From 55c50f7185b403ae0d8f8727e309845b8046816f Mon Sep 17 00:00:00 2001
From: Carter Anderson <mcanders1@gmail.com>
Date: Sat, 11 Jan 2020 01:46:51 -0800
Subject: [PATCH] refactor app startup. AppBuilder. clean up examples

---
 examples/empty.rs                             |   7 +
 examples/instancing.rs                        | 212 ++++++++++
 examples/load_model.rs                        |   9 +-
 examples/parenting.rs                         | 110 ++++++
 examples/simple.rs                            | 368 ++----------------
 examples/ui.rs                                | 108 +++++
 src/app/app_builder.rs                        |  55 +++
 src/app/app_stage.rs                          |  18 +
 src/{application.rs => app/mod.rs}            |  72 ++--
 src/core/mod.rs                               |  21 +-
 src/lib.rs                                    |   4 +-
 src/render/passes/forward_instanced/mod.rs    |   4 +
 src/render/passes/ui/mod.rs                   |   4 +
 src/render/render_graph/mod.rs                |  55 +--
 .../light_resource_manager.rs                 |   4 +
 .../material_resource_manager.rs              |   4 +
 16 files changed, 633 insertions(+), 422 deletions(-)
 create mode 100644 examples/empty.rs
 create mode 100644 examples/instancing.rs
 create mode 100644 examples/parenting.rs
 create mode 100644 examples/ui.rs
 create mode 100644 src/app/app_builder.rs
 create mode 100644 src/app/app_stage.rs
 rename src/{application.rs => app/mod.rs} (64%)

diff --git a/examples/empty.rs b/examples/empty.rs
new file mode 100644
index 0000000000..2884e24afc
--- /dev/null
+++ b/examples/empty.rs
@@ -0,0 +1,7 @@
+use bevy::*;
+
+fn main() {
+    AppBuilder::new()
+        .add_defaults()
+        .run();
+}
\ No newline at end of file
diff --git a/examples/instancing.rs b/examples/instancing.rs
new file mode 100644
index 0000000000..b55ddc247a
--- /dev/null
+++ b/examples/instancing.rs
@@ -0,0 +1,212 @@
+use bevy::*;
+use bevy::{render::*, asset::{Asset, AssetStorage, Handle}, math::{Mat4, Vec3}, Schedulable};
+use rand::{rngs::StdRng, Rng, SeedableRng, random};
+use std::collections::VecDeque;
+
+struct Person;
+
+struct Velocity {
+    pub value: math::Vec3,
+}
+
+struct NavigationPoint {
+    pub target: math::Vec3,
+}
+
+struct Wander {
+    pub duration_bounds: math::Vec2,
+    pub distance_bounds: math::Vec2,
+    pub duration: f32,
+    pub elapsed: f32,
+}
+
+fn main() {
+    AppBuilder::new()
+        .add_defaults()
+        .setup(&setup)
+        .run();
+}
+
+fn setup(world: &mut World, scheduler: &mut SystemScheduler<AppStage>) {
+    let cube = Mesh::load(MeshType::Cube);
+    let cube_handle = {
+        let mut mesh_storage = world.resources.get_mut::<AssetStorage<Mesh, MeshType>>().unwrap();
+        mesh_storage.add(cube, "cube")
+    };
+
+    let transform_system_bundle = transform_system_bundle::build(world);
+    scheduler.add_systems(AppStage::Update, transform_system_bundle);
+    scheduler.add_system(AppStage::Update, build_wander_system());
+    scheduler.add_system(AppStage::Update, build_navigate_system());
+    scheduler.add_system(AppStage::Update, build_move_system());
+    scheduler.add_system(AppStage::Update, build_print_status_system());
+
+    world.insert((), vec![
+        // lights
+        (
+            Light {
+                color: wgpu::Color {
+                    r: 0.8,
+                    g: 0.8,
+                    b: 0.5,
+                    a: 1.0,
+                },
+                fov: f32::to_radians(60.0),
+                depth: 0.1 .. 50.0,
+                target_view: None,
+            },
+            Material::new(math::vec4(0.5, 0.3, 0.3, 1.0)),
+            LocalToWorld::identity(),
+            Translation::new(4.0, -4.0, 5.0),
+            Rotation::from_euler_angles(0.0, 0.0, 0.0)
+        ),
+    ]);
+
+    world.insert((), vec![
+        // camera
+        (
+            Camera::new(CameraType::Projection {
+                fov: std::f32::consts::PI / 4.0,
+                near: 1.0,
+                far: 1000.0,
+                aspect_ratio: 1.0,
+            }),
+            ActiveCamera,
+            LocalToWorld(Mat4::look_at_rh(
+                Vec3::new(6.0, -40.0, 20.0),
+                Vec3::new(0.0, 0.0, 0.0),
+                Vec3::new(0.0, 0.0, 1.0),)),
+        )
+    ]);
+
+    let mut rng = StdRng::from_entropy();
+    for _ in 0 .. 70000 {
+        create_person(world, cube_handle.clone(),
+            Translation::new(rng.gen_range(-50.0, 50.0), 0.0, rng.gen_range(-50.0, 50.0)));
+    }
+}
+
+fn build_wander_system() -> Box<dyn Schedulable> {
+    let mut rng = StdRng::from_entropy();
+    
+    SystemBuilder::new("Wander")
+        .read_resource::<Time>()
+        .with_query(<(
+            Read<Person>,
+            Read<Translation>,
+            Write<Wander>,
+            Write<NavigationPoint>,
+        )>::query())
+        .build(move |
+            _, world,
+            time ,
+            person_query| {
+            for (_, translation, mut wander, mut navigation_point) in person_query.iter(world) {
+                wander.elapsed += time.delta_seconds;
+                if wander.elapsed >= wander.duration {
+                    let direction = math::vec3(
+                        rng.gen_range(-1.0, 1.0),
+                        rng.gen_range(-1.0, 1.0),
+                        rng.gen_range(0.0, 0.001),
+                    ).normalize();
+                    let distance = rng.gen_range(wander.distance_bounds.x(), wander.distance_bounds.y());
+                    navigation_point.target = translation.0 + direction * distance;
+                    wander.elapsed = 0.0;
+                    wander.duration = rng.gen_range(wander.duration_bounds.x(), wander.duration_bounds.y());
+                }
+            }
+        })
+}
+
+fn build_navigate_system() -> Box<dyn Schedulable> {
+    SystemBuilder::new("Navigate")
+        .with_query(<(
+            Read<Person>,
+            Write<Translation>,
+            Write<Velocity>,
+            Write<NavigationPoint>,
+        )>::query())
+        .build(move |
+            _, world,
+            _, person_query| {
+            for (_, translation, mut velocity, navigation_point) in person_query.iter(world) {
+                let distance = navigation_point.target - translation.0;
+                if distance.length() > 0.01 {
+                    let direction = distance.normalize();
+                    velocity.value = direction * 2.0;
+                } else {
+                    velocity.value = math::vec3(0.0, 0.0, 0.0);
+                }
+            }
+        })
+}
+
+fn build_move_system() -> Box<dyn Schedulable> {
+    SystemBuilder::new("Move")
+        .read_resource::<Time>()
+        .with_query(<(
+            Write<Translation>,
+            Read<Velocity>,
+        )>::query())
+        .build(move |_, world, time , person_query| {
+            for (mut translation, velocity) in person_query.iter(world) {
+                translation.0 += velocity.value * time.delta_seconds;
+            }
+        })
+}
+
+fn build_print_status_system() -> Box<dyn Schedulable> {
+    let mut elapsed = 0.0;
+    let mut frame_time_total = 0.0;
+    let mut frame_time_count = 0;
+    let frame_time_max = 10;
+    let mut frame_time_values = VecDeque::new();
+    SystemBuilder::new("PrintStatus")
+        .read_resource::<Time>()
+        .with_query(<(
+            Read<Person>,
+        )>::query())
+        .build(move |_, world, time , person_query| {
+            elapsed += time.delta_seconds;
+            frame_time_values.push_front(time.delta_seconds);
+            frame_time_total += time.delta_seconds;
+            frame_time_count += 1;
+            if frame_time_count > frame_time_max {
+                frame_time_count = frame_time_max;
+                frame_time_total -= frame_time_values.pop_back().unwrap();
+            }
+            if elapsed > 1.0 {
+                // println!("fps: {}", if time.delta_seconds == 0.0 { 0.0 } else { 1.0 / time.delta_seconds });
+                if frame_time_count > 0 && frame_time_total > 0.0  {
+                    println!("fps: {}", 1.0 / (frame_time_total / frame_time_count as f32))
+                }
+                println!("peeps: {}", person_query.iter(world).count());
+                elapsed = 0.0;
+            }
+        })
+}
+
+fn create_person(world: &mut World, mesh_handle: Handle<Mesh>, translation: Translation) {
+    world.insert((), vec![
+        (
+            Person{},
+            Wander {
+                duration_bounds: math::vec2(3.0, 10.0),
+                distance_bounds: math::vec2(-50.0, 50.0),
+                elapsed: 0.0,
+                duration: 0.0,
+            },
+            NavigationPoint {
+                target: math::vec3(0.0, 0.0, 0.0),
+            },
+            Velocity {
+                value: math::vec3(0.0, 0.0, 0.0),
+            },
+            Instanced,
+            Material::new(math::vec4(0.5, 0.3, 0.3, 1.0) * random::<f32>()),
+            mesh_handle,
+            LocalToWorld::identity(),
+            translation
+        ),
+    ]);
+} 
\ No newline at end of file
diff --git a/examples/load_model.rs b/examples/load_model.rs
index 2a1dd9a5b4..13c667e845 100644
--- a/examples/load_model.rs
+++ b/examples/load_model.rs
@@ -1,11 +1,8 @@
 use bevy::*;
 
