vulkano/examples/src/bin/indirect.rs

// Copyright (c) 2019 The vulkano developers
// Licensed under the Apache License, Version 2.0
// <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT
// license <LICENSE-MIT or http://opensource.org/licenses/MIT>,
// at your option. All files in the project carrying such
// notice may not be copied, modified, or distributed except
// according to those terms.

// Indirect draw example
//
// Indirect draw calls allow us to issue a draw without needing to know the number of vertices
// until later when the draw is executed by the GPU.
//
// This is used in situations where vertices are being generated on the GPU, such as a GPU
// particle simulation, and the exact number of output vertices cannot be known until
// the compute shader has run.
//
// In this example the compute shader is trivial and the number of vertices does not change.
// However is does demonstrate that each compute instance atomically updates the vertex
// counter before filling the vertex buffer.
//
// For an explanation of how the rendering of the triangles takes place see the `triangle.rs`
// example.
//

#[macro_use]
extern crate vulkano;
extern crate vulkano_shaders;
extern crate winit;
extern crate vulkano_win;

use vulkano::buffer::{BufferUsage, CpuBufferPool};
use vulkano::command_buffer::{AutoCommandBufferBuilder, DynamicState, DrawIndirectCommand};
use vulkano::device::{Device, DeviceExtensions};
use vulkano::framebuffer::{Framebuffer, FramebufferAbstract, Subpass, RenderPassAbstract};
use vulkano::image::SwapchainImage;
use vulkano::descriptor::descriptor_set::PersistentDescriptorSet;
use vulkano::instance::{Instance, PhysicalDevice};
use vulkano::pipeline::{ComputePipeline, GraphicsPipeline};
use vulkano::pipeline::viewport::Viewport;
use vulkano::swapchain::{AcquireError, PresentMode, SurfaceTransform, Swapchain, SwapchainCreationError};
use vulkano::swapchain;
use vulkano::sync::{GpuFuture, FlushError};
use vulkano::sync;

use vulkano_win::VkSurfaceBuild;

use winit::event_loop::{EventLoop, ControlFlow};
use winit::window::{Window, WindowBuilder};
use winit::event::{Event, WindowEvent};

use std::sync::Arc;
use std::iter;

// # Vertex Types
// `Vertex` is the vertex type that will be output from the compute shader and be input to the vertex shader.
#[derive(Default, Debug, Clone)]
struct Vertex {
    position: [f32; 2],
}
impl_vertex!(Vertex, position);

fn main() {
    let instance = {
        let extensions = vulkano_win::required_extensions();
        Instance::new(None, &extensions, None).unwrap()
    };

    let physical = PhysicalDevice::enumerate(&instance).next().unwrap();
    println!("Using device: {} (type: {:?})", physical.name(), physical.ty());


    let events_loop = EventLoop::new();
    let surface = WindowBuilder::new().build_vk_surface(&events_loop, instance.clone()).unwrap();
    let window = surface.window();

    let queue_family = physical.queue_families().find(|&q| {
        q.supports_graphics() && surface.is_supported(q).unwrap_or(false)
    }).unwrap();

    let device_ext = DeviceExtensions { khr_swapchain: true, .. DeviceExtensions::none() };
    let (device, mut queues) = Device::new(physical, physical.supported_features(), &device_ext,
        [(queue_family, 0.5)].iter().cloned()).unwrap();

    let queue = queues.next().unwrap();

    let (mut swapchain, images) = {
        let caps = surface.capabilities(physical).unwrap();
        let usage = caps.supported_usage_flags;
        let alpha = caps.supported_composite_alpha.iter().next().unwrap();
        let format = caps.supported_formats[0].0;
        let initial_dimensions = {
            let dimensions: (u32, u32) = window.inner_size().to_physical(window.hidpi_factor()).into();
            [dimensions.0, dimensions.1]
        };

        Swapchain::new(device.clone(), surface.clone(), caps.min_image_count, format,
            initial_dimensions, 1, usage, &queue, SurfaceTransform::Identity, alpha,
            PresentMode::Fifo, true, None).unwrap()
    };

    mod vs {
        vulkano_shaders::shader!{
            ty: "vertex",
            src: "
#version 450

