3D OrthographicProjection improvements + new example (#1361)

* use `length_squared` for visible entities

* ortho projection 2d/3d different depth calculation

* use ScalingMode::FixedVertical for 3d ortho

* new example: 3d orthographic

Cargo.toml

@@ -121,6 +121,10 @@ path = "examples/3d/load_gltf.rs"
 name = "msaa"
 path = "examples/3d/msaa.rs"
 
+[[example]]
+name = "orthographic"
+path = "examples/3d/orthographic.rs"
+
 [[example]]
 name = "parenting"
 path = "examples/3d/parenting.rs"

crates/bevy_render/src/camera/camera.rs

@@ -2,9 +2,10 @@ use super::CameraProjection;
 use bevy_app::prelude::EventReader;
 use bevy_ecs::{Added, Component, Entity, Query, QuerySet, Res};
 use bevy_math::{Mat4, Vec2, Vec3};
-use bevy_reflect::{Reflect, ReflectComponent};
+use bevy_reflect::{Reflect, ReflectComponent, ReflectDeserialize};
 use bevy_transform::components::GlobalTransform;
 use bevy_window::{WindowCreated, WindowId, WindowResized, Windows};
+use serde::{Deserialize, Serialize};
 
 #[derive(Default, Debug, Reflect)]
 #[reflect(Component)]
@@ -17,9 +18,12 @@ pub struct Camera {
     pub depth_calculation: DepthCalculation,
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone, Copy, Reflect, Serialize, Deserialize)]
+#[reflect_value(Serialize, Deserialize)]
 pub enum DepthCalculation {
+    /// Pythagorean distance; works everywhere, more expensive to compute.
     Distance,
+    /// Optimization for 2D; assuming the camera points towards -Z.
     ZDifference,
 }
 

crates/bevy_render/src/camera/projection.rs

@@ -77,6 +77,7 @@ pub struct OrthographicProjection {
     pub window_origin: WindowOrigin,
     pub scaling_mode: ScalingMode,
     pub scale: f32,
+    pub depth_calculation: DepthCalculation,
 }
 
 impl CameraProjection for OrthographicProjection {
@@ -140,7 +141,7 @@ impl CameraProjection for OrthographicProjection {
     }
 
     fn depth_calculation(&self) -> DepthCalculation {
-        DepthCalculation::ZDifference
+        self.depth_calculation
     }
 }
 
@@ -156,6 +157,7 @@ impl Default for OrthographicProjection {
             window_origin: WindowOrigin::Center,
             scaling_mode: ScalingMode::WindowSize,
             scale: 1.0,
+            depth_calculation: DepthCalculation::Distance,
         }
     }
 }

crates/bevy_render/src/camera/visible_entities.rs

@@ -231,7 +231,7 @@ pub fn visible_entities_system(
                 // smaller distances are sorted to lower indices by using the distance from the camera
                 FloatOrd(match camera.depth_calculation {
                     DepthCalculation::ZDifference => camera_position.z - position.z,
-                    DepthCalculation::Distance => (camera_position - position).length(),
+                    DepthCalculation::Distance => (camera_position - position).length_squared(),
                 })
             } else {
                 let order = FloatOrd(no_transform_order);

crates/bevy_render/src/entity.rs

@@ -1,5 +1,8 @@
 use crate::{
-    camera::{Camera, OrthographicProjection, PerspectiveProjection, VisibleEntities},
+    camera::{
+        Camera, DepthCalculation, OrthographicProjection, PerspectiveProjection, ScalingMode,
+        VisibleEntities,
+    },
     pipeline::RenderPipelines,
     prelude::Visible,
     render_graph::base,
@@ -92,6 +95,7 @@ impl OrthographicCameraBundle {
             },
             orthographic_projection: OrthographicProjection {
                 far,
+                depth_calculation: DepthCalculation::ZDifference,
                 ..Default::default()
             },
             visible_entities: Default::default(),
@@ -106,7 +110,11 @@ impl OrthographicCameraBundle {
                 name: Some(base::camera::CAMERA_3D.to_string()),
                 ..Default::default()
             },
-            orthographic_projection: Default::default(),
+            orthographic_projection: OrthographicProjection {
+                scaling_mode: ScalingMode::FixedVertical,
+                depth_calculation: DepthCalculation::Distance,
+                ..Default::default()
+            },
             visible_entities: Default::default(),
             transform: Default::default(),
             global_transform: Default::default(),

