bevy/crates/bevy_render/src/render_graph/base.rs

use super::{
    CameraNode, PassNode, RenderGraph, SharedBuffersNode, TextureCopyNode, WindowSwapChainNode,
    WindowTextureNode,
};
use crate::{
    pass::{
        LoadOp, Operations, PassDescriptor, RenderPassColorAttachment,
        RenderPassDepthStencilAttachment, TextureAttachment,
    },
    texture::{Extent3d, TextureDescriptor, TextureDimension, TextureFormat, TextureUsage},
    Color,
};
use bevy_ecs::{reflect::ReflectComponent, world::World};
use bevy_reflect::Reflect;
use bevy_window::WindowId;

/// A component that indicates that an entity should be drawn in the "main pass"
#[derive(Clone, Debug, Default, Reflect)]
#[reflect(Component)]
pub struct MainPass;

#[derive(Debug)]
pub struct Msaa {
    pub samples: u32,
}

impl Default for Msaa {
    fn default() -> Self {
        Self { samples: 1 }
    }
}

impl Msaa {
    pub fn color_attachment(
        &self,
        attachment: TextureAttachment,
        resolve_target: TextureAttachment,
        ops: Operations<Color>,
    ) -> RenderPassColorAttachment {
        if self.samples > 1 {
            RenderPassColorAttachment {
                attachment,
                resolve_target: Some(resolve_target),
                ops,
            }
        } else {
            RenderPassColorAttachment {
                attachment,
                resolve_target: None,
                ops,
            }
        }
    }
}

#[derive(Debug)]
pub struct BaseRenderGraphConfig {
    pub add_2d_camera: bool,
    pub add_3d_camera: bool,
    pub add_main_depth_texture: bool,
    pub add_main_pass: bool,
    pub connect_main_pass_to_swapchain: bool,
    pub connect_main_pass_to_main_depth_texture: bool,
}

pub mod node {
    pub const PRIMARY_SWAP_CHAIN: &str = "swapchain";
    pub const CAMERA_3D: &str = "camera_3d";
    pub const CAMERA_2D: &str = "camera_2d";
    pub const TEXTURE_COPY: &str = "texture_copy";
    pub const MAIN_DEPTH_TEXTURE: &str = "main_pass_depth_texture";
    pub const MAIN_SAMPLED_COLOR_ATTACHMENT: &str = "main_pass_sampled_color_attachment";
    pub const MAIN_PASS: &str = "main_pass";
    pub const SHARED_BUFFERS: &str = "shared_buffers";
}

pub mod camera {
    pub const CAMERA_3D: &str = "Camera3d";
    pub const CAMERA_2D: &str = "Camera2d";
}

impl Default for BaseRenderGraphConfig {
    fn default() -> Self {
        BaseRenderGraphConfig {
            add_2d_camera: true,
            add_3d_camera: true,
            add_main_pass: true,
            add_main_depth_texture: true,
            connect_main_pass_to_swapchain: true,
            connect_main_pass_to_main_depth_texture: true,
        }
    }
}

/// The "base render graph" provides a core set of render graph nodes which can be used to build any
/// graph. By itself this graph doesn't do much, but it allows Render plugins to interop with each
/// other by having a common set of nodes. It can be customized using `BaseRenderGraphConfig`.
pub(crate) fn add_base_graph(config: &BaseRenderGraphConfig, world: &mut World) {
    let world = world.cell();
    let mut graph = world.get_resource_mut::<RenderGraph>().unwrap();
    let msaa = world.get_resource::<Msaa>().unwrap();

    graph.add_node(node::TEXTURE_COPY, TextureCopyNode::default());
    if config.add_3d_camera {
        graph.add_system_node(node::CAMERA_3D, CameraNode::new(camera::CAMERA_3D));
    }

    if config.add_2d_camera {
        graph.add_system_node(node::CAMERA_2D, CameraNode::new(camera::CAMERA_2D));
    }