// The triangle vertex positions.
layout(location = 0) in vec2 position;

void main() {
    gl_Position = vec4(position, 0.0, 1.0);
}"
        }
    }

    mod fs {
        vulkano_shaders::shader!{
            ty: "fragment",
            src: "
#version 450

layout(location = 0) out vec4 f_color;

void main() {
    f_color = vec4(1.0, 0.0, 0.0, 1.0);
}
"
        }
    }

    // A simple compute shader that generates vertices. It has two buffers bound: the first is where we output the vertices, the second
    // is the IndirectDrawArgs struct we passed the draw_indirect so we can set the number to vertices to draw
    mod cs {
        vulkano_shaders::shader! {
            ty: "compute",
            src: "
#version 450

layout(local_size_x = 16, local_size_y = 1, local_size_z = 1) in;

layout(set = 0, binding = 0) buffer Output {
    vec2 pos[];
} triangles;

layout(set = 0, binding = 1) buffer IndirectDrawArgs {
    uint vertices;
    uint unused0;
    uint unused1;
    uint unused2;
};

void main() {
    uint idx = gl_GlobalInvocationID.x;

    // each thread of compute shader is going to increment the counter, so we need to use atomic
    // operations for safety. The previous value of the counter is returned so that gives us
    // the offset into the vertex buffer this thread can write it's vertices into.
    uint offset = atomicAdd(vertices, 6);

    vec2 center = vec2(-0.8, -0.8) + idx * vec2(0.1, 0.1);
    triangles.pos[offset + 0] = center + vec2(0.0, 0.0375);
    triangles.pos[offset + 1] = center + vec2(0.025, -0.01725);
    triangles.pos[offset + 2] = center + vec2(-0.025, -0.01725);
    triangles.pos[offset + 3] = center + vec2(0.0, -0.0375);
    triangles.pos[offset + 4] = center + vec2(0.025, 0.01725);
    triangles.pos[offset + 5] = center + vec2(-0.025, 0.01725);
}
"
        }
    }

    let vs = vs::Shader::load(device.clone()).unwrap();
    let fs = fs::Shader::load(device.clone()).unwrap();
    let cs = cs::Shader::load(device.clone()).unwrap();

    // Each frame we generate a new set of vertices and each frame we need a new DrawIndirectCommand struct to
    // set the number of vertices to draw
    let indirect_args_pool: CpuBufferPool<DrawIndirectCommand> = CpuBufferPool::new(device.clone(), BufferUsage::all());
    let vertex_pool : CpuBufferPool<Vertex> = CpuBufferPool::new(device.clone(), BufferUsage::all());

    let compute_pipeline = Arc::new(ComputePipeline::new(device.clone(), &cs.main_entry_point(), &()).unwrap());

    let render_pass = Arc::new(single_pass_renderpass!(
        device.clone(),
        attachments: {
            color: {
                load: Clear,
                store: Store,
                format: swapchain.format(),
                samples: 1,
            }
        },
        pass: {
            color: [color],
            depth_stencil: {}
        }
    ).unwrap());

    let render_pipeline = Arc::new(GraphicsPipeline::start()
        .vertex_input_single_buffer()
        .vertex_shader(vs.main_entry_point(), ())
        .triangle_list()
        .viewports_dynamic_scissors_irrelevant(1)
        .fragment_shader(fs.main_entry_point(), ())
        .render_pass(Subpass::from(render_pass.clone(), 0).unwrap())
        .build(device.clone())
        .unwrap());

    let mut dynamic_state = DynamicState { line_width: None, viewports: None, scissors: None, compare_mask: None, write_mask: None, reference: None };
    let mut framebuffers = window_size_dependent_setup(&images, render_pass.clone(), &mut dynamic_state);
    let mut recreate_swapchain = false;
    let mut previous_frame_end = Some(Box::new(sync::now(device.clone())) as Box<dyn GpuFuture>);

    events_loop.run(move |ev, _, cf| {
        *cf = ControlFlow::Poll;
        let window = surface.window();

        previous_frame_end.as_mut().unwrap().cleanup_finished();

        if recreate_swapchain {
            let dimensions = {
                let dimensions: (u32, u32) = window.inner_size().to_physical(window.hidpi_factor()).into();
                [dimensions.0, dimensions.1]
            };
            let (new_swapchain, new_images) = match swapchain.recreate_with_dimension(dimensions) {
                Ok(r) => r,
                Err(SwapchainCreationError::UnsupportedDimensions) => return,
                Err(err) => panic!("{:?}", err)
            };
            swapchain = new_swapchain;
            framebuffers = window_size_dependent_setup(&new_images, render_pass.clone(), &mut dynamic_state);
            recreate_swapchain = false;
        }

        let (image_num, acquire_future) = match swapchain::acquire_next_image(swapchain.clone(), None) {
            Ok(r) => r,
            Err(AcquireError::OutOfDate) => {
                recreate_swapchain = true;
                return;
            },
            Err(err) => panic!("{:?}", err)
        };

        let clear_values = vec!([0.0, 0.0, 1.0, 1.0].into());

