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| 1 | +//! This example shows how to make an externally driven headless renderer, |
| 2 | +//! pumping the update loop manually. |
| 3 | +use bevy::{ |
| 4 | + app::SubApps, |
| 5 | + asset::RenderAssetUsages, |
| 6 | + camera::RenderTarget, |
| 7 | + diagnostic::FrameCount, |
| 8 | + image::Image, |
| 9 | + prelude::*, |
| 10 | + render::{ |
| 11 | + render_resource::{Extent3d, PollType, TextureDimension, TextureFormat, TextureUsages}, |
| 12 | + renderer::RenderDevice, |
| 13 | + view::screenshot::{save_to_disk, Screenshot}, |
| 14 | + RenderPlugin, |
| 15 | + }, |
| 16 | + window::ExitCondition, |
| 17 | + winit::WinitPlugin, |
| 18 | +}; |
| 19 | + |
| 20 | +fn main() { |
| 21 | + let mut bw = BevyWrapper::new(); |
| 22 | + |
| 23 | + let target = bw.new_render_target(500, 500); |
| 24 | + bw.spawn_camera(target.clone()); |
| 25 | + for i in 0..10 { |
| 26 | + // Schedule a screenshot for this frame |
| 27 | + bw.screenshot(target.clone(), i); |
| 28 | + // Pump the update loop once |
| 29 | + bw.update(); |
| 30 | + } |
| 31 | + // Loop a couple times more to let screenshot gpu readback and then write to disk |
| 32 | + bw.update(); |
| 33 | + bw.update(); |
| 34 | +} |
| 35 | + |
| 36 | +struct BevyWrapper(SubApps); |
| 37 | + |
| 38 | +impl BevyWrapper { |
| 39 | + fn new() -> Self { |
| 40 | + let render_plugin = RenderPlugin { |
| 41 | + // Make sure all shaders are loaded for the first frame |
| 42 | + synchronous_pipeline_compilation: true, |
| 43 | + ..default() |
| 44 | + }; |
| 45 | + // We don't have any windows, but the WindowPlugin is still needed |
| 46 | + // because a lot of bevy expects it to be there. Just configure it |
| 47 | + // to not have any windows and not exit automatically. |
| 48 | + let window_plugin = WindowPlugin { |
| 49 | + primary_window: None, |
| 50 | + exit_condition: ExitCondition::DontExit, |
| 51 | + ..default() |
| 52 | + }; |
| 53 | + |
| 54 | + let mut app = App::new(); |
| 55 | + app.add_plugins( |
| 56 | + DefaultPlugins |
| 57 | + .set(window_plugin) |
| 58 | + .set(render_plugin) |
| 59 | + // Disable winit because we want to own the update loop ourselves. |
| 60 | + .disable::<WinitPlugin>(), |
| 61 | + ) |
| 62 | + .add_systems(Startup, spawn_test_scene) |
| 63 | + .add_systems(Update, update_camera); |
| 64 | + |
| 65 | + // We yeet the schedule runner and never call app.run(), |
| 66 | + // so we have to finish and clean up ourselves |
| 67 | + app.finish(); |
| 68 | + app.cleanup(); |
| 69 | + |
| 70 | + // We grab the sub apps cus we dont want the runner, as we'll |
| 71 | + // be pumping the update loop ourselves manually. |
| 72 | + Self(std::mem::take(app.sub_apps_mut())) |
| 73 | + } |
| 74 | + |
| 75 | + fn new_render_target(&mut self, width: u32, height: u32) -> RenderTarget { |
| 76 | + let mut target = Image::new_uninit( |
| 77 | + Extent3d { |
| 78 | + width, |
| 79 | + height, |
| 80 | + depth_or_array_layers: 1, |
| 81 | + }, |
| 82 | + TextureDimension::D2, |
| 83 | + TextureFormat::Rgba8UnormSrgb, |
| 84 | + RenderAssetUsages::RENDER_WORLD, |
| 85 | + ); |
| 86 | + // We're going to render to this image, mark it as such |
| 87 | + target.texture_descriptor.usage |= TextureUsages::RENDER_ATTACHMENT; |
| 88 | + self.0 |
| 89 | + .main |
| 90 | + .world_mut() |
| 91 | + .resource_mut::<Assets<Image>>() |
| 92 | + .add(target) |
| 93 | + .into() |
| 94 | + } |
| 95 | + |
| 96 | + fn spawn_camera(&mut self, target: RenderTarget) -> Entity { |
| 97 | + self.0 |
| 98 | + .main |
| 99 | + .world_mut() |
| 100 | + .spawn((Camera3d::default(), target, Transform::IDENTITY)) |
| 101 | + .id() |
| 102 | + } |
| 103 | + |
| 104 | + // Run one world update and wait for rendering to finish. |
| 105 | + fn update(&mut self) { |
| 106 | + self.0.update(); |
| 107 | + // Wait for frame to finish rendering by wait polling the device |
| 108 | + self.0 |
| 109 | + .main |
| 110 | + .world() |
| 111 | + .resource::<RenderDevice>() |
| 112 | + .wgpu_device() |
| 113 | + .poll(PollType::Wait { |
| 114 | + submission_index: None, |
| 115 | + timeout: None, |
| 116 | + }) |
| 117 | + .unwrap(); |
| 118 | + } |
| 119 | + |
| 120 | + // Schedules a screenshot to be captured on the next update. |
| 121 | + fn screenshot(&mut self, target: RenderTarget, i: u32) { |
| 122 | + self.0 |
| 123 | + .main |
| 124 | + .world_mut() |
| 125 | + .spawn(Screenshot::image(target.as_image().unwrap().clone())) |
| 126 | + .observe(save_to_disk(format!("test_images/screenshot{i}.png"))); |
| 127 | + } |
| 128 | +} |
| 129 | + |
| 130 | +fn spawn_test_scene( |
| 131 | + mut commands: Commands, |
| 132 | + mut meshes: ResMut<Assets<Mesh>>, |
| 133 | + mut materials: ResMut<Assets<StandardMaterial>>, |
| 134 | +) { |
| 135 | + commands.spawn(( |
| 136 | + Mesh3d(meshes.add(Circle::new(4.0))), |
| 137 | + MeshMaterial3d(materials.add(Color::WHITE)), |
| 138 | + Transform::from_rotation(Quat::from_rotation_x(-std::f32::consts::FRAC_PI_2)), |
| 139 | + )); |
| 140 | + commands.spawn(( |
| 141 | + Mesh3d(meshes.add(Cuboid::new(2.0, 2.0, 2.0))), |
| 142 | + MeshMaterial3d(materials.add(Color::srgb_u8(124, 144, 255))), |
| 143 | + Transform::from_xyz(0.0, 1.0, 0.0), |
| 144 | + )); |
| 145 | + commands.spawn(( |
| 146 | + PointLight { |
| 147 | + shadow_maps_enabled: true, |
| 148 | + ..default() |
| 149 | + }, |
| 150 | + Transform::from_xyz(4.0, 8.0, 4.0), |
| 151 | + )); |
| 152 | +} |
| 153 | + |
| 154 | +fn update_camera(mut camera: Query<&mut Transform, With<Camera>>, frame_count: Res<FrameCount>) { |
| 155 | + for mut t in camera.iter_mut() { |
| 156 | + let (s, c) = ops::sin_cos(frame_count.0 as f32 * 0.3); |
| 157 | + *t = Transform::from_xyz(s * 10.0, 4.5, c * 10.0).looking_at(Vec3::ZERO, Vec3::Y); |
| 158 | + } |
| 159 | +} |
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