, SceneNodeFlag));
+            into.add_relation(into_en, ChildOf, parent_en);
+
+            child_entities.push_back((child_scene_en, into_en));
+        }
+
+        while let Some((child_scene_en, into_en)) = child_entities.pop_front() {
+            Self::traverse_inserting_into(scene_world, child_scene_en, into_en, into);
+        }
+    }
+
+    /// Adds a node to the root node of the SceneGraph.
+    /// 
+    /// The spawned entity will have a `ChildOf` relation targeting the root node, the
+    /// `SceneNodeFlag` component is also added to the entity.
+    pub fn add_node<B: Bundle>(&mut self, local_transform: Transform, bundle: B) -> SceneNode {
+        let node = self.root_node.clone();
+        self.add_node_under(&node, local_transform, bundle)
+    }
+
+    /// Add a node under a parent node.
+    /// 
+    /// The spawned entity will have a `ChildOf` relation targeting the provided parent node,
+    /// the `SceneNodeFlag` component is also added to the entity.
+    pub fn add_node_under<B: Bundle>(&mut self, parent: &SceneNode, local_transform: Transform, bundle: B) -> SceneNode {
+        world_add_child_node(&mut self.world, parent, local_transform, bundle)
+    }
+
+    /// Traverses down the SceneGraph, calling `callback` with each SceneNode and its world transform.
+    /// 
+    /// The traversal does not include the root scene node.
+    pub fn traverse_down<F>(&self, mut callback: F)
+    where
+        F: FnMut(&SceneNode, Transform),
+    {
+        self.traverse_down_from(self.root_node.clone(), &mut callback);
+    }
+
+    /// Traverses down the SceneGraph from a starting node, calling `callback` with each
+    /// SceneNode and its world transform.
+    fn traverse_down_from<F>(&self, start: SceneNode, callback: &mut F)
+    where
+        F: FnMut(&SceneNode, Transform),
+    {
+        let v = self.world.view::<(Entities, &Transform)>()
+            .relates_to::<ChildOf>(start.entity());
+
+        for ((e, _), _rel) in v.iter() {
+            let node = SceneNode::new(Some(start.entity()), e);
+            let world_pos = node.world_transform(self);
+            callback(&node, world_pos);
+
+            self.traverse_down_from(node, callback);
+        }
+    }
+}
+
+/// Add a node under a parent node.
+/// 
+/// The spawned entity will have a `ChildOf` relation targeting the provided parent node,
+/// the `SceneNodeFlag` component is also added to the entity.
+pub(crate) fn world_add_child_node<B: Bundle>(world: &mut World, parent: &SceneNode, local_transform: Transform, bundle: B) -> SceneNode {
+    let e = world.spawn(bundle);
+    world.insert(e, (SceneNodeFlag, local_transform));
+    world.add_relation(e, ChildOf, parent.entity());
+
+    SceneNode::new(Some(parent.entity()), e)
+}
+
+#[cfg(test)]
+pub mod tests {
+    use lyra_ecs::{query::Entities, relation::ChildOf, Component, World};
+    use lyra_math::{Transform, Vec3};
+
+    use crate::{lyra_engine, SceneGraph, SceneNodeRoot};
+
+    #[derive(Component)]
+    pub struct FakeMesh;
+
+    #[test]
+    fn single_node_hierarchy() {
+        let mut scene = SceneGraph::new();
+
+        let a = scene.add_node(Transform::from_translation(Vec3::new(10.0, 10.0, 10.0)), FakeMesh);
+        assert!(a.parent(&scene).unwrap() == scene.root_node);
+    }
+
+    #[test]
+    fn double_node_hierarchy() {
+        let mut scene = SceneGraph::new();
+
+        let a = scene.add_node(Transform::from_translation(Vec3::new(10.0, 10.0, 10.0)), FakeMesh);
+        assert!(a.parent(&scene).unwrap() == scene.root_node);
+
+        let b = a.add_node(&mut scene, Transform::from_translation(Vec3::new(50.0, 50.0, 50.0)), FakeMesh);
+        assert!(b.parent(&scene).unwrap() == a);
+    }
+
+    #[test]
+    fn traverse_down() {
+        let v2s = vec![Vec3::new(10.0, 10.0, 10.0), Vec3::new(50.0, 50.0, 50.0)];
+
+        let mut scene = SceneGraph::new();
+
+        let a = scene.add_node(Transform::from_translation(v2s[0]), FakeMesh);
+        assert!(a.parent(&scene).unwrap() == scene.root_node);
+        let b = a.add_node(&mut scene, Transform::from_translation(v2s[1]), FakeMesh);
+        assert!(b.parent(&scene).unwrap() == a);
+
+        let mut idx = 0;
+        scene.traverse_down(|_e, pos| {
+            if idx == 0 {
+                assert_eq!(pos, Transform::from_translation(v2s[idx]));
+            } else if idx == 1 {
+                let t = v2s.iter().sum();
+                assert_eq!(pos, Transform::from_translation(t));
+            }
+
+            idx += 1;
+        });
+    }
+
+    #[test]
+    fn inserting_and_from_world() {
+        let v2s = vec![Vec3::new(10.0, 10.0, 10.0), Vec3::new(50.0, 50.0, 50.0)];
+
+        let mut scene = SceneGraph::new();
+
+        let a = scene.add_node(Transform::from_translation(v2s[0]), FakeMesh);
+        assert!(a.parent(&scene).unwrap() == scene.root_node);
+        let b = a.add_node(&mut scene, Transform::from_translation(v2s[1]), FakeMesh);
+        assert!(b.parent(&scene).unwrap() == a);
+
+        let mut other_world = World::new();
+        let root = scene.into_world(&mut other_world);
+        
+        // check all of the entities inside of the World
+        let (root_pos, _) = other_world.view_one::<(&Transform, &SceneNodeRoot)>(root).get().unwrap();
+        assert_eq!(*root_pos, Transform::from_xyz(0.0, 0.0, 0.0));
+
+        let ((child_en, child_pos), _)  = other_world.view::<(Entities, &Transform)>()
+            .relates_to::<ChildOf>(root).iter().next().unwrap();
+        assert_eq!(*child_pos, Transform::from_translation(v2s[0]));
+
+        let ((_, childchild_pos), _)  = other_world.view::<(Entities, &Transform)>()
+            .relates_to::<ChildOf>(child_en).iter().next().unwrap();
+        assert_eq!(*childchild_pos, Transform::from_translation(v2s[1]));
+        
+        drop(root_pos);
+        drop(child_pos);
+        drop(childchild_pos);
+
+        // Now get the SceneGraph inside the World and use the nice utility tools to traverse it.
