Studio Headless Mode (#36)

This PR adds the capaibility to run Stroyteller studio from the command
line, rendering the result to images. This is the basic functionality,
and there are somethings that I am saving for later when we make this a
more fully fledged feature.

Limitations:
- Right now, you cannot do image output resolutions that aren't 2^n.
This is a bug I plan on tackling later.

If you have questions on how the command line works, use the --help
argument.

Let me know what you think!

---------

Co-authored-by: Danny McGee <dannymcgee@gmail.com>

studio/src/scene.rs

@@ -9,19 +9,22 @@ use bevy::{
     math::vec2,
     pbr::ShadowFilteringMethod,
     prelude::*,
-    render::primitives::Aabb,
+    render::{camera::RenderTarget, primitives::Aabb},
     scene::InstanceId,
 };
 
 use space_editor::{prelude::PrefabMarker, space_prefab::component::SceneAutoChild};
 #[cfg(feature = "wasm")]
 use wasm_bindgen::prelude::wasm_bindgen;
+use wgpu::{TextureDescriptor, TextureUsages};
 
 use crate::{
     camera_controller::{CameraController, CameraControllerBundle},
     debug::DebugPoint,
+    is_headless, is_not_headless,
     math::{Combinable, Extrema},
-    MainCamera,
+    screenshot::ScreenCapture,
+    HeadlessSettings, MainCamera,
 };
 
 pub struct ScenePlugin;
@@ -35,7 +38,13 @@ impl Plugin for ScenePlugin {
             .insert_resource(Msaa::Off)
             .add_state::<SceneState>()
             .add_event::<LoadSceneEvent>()
-            .add_systems(Startup, initialize)
+            .add_systems(
+                Startup,
+                (
+                    initialize.run_if(is_not_headless),
+                    initialiaze_headless.run_if(is_headless),
+                ),
+            )
             .add_systems(Update, init_scene_loading.in_set(SceneSpawnerSystem))
             .add_systems(
                 OnEnter(SceneState::Active),
@@ -210,6 +219,55 @@ fn initialize(mut cmd: Commands) {
     ));
 }
 
+fn initialiaze_headless(
+    mut cmd: Commands,
+    mut image_assets: ResMut<Assets<Image>>,
+    headless_settings: Res<HeadlessSettings>,
+) {
+    // Camera, graphics settings
+    let focus = Vec3::ZERO;
+    let camera_xform = Transform::from_xyz(-2.5, 4.5, 5.0).looking_at(focus, Vec3::Y);
+
+    let mut test_image = Image {
+        texture_descriptor: TextureDescriptor {
+            label: Some("render_texture"),
+            size: headless_settings.output_dims,
+            mip_level_count: 1,
+            sample_count: 1,
+            dimension: wgpu::TextureDimension::D2,
+            format: wgpu::TextureFormat::Rgba8UnormSrgb,
+            usage: TextureUsages::TEXTURE_BINDING
+                | TextureUsages::COPY_SRC
+                | TextureUsages::COPY_DST
+                | TextureUsages::RENDER_ATTACHMENT,
+            view_formats: &[],
+        },
+        ..Default::default()
+    };
+
+    test_image.resize(headless_settings.output_dims);
+
+    cmd.spawn((
+        Name::new("Main Camera"),
+        MainCamera,
+        Camera3dBundle {
+            transform: camera_xform,
+            tonemapping: Tonemapping::BlenderFilmic,
+            camera: Camera {
+                hdr: false,
+                target: RenderTarget::Image(image_assets.add(test_image)),
+                ..Default::default()
+            },
+            ..default()
+        },
+        CameraControllerBundle::new(focus, camera_xform.translation),
+        ScreenCapture::number_of_frames(
+            headless_settings.frames_to_capture,
+            &headless_settings.output_dir,
+        ),
+    ));
+}
+
 fn init_scene_loading(mut cmd: Commands, mut er: EventReader<LoadSceneEvent>) {
     if let Some(id) = er.read().last() {
         info!("Loading scene: {}", id.0);