 fn main() {
-    // let universe = Universe::new();
-    // let world = universe.create_world();
-    // let scheduler = SystemScheduler::<ApplicationStage>::new();
-    // asset::load_gltf(get_path("examples/assets/Box.gltf").to_str().unwrap()).unwrap();
     asset::load_gltf("examples/assets/Box.gltf").unwrap();
-
-    // Application::run(universe, world, scheduler);
+    AppBuilder::new()
+        .add_defaults()
+        .run();
 }
\ No newline at end of file
diff --git a/examples/parenting.rs b/examples/parenting.rs
new file mode 100644
index 0000000000..dccf1287e1
--- /dev/null
+++ b/examples/parenting.rs
@@ -0,0 +1,110 @@
+use bevy::{*, render::*, asset::{Asset, AssetStorage}, math::{Mat4, Quat, Vec3}, Schedulable, Parent};
+
+struct Rotator;
+
+fn main() {
+    AppBuilder::new()
+        .add_defaults()
+        .setup(&setup)
+        .run();
+}
+
+fn build_rotator_system() -> Box<dyn Schedulable> {
+    SystemBuilder::new("Rotator")
+        .read_resource::<Time>()
+        .with_query(<(
+            Write<Rotator>,
+            Write<Rotation>,
+        )>::query())
+        .build(move |_, world, time , light_query| {
+            for (_, mut rotation) in light_query.iter(world) {
+                rotation.0 = rotation.0 * Quat::from_rotation_x(3.0 * time.delta_seconds);
+            }
+        })
+}
+
+fn setup(world: &mut World, scheduler: &mut SystemScheduler<AppStage>) {
+    let cube = Mesh::load(MeshType::Cube);
+    let plane = Mesh::load(MeshType::Plane{ size: 10.0 });
+
+    let (cube_handle, plane_handle) = {
+        let mut mesh_storage = world.resources.get_mut::<AssetStorage<Mesh, MeshType>>().unwrap();
+        (mesh_storage.add(cube, "cube"), mesh_storage.add(plane, "plane"))
+    };
+
+    let transform_system_bundle = transform_system_bundle::build(world);
+    scheduler.add_systems(AppStage::Update, transform_system_bundle);
+    scheduler.add_system(AppStage::Update, build_rotator_system());
+
+    // plane
+    world.insert((), vec![
+        (
+            plane_handle.clone(),
+            Material::new(math::vec4(0.1, 0.2, 0.1, 1.0)),
+            LocalToWorld::identity(),
+            Translation::new(0.0, 0.0, -5.0)
+        ),
+    ]);
+    
+    // cube
+    let parent_cube = *world.insert((), vec![
+        (
+            cube_handle.clone(),
+            Material::new(math::vec4(0.5, 0.3, 0.3, 1.0)),
+            LocalToWorld::identity(),
+            Translation::new(0.0, 0.0, 1.0),
+            Rotation::from_euler_angles(0.0, 0.0, 0.0),
+            Rotator,
+        )
+    ]).first().unwrap();
+
+    // cube
+    world.insert((), vec![
+        (
+            cube_handle,
+            Material::new(math::vec4(0.5, 0.3, 0.3, 1.0)),
+            LocalToWorld::identity(),
+            Translation::new(0.0, 0.0, 3.0),
+            Parent(parent_cube),
+            LocalToParent::identity(),
+        )
+    ]);
+
+    // light
+    world.insert((), vec![
+        (
+            Light {
+                color: wgpu::Color {
+                    r: 0.8,
+                    g: 0.8,
+                    b: 0.5,
+                    a: 1.0,
+                },
+                fov: f32::to_radians(60.0),
+                depth: 0.1 .. 50.0,
+                target_view: None,
+            },
+            Material::new(math::vec4(0.5, 0.3, 0.3, 1.0)),
+            LocalToWorld::identity(),
+            Translation::new(4.0, -4.0, 5.0),
+            Rotation::from_euler_angles(0.0, 0.0, 0.0)
+        ),
+    ]);
+
+    // camera
+    world.insert((), vec![
+        (
+            Camera::new(CameraType::Projection {
+                fov: std::f32::consts::PI / 4.0,
+                near: 1.0,
+                far: 1000.0,
+                aspect_ratio: 1.0,
+            }),
+            ActiveCamera,
+            LocalToWorld(Mat4::look_at_rh(
+                Vec3::new(3.0, -15.0, 8.0),
+                Vec3::new(0.0, 0.0, 0.0),
+                Vec3::new(0.0, 0.0, 1.0),)),
+        )
+    ]);
+}
\ No newline at end of file
diff --git a/examples/simple.rs b/examples/simple.rs
index 2e9cfbc40c..05543c2909 100644
--- a/examples/simple.rs
+++ b/examples/simple.rs
@@ -1,200 +1,46 @@
-use bevy::*;
-use bevy::{render::*, asset::{Asset, AssetStorage, Handle}, math::{Mat4, Quat, Vec3}, Schedulable, Parent};
-use rand::{rngs::StdRng, Rng, SeedableRng, random};
-use std::collections::VecDeque;
-
-fn build_wander_system() -> Box<dyn Schedulable> {
-    let mut rng = StdRng::from_entropy();
-    
-    SystemBuilder::new("Wander")
-        .read_resource::<Time>()
-        .with_query(<(
-            Read<Person>,
-            Read<Translation>,
-            Write<Wander>,
-            Write<NavigationPoint>,
-        )>::query())
-        .build(move |
-            _, world,
-            time ,
-            person_query| {
-            for (_, translation, mut wander, mut navigation_point) in person_query.iter(world) {
-                wander.elapsed += time.delta_seconds;
-                if wander.elapsed >= wander.duration {
-                    let direction = math::vec3(
-                        rng.gen_range(-1.0, 1.0),
-                        rng.gen_range(-1.0, 1.0),
-                        rng.gen_range(0.0, 0.001),
-                    ).normalize();
-                    let distance = rng.gen_range(wander.distance_bounds.x(), wander.distance_bounds.y());
-                    navigation_point.target = translation.0 + direction * distance;
-                    wander.elapsed = 0.0;
-                    wander.duration = rng.gen_range(wander.duration_bounds.x(), wander.duration_bounds.y());
-                }
-            }
-        })
-}
-
-fn build_navigate_system() -> Box<dyn Schedulable> {
-    SystemBuilder::new("Navigate")
-        .with_query(<(
-            Read<Person>,
-            Write<Translation>,
-            Write<Velocity>,
-            Write<NavigationPoint>,
-        )>::query())
-        .build(move |
-            _, world,
-            _, person_query| {
-            for (_, translation, mut velocity, navigation_point) in person_query.iter(world) {
-                let distance = navigation_point.target - translation.0;
-                if distance.length() > 0.01 {
-                    let direction = distance.normalize();
-                    velocity.value = direction * 2.0;
-                } else {
-                    velocity.value = math::vec3(0.0, 0.0, 0.0);
-                }
-            }
-        })
-}
-
-fn build_move_system() -> Box<dyn Schedulable> {
-    SystemBuilder::new("Move")
-        .read_resource::<Time>()
-        .with_query(<(
-            Write<Translation>,
-            Read<Velocity>,
-        )>::query())
-        .build(move |_, world, time , person_query| {
-            for (mut translation, velocity) in person_query.iter(world) {
-                translation.0 += velocity.value * time.delta_seconds;
-            }
-        })
-}
-
-fn build_print_status_system() -> Box<dyn Schedulable> {
-    let mut elapsed = 0.0;
-    let mut frame_time_total = 0.0;
-    let mut frame_time_count = 0;
-    let frame_time_max = 10;
-    let mut frame_time_values = VecDeque::new();
-    SystemBuilder::new("PrintStatus")
-        .read_resource::<Time>()
-        .with_query(<(
-            Read<Person>,
-        )>::query())
-        .build(move |_, world, time , person_query| {
-            elapsed += time.delta_seconds;
-            frame_time_values.push_front(time.delta_seconds);
-            frame_time_total += time.delta_seconds;
-            frame_time_count += 1;
-            if frame_time_count > frame_time_max {
-                frame_time_count = frame_time_max;
-                frame_time_total -= frame_time_values.pop_back().unwrap();
-            }
-            if elapsed > 1.0 {
-                // println!("fps: {}", if time.delta_seconds == 0.0 { 0.0 } else { 1.0 / time.delta_seconds });
-                if frame_time_count > 0 && frame_time_total > 0.0  {
-                    println!("fps: {}", 1.0 / (frame_time_total / frame_time_count as f32))
-                }
-                println!("peeps: {}", person_query.iter(world).count());
-                elapsed = 0.0;
-            }
-        })
-}
-
-fn build_spawner_system(world: &mut World) -> Box<dyn Schedulable> {
-    let mesh_handle = {
-        let mesh_storage = world.resources.get_mut::<AssetStorage<Mesh, MeshType>>().unwrap();
-        mesh_storage.get_named("cube").unwrap()
-    };
-
-    let duration = 0.5;
-    let mut elapsed = duration;
-    let batch_size = 100;
-
-    SystemBuilder::new("Spawner")
-        .read_resource::<Time>()
-        .with_query(<(
-            Read<Person>,
-        )>::query())
-        .build(move |command_buffer, _, time , _| {
-            elapsed += time.delta_seconds;
-            if elapsed > duration {
-                for _ in 0..batch_size {
-                    spawn_person(command_buffer, mesh_handle.clone());
-                }
-                elapsed = 0.0;
-            }
-        })
-}
-
-fn build_light_rotator_system() -> Box<dyn Schedulable> {
-    SystemBuilder::new("LightRotator")
-        .read_resource::<Time>()
-        .with_query(<(
-            Write<Light>,
-            Write<Rotation>,
-        )>::query())
-        .build(move |_, world, time , light_query| {
-            for (_, mut rotation) in light_query.iter(world) {
-                rotation.0 = rotation.0 * Quat::from_rotation_x(3.0 * time.delta_seconds);
-            }
-        })
-}
-
-struct Person {
-}
-
-struct Velocity {
-    pub value: math::Vec3,
-}
-
-struct NavigationPoint {
-    pub target: math::Vec3,
-}
-
-struct Wander {
-    pub duration_bounds: math::Vec2,
-    pub distance_bounds: math::Vec2,
-    pub duration: f32,
-    pub elapsed: f32,
-}
+use bevy::{*, render::*, asset::{Asset, AssetStorage}, math::{Mat4, Vec3}};
 