    graph.add_node(node::SHARED_BUFFERS, SharedBuffersNode::default());
    if config.add_main_depth_texture {
        graph.add_node(
            node::MAIN_DEPTH_TEXTURE,
            WindowTextureNode::new(
                WindowId::primary(),
                TextureDescriptor {
                    size: Extent3d {
                        depth_or_array_layers: 1,
                        width: 1,
                        height: 1,
                    },
                    mip_level_count: 1,
                    sample_count: msaa.samples,
                    dimension: TextureDimension::D2,
                    format: TextureFormat::Depth32Float, /* PERF: vulkan docs recommend using 24
                                                          * bit depth for better performance */
                    usage: TextureUsage::OUTPUT_ATTACHMENT,
                },
            ),
        );
    }

    if config.add_main_pass {
        let mut main_pass_node = PassNode::<&MainPass>::new(PassDescriptor {
            color_attachments: vec![msaa.color_attachment(
                TextureAttachment::Input("color_attachment".to_string()),
                TextureAttachment::Input("color_resolve_target".to_string()),
                Operations {
                    load: LoadOp::Clear(Color::rgb(0.1, 0.1, 0.1)),
                    store: true,
                },
            )],
            depth_stencil_attachment: Some(RenderPassDepthStencilAttachment {
                attachment: TextureAttachment::Input("depth".to_string()),
                depth_ops: Some(Operations {
                    load: LoadOp::Clear(1.0),
                    store: true,
                }),
                stencil_ops: None,
            }),
            sample_count: msaa.samples,
        });

        main_pass_node.use_default_clear_color(0);

        if config.add_3d_camera {
            main_pass_node.add_camera(camera::CAMERA_3D);
        }

        if config.add_2d_camera {
            main_pass_node.add_camera(camera::CAMERA_2D);
        }

        graph.add_node(node::MAIN_PASS, main_pass_node);

        graph
            .add_node_edge(node::TEXTURE_COPY, node::MAIN_PASS)
            .unwrap();
        graph
            .add_node_edge(node::SHARED_BUFFERS, node::MAIN_PASS)
            .unwrap();

        if config.add_3d_camera {
            graph
                .add_node_edge(node::CAMERA_3D, node::MAIN_PASS)
                .unwrap();
        }

        if config.add_2d_camera {
            graph
                .add_node_edge(node::CAMERA_2D, node::MAIN_PASS)
                .unwrap();
        }
    }

    graph.add_node(
        node::PRIMARY_SWAP_CHAIN,
        WindowSwapChainNode::new(WindowId::primary()),
    );

    if config.connect_main_pass_to_swapchain {
        graph
            .add_slot_edge(
                node::PRIMARY_SWAP_CHAIN,
                WindowSwapChainNode::OUT_TEXTURE,
                node::MAIN_PASS,
                if msaa.samples > 1 {
                    "color_resolve_target"
                } else {
                    "color_attachment"
                },
            )
            .unwrap();
    }

    if msaa.samples > 1 {
        graph.add_node(
            node::MAIN_SAMPLED_COLOR_ATTACHMENT,
            WindowTextureNode::new(
                WindowId::primary(),
                TextureDescriptor {
                    size: Extent3d {
                        depth_or_array_layers: 1,
                        width: 1,
                        height: 1,
                    },
                    mip_level_count: 1,
                    sample_count: msaa.samples,
                    dimension: TextureDimension::D2,
                    format: TextureFormat::default(),
                    usage: TextureUsage::OUTPUT_ATTACHMENT,
                },
            ),
        );

        graph
            .add_slot_edge(
                node::MAIN_SAMPLED_COLOR_ATTACHMENT,
                WindowSwapChainNode::OUT_TEXTURE,
                node::MAIN_PASS,
                "color_attachment",
            )
            .unwrap();
    }

    if config.connect_main_pass_to_main_depth_texture {
        graph
            .add_slot_edge(
                node::MAIN_DEPTH_TEXTURE,
                WindowTextureNode::OUT_TEXTURE,
                node::MAIN_PASS,
                "depth",
            )
            .unwrap();
    }
}