crates/bevy_ui/src/entity.rs

@@ -7,7 +7,7 @@ use crate::{
 use bevy_asset::Handle;
 use bevy_ecs::Bundle;
 use bevy_render::{
-    camera::{Camera, OrthographicProjection, VisibleEntities, WindowOrigin},
+    camera::{Camera, DepthCalculation, OrthographicProjection, VisibleEntities, WindowOrigin},
     draw::Draw,
     mesh::Mesh,
     pipeline::{RenderPipeline, RenderPipelines},
@@ -185,6 +185,7 @@ impl Default for UiCameraBundle {
             orthographic_projection: OrthographicProjection {
                 far,
                 window_origin: WindowOrigin::BottomLeft,
+                depth_calculation: DepthCalculation::ZDifference,
                 ..Default::default()
             },
             visible_entities: Default::default(),

examples/3d/orthographic.rs

@@ -0,0 +1,62 @@
+use bevy::prelude::*;
+
+fn main() {
+    App::build()
+        .insert_resource(Msaa { samples: 4 })
+        .add_plugins(DefaultPlugins)
+        .add_startup_system(setup.system())
+        .run();
+}
+
+/// set up a simple 3D scene
+fn setup(
+    commands: &mut Commands,
+    mut meshes: ResMut<Assets<Mesh>>,
+    mut materials: ResMut<Assets<StandardMaterial>>,
+) {
+    // set up the camera
+    let mut camera = OrthographicCameraBundle::new_3d();
+    camera.orthographic_projection.scale = 3.0;
+    camera.transform = Transform::from_xyz(5.0, 5.0, 5.0).looking_at(Vec3::zero(), Vec3::unit_y());
+
+    // add entities to the world
+    commands
+        // plane
+        .spawn(PbrBundle {
+            mesh: meshes.add(Mesh::from(shape::Plane { size: 5.0 })),
+            material: materials.add(Color::rgb(0.3, 0.5, 0.3).into()),
+            ..Default::default()
+        })
+        // cubes
+        .spawn(PbrBundle {
+            mesh: meshes.add(Mesh::from(shape::Cube { size: 1.0 })),
+            material: materials.add(Color::rgb(0.8, 0.7, 0.6).into()),
+            transform: Transform::from_xyz(1.5, 0.5, 1.5),
+            ..Default::default()
+        })
+        .spawn(PbrBundle {
+            mesh: meshes.add(Mesh::from(shape::Cube { size: 1.0 })),
+            material: materials.add(Color::rgb(0.8, 0.7, 0.6).into()),
+            transform: Transform::from_xyz(1.5, 0.5, -1.5),
+            ..Default::default()
+        })
+        .spawn(PbrBundle {
+            mesh: meshes.add(Mesh::from(shape::Cube { size: 1.0 })),
+            material: materials.add(Color::rgb(0.8, 0.7, 0.6).into()),
+            transform: Transform::from_xyz(-1.5, 0.5, 1.5),
+            ..Default::default()
+        })
+        .spawn(PbrBundle {
+            mesh: meshes.add(Mesh::from(shape::Cube { size: 1.0 })),
+            material: materials.add(Color::rgb(0.8, 0.7, 0.6).into()),
+            transform: Transform::from_xyz(-1.5, 0.5, -1.5),
+            ..Default::default()
+        })
+        // light
+        .spawn(LightBundle {
+            transform: Transform::from_xyz(3.0, 8.0, 5.0),
+            ..Default::default()
+        })
+        // camera
+        .spawn(camera);
+}

examples/README.md

@@ -71,6 +71,7 @@ Example | File | Description
 `3d_scene` | [`3d/3d_scene.rs`](./3d/3d_scene.rs) | Simple 3D scene with basic shapes and lighting
 `load_gltf` | [`3d/load_gltf.rs`](./3d/load_gltf.rs) | Loads and renders a gltf file as a scene
 `msaa` | [`3d/msaa.rs`](./3d/msaa.rs) | Configures MSAA (Multi-Sample Anti-Aliasing) for smoother edges
+`orthographic` | [`3d/orthographic.rs`](./3d/orthographic.rs) | Shows how to create a 3D orthographic view (for isometric-look games or CAD applications)
 `parenting` | [`3d/parenting.rs`](./3d/parenting.rs) | Demonstrates parent->child relationships and relative transformations
 `spawner` | [`3d/spawner.rs`](./3d/spawner.rs) | Renders a large number of cubes with changing position and material
 `texture` | [`3d/texture.rs`](./3d/texture.rs) | Shows configuration of texture materials