 fn main() {
-    let universe = Universe::new();
-    let mut world = universe.create_world();
-    let mut scheduler = SystemScheduler::<ApplicationStage>::new();
+    AppBuilder::new()
+        .add_defaults()
+        .setup(&setup)
+        .run();
+}
 
+fn setup(world: &mut World, scheduler: &mut SystemScheduler<AppStage>) {
     let cube = Mesh::load(MeshType::Cube);
-    let plane = Mesh::load(MeshType::Plane{ size: 24.5 });
-    let mut mesh_storage = AssetStorage::<Mesh, MeshType>::new();
+    let plane = Mesh::load(MeshType::Plane{ size: 10.0 });
 
-    let _cube_handle = mesh_storage.add(cube, "cube");
-    let plane_handle = mesh_storage.add(plane, "plane");
-    world.resources.insert(mesh_storage);
+    let (cube_handle, plane_handle) = {
+        let mut mesh_storage = world.resources.get_mut::<AssetStorage<Mesh, MeshType>>().unwrap();
+        (mesh_storage.add(cube, "cube"), mesh_storage.add(plane, "plane"))
+    };
 
-    let transform_system_bundle = transform_system_bundle::build(&mut world);
-    scheduler.add_systems(ApplicationStage::Update, transform_system_bundle);
-    scheduler.add_system(ApplicationStage::Update, build_wander_system());
-    scheduler.add_system(ApplicationStage::Update, build_navigate_system());
-    scheduler.add_system(ApplicationStage::Update, build_move_system());
-    // scheduler.add_system(ApplicationStage::Update, build_light_rotator_system());
-    // scheduler.add_system(ApplicationStage::Update, build_spawner_system(&mut world));
-    scheduler.add_system(ApplicationStage::Update, build_print_status_system());
+    let transform_system_bundle = transform_system_bundle::build(world);
+    scheduler.add_systems(AppStage::Update, transform_system_bundle);
 
-    // world.insert((), vec![
-    //     // plane
-    //     (
-    //         Material::new(math::vec4(0.1, 0.2, 0.1, 1.0)),
-    //         plane_handle.clone(),
-    //         LocalToWorld::identity(),
-    //         Translation::new(0.0, 0.0, 0.0)
-    //     ),
-    // ]);
+    // plane
+    world.insert((), vec![
+        (
+            plane_handle.clone(),
+            Material::new(math::vec4(0.1, 0.2, 0.1, 1.0)),
+            LocalToWorld::identity(),
+            Translation::new(0.0, 0.0, 0.0)
+        ),
+    ]);
+    
+    // cube
+    world.insert((), vec![
+        (
+            cube_handle,
+            Material::new(math::vec4(0.5, 0.3, 0.3, 1.0)),
+            LocalToWorld::identity(),
+            Translation::new(0.0, 0.0, 1.0)
+        )
+    ]);
 
-    let x = *world.insert((), vec![
-        // lights
+    // light
+    world.insert((), vec![
         (
             Light {
                 color: wgpu::Color {
@@ -208,45 +54,14 @@ fn main() {
                 target_view: None,
             },
             Material::new(math::vec4(0.5, 0.3, 0.3, 1.0)),
-            // _cube_handle.clone(),
             LocalToWorld::identity(),
             Translation::new(4.0, -4.0, 5.0),
             Rotation::from_euler_angles(0.0, 0.0, 0.0)
         ),
-        // (
-        //     Light {
-        //         color: wgpu::Color {
-        //             r: 1.0,
-        //             g: 0.5,
-        //             b: 0.5,
-        //             a: 1.0,
-        //         },
-        //         fov: f32::to_radians(45.0),
-        //         depth: 1.0 .. 20.0,
-        //         target_view: None,
-        //     },
-        //     // Material::new(math::vec4(0.5, 0.3, 0.3, 1.0) * random::<f32>()),
-        //     // cube_handle.clone(),
-        //     LocalToWorld::identity(),
-        //     Translation::new(-5.0, 7.0, 10.0)
-        // ),
-    ]).first().unwrap();
-
-    // world.insert((), vec![
-    //     (
-    //         Material::new(math::vec4(1.0, 1.0, 1.0, 1.0)),
-    //         _cube_handle.clone(),
-    //         LocalToWorld::identity(),
-    //         Translation::new(0.0, 0.0, 3.0),
-    //         Scale(1.0),
-    //         Parent(x),
-    //         LocalToParent::identity(),
-    //     )
-    // ]);
+    ]);
 