        // Allocate a GPU buffer to hold the arguments for this frames draw call. The compute
        // shader will only update vertex_count, so set the other parameters correctly here.
        let indirect_args = indirect_args_pool.chunk(iter::once(
            DrawIndirectCommand{
                vertex_count: 0,
                instance_count: 1,
                first_vertex: 0,
                first_instance: 0,
            })).unwrap();

        // Allocate a GPU buffer to hold this frames vertices. This needs to be large enough to hold
        // the worst case number of vertices generated by the compute shader
        let vertices = vertex_pool.chunk((0..(6 * 16)).map(|_| Vertex{ position: [0.0;2] })).unwrap();

        // Pass the two buffers to the compute shader
        let cs_desciptor_set = Arc::new(PersistentDescriptorSet::start(compute_pipeline.clone(), 0)
            .add_buffer(vertices.clone()).unwrap()
            .add_buffer(indirect_args.clone()).unwrap()
            .build().unwrap()
        );

        let command_buffer = AutoCommandBufferBuilder::primary_one_time_submit(device.clone(), queue.family()).unwrap()
            // First in the command buffer we dispatch the compute shader to generate the vertices and fill out the draw
            // call arguments
            .dispatch([1,1,1], compute_pipeline.clone(), cs_desciptor_set.clone(), ())
            .unwrap()
            .begin_render_pass(framebuffers[image_num].clone(), false, clear_values)
            .unwrap()
            // The indirect draw call is placed in the command buffer with a reference to the GPU buffer that will
            // contain the arguments when the draw is executed on the GPU
            .draw_indirect(
                render_pipeline.clone(),
                &dynamic_state,
                vertices.clone(),
                indirect_args.clone(),
                (),
                ()
            )
            .unwrap()
            .end_render_pass()
            .unwrap()
            .build().unwrap();

		let prev = previous_frame_end.take();
        let future = prev.unwrap().join(acquire_future)
            .then_execute(queue.clone(), command_buffer).unwrap()
            .then_swapchain_present(queue.clone(), swapchain.clone(), image_num)
            .then_signal_fence_and_flush();

        match future {
            Ok(future) => {
                // This wait is required when using NVIDIA or running on macOS. See https://github.com/vulkano-rs/vulkano/issues/1247
                future.wait(None).unwrap();
                previous_frame_end = Some(Box::new(future) as Box<_>);
            }
            Err(FlushError::OutOfDate) => {
                recreate_swapchain = true;
                previous_frame_end = Some(Box::new(sync::now(device.clone())) as Box<_>);
            }
            Err(e) => {
                println!("{:?}", e);
                previous_frame_end = Some(Box::new(sync::now(device.clone())) as Box<_>);
            }
        }

        match ev {
            Event::WindowEvent { event: WindowEvent::CloseRequested, .. } => *cf = ControlFlow::Exit,
            Event::WindowEvent { event: WindowEvent::Resized(_), .. } => recreate_swapchain = true,
            _ => ()
        }
    });
}

/// This method is called once during initialization, then again whenever the window is resized
fn window_size_dependent_setup(
    images: &[Arc<SwapchainImage<Window>>],
    render_pass: Arc<dyn RenderPassAbstract + Send + Sync>,
    dynamic_state: &mut DynamicState
) -> Vec<Arc<dyn FramebufferAbstract + Send + Sync>> {
    let dimensions = images[0].dimensions();

    let viewport = Viewport {
        origin: [0.0, 0.0],
        dimensions: [dimensions[0] as f32, dimensions[1] as f32],
        depth_range: 0.0 .. 1.0,
    };
    dynamic_state.viewports = Some(vec!(viewport));

    images.iter().map(|image| {
        Arc::new(
            Framebuffer::start(render_pass.clone())
                .add(image.clone()).unwrap()
                .build().unwrap()
        ) as Arc<dyn FramebufferAbstract + Send + Sync>
    }).collect::<Vec<_>>()
}