Projection Improvements (#18458)

# Objective

- Remove a component impl footgun
- Make projection code slightly nicer, and remove the need to import the
projection trait when using the methods on `Projection`.

## Solution

- Do the things.

crates/bevy_pbr/src/light/mod.rs

@@ -7,7 +7,7 @@ use bevy_ecs::{
 use bevy_math::{ops, Mat4, Vec3A, Vec4};
 use bevy_reflect::prelude::*;
 use bevy_render::{
-    camera::{Camera, CameraProjection, Projection},
+    camera::{Camera, Projection},
     extract_component::ExtractComponent,
     extract_resource::ExtractResource,
     mesh::Mesh3d,

crates/bevy_render/src/camera/camera.rs

@@ -5,7 +5,7 @@
 use super::{ClearColorConfig, Projection};
 use crate::{
     batching::gpu_preprocessing::{GpuPreprocessingMode, GpuPreprocessingSupport},
-    camera::{CameraProjection, ManualTextureViewHandle, ManualTextureViews},
+    camera::{ManualTextureViewHandle, ManualTextureViews},
     primitives::Frustum,
     render_asset::RenderAssets,
     render_graph::{InternedRenderSubGraph, RenderSubGraph},
@@ -311,8 +311,8 @@ pub enum ViewportConversionError {
     #[error("computed coordinate beyond `Camera`'s far plane")]
     PastFarPlane,
     /// The Normalized Device Coordinates could not be computed because the `camera_transform`, the
-    /// `world_position`, or the projection matrix defined by [`CameraProjection`] contained `NAN`
-    /// (see [`world_to_ndc`][Camera::world_to_ndc] and [`ndc_to_world`][Camera::ndc_to_world]).
+    /// `world_position`, or the projection matrix defined by [`Projection`] contained `NAN` (see
+    /// [`world_to_ndc`][Camera::world_to_ndc] and [`ndc_to_world`][Camera::ndc_to_world]).
     #[error("found NaN while computing NDC")]
     InvalidData,
 }
@@ -490,7 +490,7 @@ impl Camera {
             .map(|t: &RenderTargetInfo| t.scale_factor)
     }
 
-    /// The projection matrix computed using this camera's [`CameraProjection`].
+    /// The projection matrix computed using this camera's [`Projection`].
     #[inline]
     pub fn clip_from_view(&self) -> Mat4 {
         self.computed.clip_from_view
@@ -655,7 +655,7 @@ impl Camera {
     /// To get the coordinates in the render target's viewport dimensions, you should use
     /// [`world_to_viewport`](Self::world_to_viewport).
     ///
-    /// Returns `None` if the `camera_transform`, the `world_position`, or the projection matrix defined by [`CameraProjection`] contain `NAN`.
+    /// Returns `None` if the `camera_transform`, the `world_position`, or the projection matrix defined by [`Projection`] contain `NAN`.
     ///
     /// # Panics
     ///
@@ -681,7 +681,7 @@ impl Camera {
     /// To get the world space coordinates with the viewport position, you should use
     /// [`world_to_viewport`](Self::world_to_viewport).
     ///
-    /// Returns `None` if the `camera_transform`, the `world_position`, or the projection matrix defined by [`CameraProjection`] contain `NAN`.
+    /// Returns `None` if the `camera_transform`, the `world_position`, or the projection matrix defined by [`Projection`] contain `NAN`.
     ///
     /// # Panics
     ///

crates/bevy_render/src/camera/projection.rs

@@ -1,9 +1,9 @@
 use core::fmt::Debug;
+use core::ops::{Deref, DerefMut};
 
 use crate::{primitives::Frustum, view::VisibilitySystems};
 use bevy_app::{App, Plugin, PostStartup, PostUpdate};
 use bevy_asset::AssetEventSystems;
-use bevy_derive::{Deref, DerefMut};
 use bevy_ecs::prelude::*;
 use bevy_math::{ops, AspectRatio, Mat4, Rect, Vec2, Vec3A, Vec4};
 use bevy_reflect::{std_traits::ReflectDefault, Reflect, ReflectDeserialize, ReflectSerialize};
@@ -131,11 +131,10 @@ mod sealed {
 /// custom projection.
 ///
 /// The contained dynamic object can be downcast into a static type using [`CustomProjection::get`].
-#[derive(Component, Debug, Reflect, Deref, DerefMut)]
+#[derive(Debug, Reflect)]
 #[reflect(Default, Clone)]
 pub struct CustomProjection {
     #[reflect(ignore)]
-    #[deref]
     dyn_projection: Box<dyn sealed::DynCameraProjection>,
 }
 