+    // camera
     world.insert((), vec![
-        
-        // camera
         (
             Camera::new(CameraType::Projection {
                 fov: std::f32::consts::PI / 4.0,
@@ -256,114 +71,9 @@ fn main() {
             }),
             ActiveCamera,
             LocalToWorld(Mat4::look_at_rh(
-                Vec3::new(6.0, -40.0, 20.0),
+                Vec3::new(3.0, -8.0, 5.0),
                 Vec3::new(0.0, 0.0, 0.0),
                 Vec3::new(0.0, 0.0, 1.0),)),
-            // Translation::new(0.0, 0.0, 0.0),
         )
     ]);
-
-    world.insert((), vec![
-        
-        // camera
-        (
-            Camera::new(CameraType::Orthographic {
-                left: 0.0,
-                right: 0.0,
-                bottom: 0.0,
-                top: 0.0,
-                near: 0.0,
-                far: 1.0,
-            }),
-            ActiveCamera2d,
-        )
-    ]);
-
-    world.insert((), vec![
-        (
-            Rect {
-                position: math::vec2(75.0, 75.0),
-                dimensions: math::vec2(100.0, 100.0),
-                color: math::vec4(0.0, 1.0, 0.0, 1.0),
-            },
-        )
-    ]);
-
-    world.insert((), vec![
-        (
-            Rect {
-                position: math::vec2(50.0, 50.0),
-                dimensions: math::vec2(100.0, 100.0),
-                color: math::vec4(1.0, 0.0, 0.0, 1.0),
-            },
-        )
-    ]);
-
-    world.insert((), vec![
-        (
-            Rect {
-                position: math::vec2(100.0, 100.0),
-                dimensions: math::vec2(100.0, 100.0),
-                color: math::vec4(0.0, 0.0, 1.0, 1.0),
-            },
-        )
-    ]);
-
-    let mut rng = StdRng::from_entropy();
-    for _ in 0 .. 5 {
-        create_person(&mut world, _cube_handle.clone(),
-            Translation::new(rng.gen_range(-50.0, 50.0), 0.0, rng.gen_range(-50.0, 50.0)));
-    }
-
-    Application::run(universe, world, scheduler);
-}
-
-fn spawn_person(command_buffer: &mut CommandBuffer, mesh_handle: Handle<Mesh>) {
-    command_buffer.insert((), vec![
-        (
-            Person{},
-            Wander {
-                duration_bounds: math::vec2(3.0, 10.0),
-                distance_bounds: math::vec2(-50.0, 50.0),
-                elapsed: 0.0,
-                duration: 0.0,
-            },
-            NavigationPoint {
-                target: math::vec3(0.0, 0.0, 0.0),
-            },
-            Velocity {
-                value: math::vec3(0.0, 0.0, 0.0),
-            },
-            Instanced,
-            Material::new(math::vec4(0.5, 0.3, 0.3, 1.0) * random::<f32>()),
-            mesh_handle.clone(),
-            LocalToWorld::identity(),
-            Translation::new(0.0, 0.0, 1.0)
-        ),
-    ]);
-}
-
-fn create_person(world: &mut World, mesh_handle: Handle<Mesh>, translation: Translation) {
-    world.insert((), vec![
-        (
-            Person{},
-            Wander {
-                duration_bounds: math::vec2(3.0, 10.0),
-                distance_bounds: math::vec2(-50.0, 50.0),
-                elapsed: 0.0,
-                duration: 0.0,
-            },
-            NavigationPoint {
-                target: math::vec3(0.0, 0.0, 0.0),
-            },
-            Velocity {
-                value: math::vec3(0.0, 0.0, 0.0),
-            },
-            Instanced,
-            Material::new(math::vec4(0.5, 0.3, 0.3, 1.0) * random::<f32>()),
-            mesh_handle,
-            LocalToWorld::identity(),
-            translation
-        ),
-    ]);
-} 
\ No newline at end of file
+}
\ No newline at end of file
diff --git a/examples/ui.rs b/examples/ui.rs
new file mode 100644
index 0000000000..b91911195c
--- /dev/null
+++ b/examples/ui.rs
@@ -0,0 +1,108 @@
+use bevy::{*, render::*, asset::{Asset, AssetStorage}, math::{Mat4, Vec3}};
+
+fn main() {
+    AppBuilder::new()
+        .add_defaults()
+        .setup(&setup)
+        .run();
+}
+
+fn setup(world: &mut World, scheduler: &mut SystemScheduler<AppStage>) {
+    let cube = Mesh::load(MeshType::Cube);
+    let cube_handle = {
+        let mut mesh_storage = world.resources.get_mut::<AssetStorage<Mesh, MeshType>>().unwrap();
+        mesh_storage.add(cube, "cube")
+    };
+
+    let transform_system_bundle = transform_system_bundle::build(world);
+    scheduler.add_systems(AppStage::Update, transform_system_bundle);
+
+    world.insert((), vec![
+        (
+            cube_handle,
+            LocalToWorld::identity(),
+            Material::new(math::vec4(0.5, 0.3, 0.3, 1.0)),
+        )
+    ]);
+
+    world.insert((), vec![
+        (
+            Light {
+                color: wgpu::Color {
+                    r: 0.8,
+                    g: 0.8,
+                    b: 0.5,
+                    a: 1.0,
+                },
+                fov: f32::to_radians(60.0),
+                depth: 0.1 .. 50.0,
+                target_view: None,
+            },
+            LocalToWorld::identity(),
