cyborg/src/pass.rs

//! Render pass data structures and interfaces.

use crate::phase::{Phase, PhaseKind};
use std::sync::{Arc, RwLock};

pub mod mesh;

/// Viewport data shared by all passes, once the [ViewportPhase] group is
/// entered.
pub struct ViewportData;

/// Data passed to each render pass's recording phases.
pub struct PhaseData<'a, T> {
    pub phase: Phase,
    pub frame_data: T,
    pub viewport: &'a ViewportData,
}

pub type IndexedPhaseData<'a> = PhaseData<'a, usize>;

/// The render pass interface trait.
///
/// Render passes are persistent structures that share GPU resources, user data,
/// and more across both phases and frames.
///
/// Rendering functions record their GPU commands using the [gpu::RenderBundleEncoder]
/// passed to them.
pub trait RenderPass: Send + Sync {
    /// A structure that contains a pass's per-frame data.
    type FrameData: Send + Sync;

    /// Sets up a new instance of [Self::FrameData].
    ///
    /// Called when a render pass is added to [crate::Renderer].
    fn create_frame_data(&self) -> Self::FrameData;

    /// Initializes this frame's [Self::FrameData], and queries the pass for
    /// which phases to execute.
    ///
    /// This is the only opportunity the render pass has to mutate this frame's
    /// data this frame, so all setup for future phases should be done here.
    fn begin_frame(&self, data: &mut Self::FrameData, phases: &mut Vec<Phase>);

    fn record_commands(&self, data: PhaseData<&Self::FrameData>, cmds: &mut wgpu::CommandEncoder);

    fn record_compute<'a>(
        &'a self,
        data: PhaseData<&Self::FrameData>,
        cmds: &mut wgpu::ComputePass<'a>,
    );

    fn record_render(&self, data: PhaseData<&Self::FrameData>) -> Option<wgpu::RenderBundle>;
}

/// The interface trait for [RenderPassBox], allowing use of a statically-sized
/// [Box] for storage.
///
/// Functions on this trait map one-to-one with [RenderPass], except that
/// frame data is passed by index and not by reference.
pub trait RenderPassBoxTrait: Send + Sync {
    fn begin_frame(&mut self, data_index: usize, phases: &mut Vec<Phase>);

    fn record_commands(&self, data: IndexedPhaseData, cmds: &mut wgpu::CommandEncoder);

    fn record_compute<'a>(&'a self, data: IndexedPhaseData, cmds: &mut wgpu::ComputePass<'a>);

    fn record_render(&self, data: IndexedPhaseData) -> Option<wgpu::RenderBundle>;
}

/// A container for a reference-counted render pass instance and its frame data.
pub struct RenderPassBox<T: RenderPass> {
    render_pass: Arc<T>,
    frame_data: Vec<T::FrameData>,
}

impl<T: 'static + RenderPass> RenderPassBox<T> {
    /// Creates a new boxed render pass.
    ///
    /// Calls to [RenderPassBoxTrait] functions with frame indices greater
    /// than or equal to `frame_num` are out-of-bounds and will panic.
    pub fn new(render_pass: Arc<T>, frame_num: usize) -> Box<dyn RenderPassBoxTrait> {
        let frame_data = {
            (0..frame_num)
                .map(|_| render_pass.create_frame_data())
                .collect()
        };

        Box::new(Self {
            render_pass,
            frame_data,
        })
    }
}

impl<T: RenderPass> RenderPassBox<T> {
    fn get_frame_data<'a>(
        &'a self,
        index: IndexedPhaseData<'a>,
    ) -> PhaseData<'a, &'a T::FrameData> {
        let PhaseData {
            phase,
            frame_data,
            viewport,
        } = index;

        let frame_data = self.frame_data.get(frame_data).unwrap();

        PhaseData {
            phase,
            frame_data,
            viewport,
        }
    }
}

impl<T: RenderPass> RenderPassBoxTrait for RenderPassBox<T> {
    fn begin_frame(&mut self, data_index: usize, phases: &mut Vec<Phase>) {
        let frame_data = &mut self.frame_data[data_index];
        self.render_pass.begin_frame(frame_data, phases)
    }

    fn record_commands(&self, data: IndexedPhaseData, cmds: &mut wgpu::CommandEncoder) {
        let frame_data = self.get_frame_data(data);
        self.render_pass.record_commands(frame_data, cmds)
    }

    fn record_compute<'a>(&'a self, data: IndexedPhaseData, cmds: &mut wgpu::ComputePass<'a>) {
        let frame_data = self.get_frame_data(data);
        self.render_pass.record_compute(frame_data, cmds)
    }

    fn record_render(&self, data: IndexedPhaseData) -> Option<wgpu::RenderBundle> {
        let frame_data = self.get_frame_data(data);
        // let render_pass = self.render_pass.read().unwrap();
        self.render_pass.record_render(frame_data)
    }
}