Add "depth_load_op" configuration to 3d Cameras

crates/bevy_core_pipeline/src/core_3d/camera_3d.rs

@@ -1,18 +1,50 @@
 use crate::clear_color::ClearColorConfig;
 use bevy_ecs::{prelude::*, query::QueryItem};
-use bevy_reflect::Reflect;
+use bevy_reflect::{Reflect, ReflectDeserialize};
 use bevy_render::{
     camera::{Camera, CameraRenderGraph, Projection},
     extract_component::ExtractComponent,
     primitives::Frustum,
+    render_resource::LoadOp,
     view::VisibleEntities,
 };
 use bevy_transform::prelude::{GlobalTransform, Transform};
+use serde::{Deserialize, Serialize};
 
-#[derive(Component, Default, Reflect, Clone)]
+/// Configuration for the "main 3d render graph".
+#[derive(Component, Reflect, Clone, Default)]
 #[reflect(Component)]
 pub struct Camera3d {
+    /// The clear color operation to perform for the main 3d pass.
     pub clear_color: ClearColorConfig,
+    /// The depth clear operation to perform for the main 3d pass.
+    pub depth_load_op: Camera3dDepthLoadOp,
+}
+
+/// The depth clear operation to perform for the main 3d pass.
+#[derive(Reflect, Serialize, Deserialize, Clone, Debug)]
+#[reflect_value(Serialize, Deserialize)]
+pub enum Camera3dDepthLoadOp {
+    /// Clear with a specified value.
+    /// Note that 0.0 is the far plane due to bevy's use of reverse-z projections.
+    Clear(f32),
+    /// Load from memory.
+    Load,
+}
+
+impl Default for Camera3dDepthLoadOp {
+    fn default() -> Self {
+        Camera3dDepthLoadOp::Clear(0.0)
+    }
+}
+
+impl From<Camera3dDepthLoadOp> for LoadOp<f32> {
+    fn from(config: Camera3dDepthLoadOp) -> Self {
+        match config {
+            Camera3dDepthLoadOp::Clear(x) => LoadOp::Clear(x),
+            Camera3dDepthLoadOp::Load => LoadOp::Load,
+        }
+    }
 }
 
 impl ExtractComponent for Camera3d {

crates/bevy_core_pipeline/src/core_3d/main_pass_3d_node.rs

@@ -85,8 +85,7 @@ impl Node for MainPass3dNode {
                     view: &depth.view,
                     // NOTE: The opaque main pass loads the depth buffer and possibly overwrites it
                     depth_ops: Some(Operations {
-                        // NOTE: 0.0 is the far plane due to bevy's use of reverse-z projections
-                        load: LoadOp::Clear(0.0),
+                        load: camera_3d.depth_load_op.clone().into(),
                         store: true,
                     }),
                     stencil_ops: None,

examples/3d/render_to_texture.rs

@@ -95,6 +95,7 @@ fn setup(
         .spawn_bundle(Camera3dBundle {
             camera_3d: Camera3d {
                 clear_color: ClearColorConfig::Custom(Color::WHITE),
+                ..default()
             },
             camera: Camera {
                 // render before the "main pass" camera

examples/3d/two_passes.rs

@@ -49,6 +49,7 @@ fn setup(
         transform: Transform::from_xyz(10.0, 10., -5.0).looking_at(Vec3::ZERO, Vec3::Y),
         camera_3d: Camera3d {
             clear_color: ClearColorConfig::None,
+            ..default()
         },
         camera: Camera {
             // renders after / on top of the main camera