+            Translation::new(4.0, -4.0, 5.0),
+            Rotation::from_euler_angles(0.0, 0.0, 0.0)
+        ),
+    ]);
+
+    world.insert((), vec![
+        // camera
+        (
+            Camera::new(CameraType::Projection {
+                fov: std::f32::consts::PI / 4.0,
+                near: 1.0,
+                far: 1000.0,
+                aspect_ratio: 1.0,
+            }),
+            ActiveCamera,
+            LocalToWorld(Mat4::look_at_rh(
+                Vec3::new(3.0, -5.0, 3.0),
+                Vec3::new(0.0, 0.0, 0.0),
+                Vec3::new(0.0, 0.0, 1.0),)),
+        )
+    ]);
+
+    world.insert((), vec![
+        // camera
+        (
+            Camera::new(CameraType::Orthographic {
+                left: 0.0,
+                right: 0.0,
+                bottom: 0.0,
+                top: 0.0,
+                near: 0.0,
+                far: 1.0,
+            }),
+            ActiveCamera2d,
+        )
+    ]);
+
+    world.insert((), vec![
+        (
+            Rect {
+                position: math::vec2(75.0, 75.0),
+                dimensions: math::vec2(100.0, 100.0),
+                color: math::vec4(0.0, 1.0, 0.0, 1.0),
+            },
+        )
+    ]);
+
+    world.insert((), vec![
+        (
+            Rect {
+                position: math::vec2(50.0, 50.0),
+                dimensions: math::vec2(100.0, 100.0),
+                color: math::vec4(1.0, 0.0, 0.0, 1.0),
+            },
+        )
+    ]);
+
+    world.insert((), vec![
+        (
+            Rect {
+                position: math::vec2(100.0, 100.0),
+                dimensions: math::vec2(100.0, 100.0),
+                color: math::vec4(0.0, 0.0, 1.0, 1.0),
+            },
+        )
+    ]);
+}
\ No newline at end of file
diff --git a/src/app/app_builder.rs b/src/app/app_builder.rs
new file mode 100644
index 0000000000..922ac5dcb0
--- /dev/null
+++ b/src/app/app_builder.rs
@@ -0,0 +1,55 @@
+use crate::{App, asset::AssetStorage, legion::prelude::{World, SystemScheduler}, render::{*, passes::*}, AppStage, Time};
+
+pub struct AppBuilder {
+    pub app: App,
+}
+
+impl AppBuilder {
+    pub fn new() -> Self {
+        let world = World::new();
+        let scheduler = SystemScheduler::<AppStage>::new();
+        AppBuilder {
+            app: App::new(world, scheduler),
+        }
+    }
+
+    pub fn build(self) -> App {
+        self.app
+    }
+
+    pub fn run(self) {
+        self.app.run();
+    }
+
+    pub fn setup(mut self, setup: &dyn Fn(&mut World, &mut SystemScheduler<AppStage>)) -> Self {
+        setup(&mut self.app.world, &mut self.app.scheduler);
+        self
+    }
+
+    pub fn add_default_passes(mut self) -> Self {
+        self.app.render_graph.add_render_resource_manager(Box::new(render_resources::MaterialResourceManager));
+        self.app.render_graph.add_render_resource_manager(Box::new(render_resources::LightResourceManager::new(10)));
+        self.app.render_graph.add_render_resource_manager(Box::new(render_resources::GlobalResourceManager));
+        self.app.render_graph.add_render_resource_manager(Box::new(render_resources::Global2dResourceManager));
+
+        let depth_format = wgpu::TextureFormat::Depth32Float;
+        self.app.render_graph.set_pass("forward", Box::new(ForwardPass::new(depth_format)));
+        self.app.render_graph.set_pipeline("forward", "forward", Box::new(ForwardPipeline::new()));
+        self.app.render_graph.set_pipeline("forward", "forward_instanced", Box::new(ForwardInstancedPipeline::new(depth_format)));
+        self.app.render_graph.set_pipeline("forward", "ui", Box::new(UiPipeline::new()));
+
+        self
+    }
+
+    pub fn add_default_resources(mut self) -> Self {
+        self.app.world.resources.insert(Time::new());
+        self.app.world.resources.insert(AssetStorage::<Mesh, MeshType>::new());
+        self
+    }
+
+    pub fn add_defaults(self) -> Self {
+        self
+            .add_default_resources()
+            .add_default_passes()
+    }
+}
\ No newline at end of file
diff --git a/src/app/app_stage.rs b/src/app/app_stage.rs
new file mode 100644
index 0000000000..5ef10ce467
--- /dev/null
+++ b/src/app/app_stage.rs
@@ -0,0 +1,18 @@
+use legion::schedule::Stage;
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
+pub enum AppStage {
+    Update,
+    Render,
+}
+
+impl Stage for AppStage {}
+
+impl std::fmt::Display for AppStage {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            AppStage::Update => write!(f, "update"),
+            AppStage::Render => write!(f, "draw"),
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/application.rs b/src/app/mod.rs
similarity index 64%
rename from src/application.rs
rename to src/app/mod.rs
index 6e78df20e6..7eeae1ed20 100644
--- a/src/application.rs
+++ b/src/app/mod.rs
@@ -1,3 +1,9 @@
+mod app_stage;
+mod app_builder;
+
+pub use app_stage::AppStage;
+pub use app_builder::AppBuilder;
+
 use winit::{
     event,
     event::WindowEvent,
@@ -7,30 +13,27 @@ use winit::{
 
