vulkano/examples/occlusion-query/main.rs

// This is a modification of the triangle example, that demonstrates the basics of occlusion
// queries. Occlusion queries allow you to query whether, and sometimes how many, pixels pass the
// depth test in a range of draw calls.

use std::{error::Error, sync::Arc};
use vulkano::{
    buffer::{Buffer, BufferContents, BufferCreateInfo, BufferUsage},
    command_buffer::{
        allocator::StandardCommandBufferAllocator, CommandBufferBeginInfo, CommandBufferLevel,
        CommandBufferUsage, RecordingCommandBuffer, RenderPassBeginInfo,
    },
    device::{
        physical::PhysicalDeviceType, Device, DeviceCreateInfo, DeviceExtensions, QueueCreateInfo,
        QueueFlags,
    },
    format::Format,
    image::{view::ImageView, Image, ImageCreateInfo, ImageType, ImageUsage},
    instance::{Instance, InstanceCreateFlags, InstanceCreateInfo},
    memory::allocator::{AllocationCreateInfo, MemoryTypeFilter, StandardMemoryAllocator},
    pipeline::{
        graphics::{
            color_blend::{ColorBlendAttachmentState, ColorBlendState},
            depth_stencil::{DepthState, DepthStencilState},
            input_assembly::InputAssemblyState,
            multisample::MultisampleState,
            rasterization::RasterizationState,
            vertex_input::{Vertex, VertexDefinition},
            viewport::{Viewport, ViewportState},
            GraphicsPipelineCreateInfo,
        },
        layout::PipelineDescriptorSetLayoutCreateInfo,
        DynamicState, GraphicsPipeline, PipelineLayout, PipelineShaderStageCreateInfo,
    },
    query::{QueryControlFlags, QueryPool, QueryPoolCreateInfo, QueryResultFlags, QueryType},
    render_pass::{Framebuffer, FramebufferCreateInfo, RenderPass, Subpass},
    swapchain::{
        acquire_next_image, Surface, Swapchain, SwapchainCreateInfo, SwapchainPresentInfo,
    },
    sync::{self, GpuFuture},
    Validated, VulkanError, VulkanLibrary,
};
use winit::{
    event::{Event, WindowEvent},
    event_loop::{ControlFlow, EventLoop},
    window::WindowBuilder,
};

fn main() -> Result<(), impl Error> {
    let event_loop = EventLoop::new().unwrap();

    let library = VulkanLibrary::new().unwrap();
    let required_extensions = Surface::required_extensions(&event_loop).unwrap();
    let instance = Instance::new(
        library,
        InstanceCreateInfo {
            flags: InstanceCreateFlags::ENUMERATE_PORTABILITY,
            enabled_extensions: required_extensions,
            ..Default::default()
        },
    )
    .unwrap();

    let window = Arc::new(WindowBuilder::new().build(&event_loop).unwrap());
    let surface = Surface::from_window(instance.clone(), window.clone()).unwrap();

    let device_extensions = DeviceExtensions {
        khr_swapchain: true,
        ..DeviceExtensions::empty()
    };
    let (physical_device, queue_family_index) = instance
        .enumerate_physical_devices()
        .unwrap()
        .filter(|p| p.supported_extensions().contains(&device_extensions))
        .filter_map(|p| {
            p.queue_family_properties()
                .iter()
                .enumerate()
                .position(|(i, q)| {
                    q.queue_flags.intersects(QueueFlags::GRAPHICS)
                        && p.surface_support(i as u32, &surface).unwrap_or(false)
                })
                .map(|i| (p, i as u32))
        })
        .min_by_key(|(p, _)| match p.properties().device_type {
            PhysicalDeviceType::DiscreteGpu => 0,
            PhysicalDeviceType::IntegratedGpu => 1,
            PhysicalDeviceType::VirtualGpu => 2,
            PhysicalDeviceType::Cpu => 3,
            PhysicalDeviceType::Other => 4,
            _ => 5,
        })
        .unwrap();

    println!(
        "Using device: {} (type: {:?})",
        physical_device.properties().device_name,
        physical_device.properties().device_type,
    );

    let (device, mut queues) = Device::new(
        physical_device,
        DeviceCreateInfo {
            enabled_extensions: device_extensions,
            queue_create_infos: vec![QueueCreateInfo {
                queue_family_index,
                ..Default::default()
            }],
            ..Default::default()
        },
    )
    .unwrap();
    let queue = queues.next().unwrap();

    let (mut swapchain, images) = {
        let surface_capabilities = device
            .physical_device()
            .surface_capabilities(&surface, Default::default())
            .unwrap();
        let image_format = device
            .physical_device()
            .surface_formats(&surface, Default::default())
            .unwrap()[0]
            .0;