@@ -204,6 +203,20 @@ impl CustomProjection {
     }
 }
 
+impl Deref for CustomProjection {
+    type Target = dyn CameraProjection;
+
+    fn deref(&self) -> &Self::Target {
+        self.dyn_projection.as_ref()
+    }
+}
+
+impl DerefMut for CustomProjection {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        self.dyn_projection.as_mut()
+    }
+}
+
 /// Component that defines how to compute a [`Camera`]'s projection matrix.
 ///
 /// Common projections, like perspective and orthographic, are provided out of the box to handle the
@@ -240,7 +253,7 @@ impl Projection {
         // that, say, the `Debug` implementation is missing. Wrapping these traits behind a super
         // trait or some other indirection will make the errors harder to understand.
         //
-        // For example, we don't use the `DynCameraProjection`` trait bound, because it is not the
+        // For example, we don't use the `DynCameraProjection` trait bound, because it is not the
         // trait the user should be implementing - they only need to worry about implementing
         // `CameraProjection`.
         P: CameraProjection + Debug + Send + Sync + Clone + 'static,
@@ -251,44 +264,24 @@ impl Projection {
     }
 }
 
-impl CameraProjection for Projection {
-    fn get_clip_from_view(&self) -> Mat4 {
+impl Deref for Projection {
+    type Target = dyn CameraProjection;
+
+    fn deref(&self) -> &Self::Target {
         match self {
-            Projection::Perspective(projection) => projection.get_clip_from_view(),
-            Projection::Orthographic(projection) => projection.get_clip_from_view(),
-            Projection::Custom(projection) => projection.get_clip_from_view(),
+            Projection::Perspective(projection) => projection,
+            Projection::Orthographic(projection) => projection,
+            Projection::Custom(projection) => projection.deref(),
         }
     }
+}
 
-    fn get_clip_from_view_for_sub(&self, sub_view: &super::SubCameraView) -> Mat4 {
+impl DerefMut for Projection {
+    fn deref_mut(&mut self) -> &mut Self::Target {
         match self {
-            Projection::Perspective(projection) => projection.get_clip_from_view_for_sub(sub_view),
-            Projection::Orthographic(projection) => projection.get_clip_from_view_for_sub(sub_view),
-            Projection::Custom(projection) => projection.get_clip_from_view_for_sub(sub_view),
-        }
-    }
-
-    fn update(&mut self, width: f32, height: f32) {
-        match self {
-            Projection::Perspective(projection) => projection.update(width, height),
-            Projection::Orthographic(projection) => projection.update(width, height),
-            Projection::Custom(projection) => projection.update(width, height),
-        }
-    }
-
-    fn far(&self) -> f32 {
-        match self {
-            Projection::Perspective(projection) => projection.far(),
-            Projection::Orthographic(projection) => projection.far(),
-            Projection::Custom(projection) => projection.far(),
-        }
-    }
-
-    fn get_frustum_corners(&self, z_near: f32, z_far: f32) -> [Vec3A; 8] {
-        match self {
-            Projection::Perspective(projection) => projection.get_frustum_corners(z_near, z_far),
-            Projection::Orthographic(projection) => projection.get_frustum_corners(z_near, z_far),
-            Projection::Custom(projection) => projection.get_frustum_corners(z_near, z_far),
+            Projection::Perspective(projection) => projection,
+            Projection::Orthographic(projection) => projection,
+            Projection::Custom(projection) => projection.deref_mut(),
         }
     }
 }

crates/bevy_render/src/view/visibility/mod.rs

@@ -20,7 +20,7 @@ use smallvec::SmallVec;
 
 use super::NoCpuCulling;
 use crate::{
-    camera::{Camera, CameraProjection, Projection},
+    camera::{Camera, Projection},
     mesh::{Mesh, Mesh3d, MeshAabb},
     primitives::{Aabb, Frustum, Sphere},
     sync_world::MainEntity,