 use legion::prelude::*;
 
-use crate::{render::*, render::passes::*, ApplicationStage, Time};
+use crate::{render::*, Time};
 
-pub struct Application
+pub struct App
 {
-    pub universe: Universe,
     pub world: World,
-    pub window: Window,
+    pub window: Option<Window>,
     pub render_graph: RenderGraph,
-    pub scheduler: SystemScheduler<ApplicationStage>,
+    pub swap_chain: Option<wgpu::SwapChain>,
+    pub scheduler: SystemScheduler<AppStage>,
 }
 
-impl Application {
-    fn add_default_passes(&mut self) {
-        self.render_graph.add_render_resource_manager(Box::new(render_resources::MaterialResourceManager));
-        self.render_graph.add_render_resource_manager(Box::new(render_resources::LightResourceManager::new(10)));
-        self.render_graph.add_render_resource_manager(Box::new(render_resources::GlobalResourceManager));
-        self.render_graph.add_render_resource_manager(Box::new(render_resources::Global2dResourceManager));
-
-        let depth_format = wgpu::TextureFormat::Depth32Float;
-        self.render_graph.set_pass("forward", Box::new(ForwardPass::new(depth_format)));
-        self.render_graph.set_pipeline("forward", "forward", Box::new(ForwardPipeline::new()));
-        self.render_graph.set_pipeline("forward", "forward_instanced", Box::new(ForwardInstancedPipeline::new(depth_format)));
-        self.render_graph.set_pipeline("forward", "ui", Box::new(UiPipeline::new()));
-    }
+impl App {
+    pub fn new(world: World, scheduler: SystemScheduler<AppStage>) -> App {
+        App {
+            world: world,
+            scheduler: scheduler,
+            render_graph: RenderGraph::new(),
+            swap_chain: None,
+            window: None,
+        }
+    }    
 
     fn update(&mut self) {
         {
@@ -47,7 +50,7 @@ impl Application {
 
     fn resize(&mut self, width: u32, height: u32)
     {
-        self.render_graph.resize(width, height, &mut self.world);
+        self.swap_chain = Some(self.render_graph.resize(width, height, &mut self.world));
     }
 
     fn handle_event(&mut self, _: WindowEvent)
@@ -56,11 +59,10 @@ impl Application {
 
     fn render(&mut self)
     {
-        self.render_graph.render(&mut self.world);
+        self.render_graph.render(&mut self.world, self.swap_chain.as_mut().unwrap());
     }
 