+        let scene = SceneGraph::from_world(&mut other_world, root)
+            .expect("Failed to get SceneGraph from World!");
+
+        let mut idx = 0;
+        scene.traverse_down(|_e, pos| {
+            if idx == 0 {
+                assert_eq!(pos, Transform::from_translation(v2s[idx]));
+            } else if idx == 1 {
+                let t = v2s.iter().sum();
+                assert_eq!(pos, Transform::from_translation(t));
+            }
+
+            idx += 1;
+        });
+    }
+}

lyra-scene/src/node.rs

@@ -0,0 +1,101 @@
+use lyra_ecs::{query::Entities, relation::{ChildOf, RelationOriginComponent}, Bundle, Entity};
+use lyra_math::Transform;
+
+use crate::SceneGraph;
+
+#[derive(Clone, PartialEq, Eq)]
+pub struct SceneNode {
+    //world: WorldLock,
+    parent: Option<Entity>,
+    entity: Entity
+}
+
+impl SceneNode {
+    pub fn new(parent: Option<Entity>, entity: Entity) -> Self {
+        Self {
+            parent,
+            entity,
+        }
+    }
+
+    /// If this node has a parent, retrieves the parent node from the SceneGraph.
+    pub fn parent(&self, graph: &SceneGraph) -> Option<SceneNode> {
+        if let Some(parent) = self.parent {
+            let v = graph.world.view_one::<&RelationOriginComponent<ChildOf>>(parent);
+            
+            let p_parent = if let Some(pp) = v.get() {
+                Some(pp.target())
+            } else { None };
+
+            Some(SceneNode::new(p_parent, parent))
+        } else {
+            None
+        }
+    }
+
+    pub fn parent_entity(&self) -> Option<Entity> {
+        self.parent
+    }
+
+    pub fn children(&self, graph: &SceneGraph) -> Vec<SceneNode> {
+        let v = graph.world.view::<Entities>()
+            .relates_to::<ChildOf>(self.entity);
+
+        v.into_iter().map(|(e, _)| SceneNode::new(Some(self.entity), e)).collect()
+    }
+
+    pub fn entity(&self) -> Entity {
+        self.entity
+    }
+
+    /// Add a child node to this node.
+    /// 
+    /// The spawned entity backing the scene node will have a `ChildOf` relation targeting
+    /// the provided parent node, the `SceneNodeFlag` component is also added to the entity.
+    pub fn add_node<B: Bundle>(&self, graph: &mut SceneGraph, local_transform: Transform, bundle: B) -> SceneNode {
+        graph.add_node_under(self, local_transform, bundle)
+    }
+
+    pub fn local_transform(&self, graph: &SceneGraph) -> Transform {
+        let v = graph.world.view_one::<&Transform>(self.entity);
+
+        let t = v.get().expect("Somehow the SceneNode is missing its Transform!");
+        t.clone()
+    }
+
+    /// Retrieves the world transform of the Node.
+    /// 
+    /// This traverses up the SceneGraph from this node.
+    pub fn world_transform(&self, graph: &SceneGraph) -> Transform {
+        match self.parent(graph) {
+            Some(parent) => {
+                let pt = parent.world_transform(graph);
+                pt + self.local_transform(graph)
+            },
+            None => {
+                self.local_transform(graph)
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use lyra_math::{Transform, Vec3};
+    
+    use crate::{tests::FakeMesh, SceneGraph};
+
+    #[test]
+    fn node_world_transform() {
+        let mut scene = SceneGraph::new();
+
+        let a = scene.add_node(Transform::from_translation(Vec3::new(10.0, 10.0, 10.0)), FakeMesh);
+        assert!(a.parent(&scene).unwrap() == scene.root_node);
+        
+        let b = a.add_node(&mut scene, Transform::from_translation(Vec3::new(50.0, 50.0, 50.0)), FakeMesh);
+        assert!(b.parent(&scene).unwrap() == a);
+
+        let wrld_tran = b.world_transform(&scene);
+        assert_eq!(wrld_tran, Transform::from_translation(Vec3::new(60.0, 60.0, 60.0)));
+    }
+}