-    #[allow(dead_code)]
-    pub fn run(universe: Universe, mut world: World, system_scheduler: SystemScheduler<ApplicationStage>) {
+    pub fn run(mut self) {
         env_logger::init();
         let event_loop = EventLoop::new();
         log::info!("Initializing the window...");
@@ -80,14 +82,14 @@ impl Application {
             limits: wgpu::Limits::default(),
         });
 
-        let (window, hidpi_factor, size, surface) = {
+        let (window, size, surface) = {
             let window = winit::window::Window::new(&event_loop).unwrap();
             window.set_title("bevy");
             window.set_inner_size((1280, 720).into());
             let hidpi_factor = window.hidpi_factor();
             let size = window.inner_size().to_physical(hidpi_factor);
             let surface = wgpu::Surface::create(&window);
-            (window, hidpi_factor, size, surface)
+            (window, size, surface)
         };
     
         let swap_chain_descriptor = wgpu::SwapChainDescriptor {
@@ -98,21 +100,12 @@ impl Application {
             present_mode: wgpu::PresentMode::Vsync,
         };
         let swap_chain = device.create_swap_chain(&surface, &swap_chain_descriptor);
-        
-        world.resources.insert(Time::new());
 
         log::info!("Initializing the example...");
-        let render_graph = RenderGraph::new(device, swap_chain_descriptor, swap_chain, queue, surface);
-        let mut app = Application {
-            universe,
-            world,
-            window,
-            render_graph,
-            scheduler: system_scheduler,
-        };
+        self.render_graph.initialize(&mut self.world, device, swap_chain_descriptor, queue, surface);
+        self.window = Some(window);
+        self.swap_chain = Some(swap_chain);
 
-        app.add_default_passes();
-        app.render_graph.initialize(&mut app.world);
     
         log::info!("Entering render loop...");
         event_loop.run(move |event, _, control_flow| {
@@ -126,11 +119,12 @@ impl Application {
                     event: WindowEvent::Resized(size),
                     ..
                 } => {
+                    let hidpi_factor = self.window.as_ref().unwrap().hidpi_factor();
                     let physical = size.to_physical(hidpi_factor);
                     log::info!("Resizing to {:?}", physical);
                     let width = physical.width.round() as u32;
                     let height = physical.height.round() as u32;
-                    app.resize(width, height);
+                    self.resize(width, height);
                 }
                 event::Event::WindowEvent { event, .. } => match event {
                     WindowEvent::KeyboardInput {
@@ -146,11 +140,11 @@ impl Application {
                         *control_flow = ControlFlow::Exit;
                     }
                     _ => {
-                        app.handle_event(event);
+                        self.handle_event(event);
                     }
                 },
                 event::Event::EventsCleared => {
-                    app.update();
+                    self.update();
                 }
                 _ => (),
             }
diff --git a/src/core/mod.rs b/src/core/mod.rs
index e8cb882c4a..3e40bc8327 100644
--- a/src/core/mod.rs
+++ b/src/core/mod.rs
@@ -1,21 +1,2 @@
-use legion::schedule::Stage;
-
 pub mod time;
-pub use time::Time;
-
-#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
-pub enum ApplicationStage {
-    Update,
-    Render,
-}
-
-impl Stage for ApplicationStage {}
-
-impl std::fmt::Display for ApplicationStage {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        match self {
-            ApplicationStage::Update => write!(f, "update"),
-            ApplicationStage::Render => write!(f, "draw"),
-        }
-    }
-}
+pub use time::Time;
\ No newline at end of file
diff --git a/src/lib.rs b/src/lib.rs
index 8b02414242..c7ea840a42 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,10 +1,10 @@
 pub mod render;
 pub mod asset;
-mod application;
+mod app;
 mod vertex;
 mod core;
 
-pub use application::Application;
+pub use app::{App, AppStage, AppBuilder};
 pub use crate::core::*;
 
 pub use wgpu;
diff --git a/src/render/passes/forward_instanced/mod.rs b/src/render/passes/forward_instanced/mod.rs
index 3801de7ec8..6c3f578e3b 100644
--- a/src/render/passes/forward_instanced/mod.rs
+++ b/src/render/passes/forward_instanced/mod.rs
@@ -24,6 +24,10 @@ impl ForwardInstancedPipeline {
     fn create_instance_buffer_infos(device: &Device, world: &World) -> Vec<InstanceBufferInfo> {
         let mut entities = <(Read<Material>, Read<LocalToWorld>, Read<Handle<Mesh>>, Read<Instanced>)>::query();
         let entities_count = entities.iter_immutable(world).count();
+        if entities_count == 0 {
+            return Vec::new();
+        }
+
         let size = mem::size_of::<SimpleMaterialUniforms>();
 
         // TODO: use a staging buffer for more efficient gpu reads
diff --git a/src/render/passes/ui/mod.rs b/src/render/passes/ui/mod.rs
index 56a88f13cc..607b6d838f 100644
--- a/src/render/passes/ui/mod.rs
+++ b/src/render/passes/ui/mod.rs
@@ -33,6 +33,10 @@ impl UiPipeline {
         let mut rect_query = <Read<Rect>>::query();
         let rect_count = rect_query.iter_immutable(world).count();
 
+        if rect_count == 0 {
+            return Vec::new();
+        }
+
         let mut data = Vec::with_capacity(rect_count);
         // TODO: this probably isn't the best way to handle z-ordering
         let mut z = 0.9999;
diff --git a/src/render/render_graph/mod.rs b/src/render/render_graph/mod.rs
index c53e3a10dd..7f22bdcf15 100644
--- a/src/render/render_graph/mod.rs
+++ b/src/render/render_graph/mod.rs
@@ -11,12 +11,11 @@ use std::collections::HashMap;
 use legion::world::World;
 
 pub struct RenderGraph {
-    pub data: RenderGraphData,
+    pub data: Option<RenderGraphData>,
     passes: HashMap<String, Box<dyn Pass>>,
     pipelines: HashMap<String, Box<dyn Pipeline>>,
     pass_pipelines: HashMap<String, Vec<String>>,
     render_resource_managers: Vec<Box<dyn RenderResourceManager>>,
-    pub swap_chain: wgpu::SwapChain, // TODO: this is weird
 }
 
 pub struct RenderGraphData {
@@ -77,53 +76,56 @@ impl RenderGraphData {
 }
 
 impl RenderGraph {
-    pub fn new(device: wgpu::Device, swap_chain_descriptor: wgpu::SwapChainDescriptor, swap_chain: wgpu::SwapChain, queue: wgpu::Queue, surface: wgpu::Surface) -> Self {
+    pub fn new() -> Self {
         RenderGraph {
             passes: HashMap::new(),
             pipelines: HashMap::new(),
-            swap_chain,
             pass_pipelines: HashMap::new(),
             render_resource_managers: Vec::new(),
-            data: RenderGraphData::new(device, swap_chain_descriptor, queue, surface),
+            data: None,
         }
     }
 
-    pub fn initialize(&mut self, world: &mut World) {
+    pub fn initialize(&mut self, world: &mut World, device: wgpu::Device, swap_chain_descriptor: wgpu::SwapChainDescriptor, queue: wgpu::Queue, surface: wgpu::Surface) {
+        let mut data = RenderGraphData::new(device, swap_chain_descriptor, queue, surface);
         for render_resource_manager in self.render_resource_managers.iter_mut() {
-            render_resource_manager.initialize(&mut self.data, world);
+            render_resource_manager.initialize(&mut data, world);
         }
 
         for pass in self.passes.values_mut() {
-            pass.initialize(&mut self.data);
+            pass.initialize(&mut data);
         }
         
         for pipeline in self.pipelines.values_mut() {
-            pipeline.initialize(&mut self.data, world);
+            pipeline.initialize(&mut data, world);
         }
+
+        self.data = Some(data);
     }
 
-    pub fn render(&mut self, world: &mut World) {
-        let frame = self.swap_chain
+    pub fn render(&mut self, world: &mut World, swap_chain: &mut wgpu::SwapChain) {
+        let frame = swap_chain
             .get_next_texture()
             .expect("Timeout when acquiring next swap chain texture");
 
+        let data = self.data.as_mut().unwrap();
         let mut encoder =
-            self.data.device.create_command_encoder(&wgpu::CommandEncoderDescriptor { todo: 0 });
+            data.device.create_command_encoder(&wgpu::CommandEncoderDescriptor { todo: 0 });
 
         for render_resource_manager in self.render_resource_managers.iter_mut() {
-            render_resource_manager.update(&mut self.data, &mut encoder, world);
+            render_resource_manager.update(data, &mut encoder, world);
         }
 
         for (pass_name, pass) in self.passes.iter_mut() {
             loop {
-                let render_pass = pass.begin(&mut self.data, world, &mut encoder, &frame);
+                let render_pass = pass.begin(data, world, &mut encoder, &frame);
                 if let Some(mut render_pass) = render_pass {
                     // TODO: assign pipelines to specific passes
                     if let Some(pipeline_names)  = self.pass_pipelines.get(pass_name) {
                         for pipeline_name in pipeline_names.iter() {
                             let pipeline = self.pipelines.get_mut(pipeline_name).unwrap();
                             render_pass.set_pipeline(pipeline.get_pipeline());
-                            pipeline.render(&mut self.data, &mut render_pass, &frame, world);
+                            pipeline.render(data, &mut render_pass, &frame, world);
                         }
                     }
 
@@ -135,32 +137,33 @@ impl RenderGraph {
         }
 
         let command_buffer = encoder.finish();
-        self.data.queue.submit(&[command_buffer]);
+        data.queue.submit(&[command_buffer]);
     }
 
-    pub fn resize(&mut self, width: u32, height: u32, world: &mut World) {
-        self.data.swap_chain_descriptor.width = width;
-        self.data.swap_chain_descriptor.height = height;
-        self.swap_chain = self.data.device.create_swap_chain(&self.data.surface, &self.data.swap_chain_descriptor);
+    pub fn resize(&mut self, width: u32, height: u32, world: &mut World) -> wgpu::SwapChain {
+        let data = self.data.as_mut().unwrap();
+        data.swap_chain_descriptor.width = width;
+        data.swap_chain_descriptor.height = height;
+        let swap_chain = data.device.create_swap_chain(&data.surface, &data.swap_chain_descriptor);
         let mut encoder =
-            self.data.device.create_command_encoder(&wgpu::CommandEncoderDescriptor { todo: 0 });
+            data.device.create_command_encoder(&wgpu::CommandEncoderDescriptor { todo: 0 });
 
         for render_resource_manager in self.render_resource_managers.iter_mut() {
-            render_resource_manager.resize(&mut self.data, &mut encoder, world);
+            render_resource_manager.resize(data, &mut encoder, world);
         }
 
         let command_buffer = encoder.finish();
 
         for pass in self.passes.values_mut() {
-            pass.resize(&mut self.data);
+            pass.resize(data);
         }
 
         for pipeline in self.pipelines.values_mut() {
-            pipeline.resize(&mut self.data);
+            pipeline.resize(data);
         }
 
-        self.data.queue.submit(&[command_buffer]);
-
+        data.queue.submit(&[command_buffer]);
+        swap_chain
     }
 
     pub fn add_render_resource_manager(&mut self, render_resource_manager: Box<dyn RenderResourceManager>) {
diff --git a/src/render/render_resources/light_resource_manager.rs b/src/render/render_resources/light_resource_manager.rs
index 6cc754ef5f..8fe53c0d21 100644
--- a/src/render/render_resources/light_resource_manager.rs
+++ b/src/render/render_resources/light_resource_manager.rs
@@ -42,6 +42,10 @@ impl RenderResourceManager for LightResourceManager {
             let mut light_query = <(Read<Light>, Read<LocalToWorld>, Read<Translation>)>::query();
             let light_count = light_query.iter(world).count();
 
+            if light_count == 0 {
+                return;
+            }
+
             self.lights_are_dirty = false;
             let size = mem::size_of::<LightRaw>();
             let total_size = size * light_count;
diff --git a/src/render/render_resources/material_resource_manager.rs b/src/render/render_resources/material_resource_manager.rs
index 6f273b9dab..2209144f63 100644
--- a/src/render/render_resources/material_resource_manager.rs
+++ b/src/render/render_resources/material_resource_manager.rs
@@ -26,6 +26,10 @@ impl RenderResourceManager for MaterialResourceManager {
         let mut entities = <(Write<Material>, Read<LocalToWorld>)>::query()
             .filter(!component::<Instanced>());
         let entities_count = entities.iter(world).count();
+        if entities_count == 0 {
+            return;
+        }
+
         let size = mem::size_of::<MaterialUniforms>();
         let temp_buf_data = render_graph.device
             .create_buffer_mapped(entities_count * size, wgpu::BufferUsage::COPY_SRC);