        Swapchain::new(
            device.clone(),
            surface,
            SwapchainCreateInfo {
                min_image_count: surface_capabilities.min_image_count.max(2),
                image_format,
                image_extent: window.inner_size().into(),
                image_usage: ImageUsage::COLOR_ATTACHMENT,
                composite_alpha: surface_capabilities
                    .supported_composite_alpha
                    .into_iter()
                    .next()
                    .unwrap(),
                ..Default::default()
            },
        )
        .unwrap()
    };

    let memory_allocator = Arc::new(StandardMemoryAllocator::new_default(device.clone()));

    #[derive(BufferContents, Vertex)]
    #[repr(C)]
    struct Vertex {
        #[format(R32G32B32_SFLOAT)]
        position: [f32; 3],
        #[format(R32G32B32_SFLOAT)]
        color: [f32; 3],
    }

    let vertices = [
        // The first triangle (red) is the same one as in the triangle example.
        Vertex {
            position: [-0.5, -0.25, 0.5],
            color: [1.0, 0.0, 0.0],
        },
        Vertex {
            position: [0.0, 0.5, 0.5],
            color: [1.0, 0.0, 0.0],
        },
        Vertex {
            position: [0.25, -0.1, 0.5],
            color: [1.0, 0.0, 0.0],
        },
        // The second triangle (cyan) is the same shape and position as the first, but smaller, and
        // moved behind a bit. It should be completely occluded by the first triangle. (You can
        // lower its z value to put it in front.)
        Vertex {
            position: [-0.25, -0.125, 0.6],
            color: [0.0, 1.0, 1.0],
        },
        Vertex {
            position: [0.0, 0.25, 0.6],
            color: [0.0, 1.0, 1.0],
        },
        Vertex {
            position: [0.125, -0.05, 0.6],
            color: [0.0, 1.0, 1.0],
        },
        // The third triangle (green) is the same shape and size as the first, but moved to the
        // left and behind the second. It is partially occluded by the first two.
        Vertex {
            position: [-0.25, -0.25, 0.7],
            color: [0.0, 1.0, 0.0],
        },
        Vertex {
            position: [0.25, 0.5, 0.7],
            color: [0.0, 1.0, 0.0],
        },
        Vertex {
            position: [0.5, -0.1, 0.7],
            color: [0.0, 1.0, 0.0],
        },
    ];
    let vertex_buffer = Buffer::from_iter(
        memory_allocator.clone(),
        BufferCreateInfo {
            usage: BufferUsage::VERTEX_BUFFER,
            ..Default::default()
        },
        AllocationCreateInfo {
            memory_type_filter: MemoryTypeFilter::PREFER_DEVICE
                | MemoryTypeFilter::HOST_SEQUENTIAL_WRITE,
            ..Default::default()
        },
        vertices,
    )
    .unwrap();

    // Create three buffer slices, one for each triangle.
    let triangle1 = vertex_buffer.clone().slice(0..3);
    let triangle2 = vertex_buffer.clone().slice(3..6);
    let triangle3 = vertex_buffer.slice(6..9);

    // Create a query pool for occlusion queries, with 3 slots.
    let query_pool = QueryPool::new(
        device.clone(),
        QueryPoolCreateInfo {
            query_count: 3,
            ..QueryPoolCreateInfo::query_type(QueryType::Occlusion)
        },
    )
    .unwrap();

    // Create a buffer on the CPU to hold the results of the three queries. Query results are
    // always represented as either `u32` or `u64`. For occlusion queries, you always need one
    // element per query. You can ask for the number of elements needed at runtime by calling
    // `QueryType::result_len`. If you retrieve query results with `with_availability` enabled,
    // then this array needs to be 6 elements long instead of 3.
    let mut query_results = [0u32; 3];

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

                layout(location = 0) in vec3 position;
                layout(location = 1) in vec3 color;

                layout(location = 0) out vec3 v_color;

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

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

                layout(location = 0) in vec3 v_color;
                layout(location = 0) out vec4 f_color;

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

    let render_pass = vulkano::single_pass_renderpass!(
        device.clone(),
        attachments: {
            color: {
                format: swapchain.image_format(),
                samples: 1,
                load_op: Clear,
                store_op: Store,
            },
            depth_stencil: {
                format: Format::D16_UNORM,
                samples: 1,
                load_op: Clear,
                store_op: DontCare,
            },
        },
        pass: {
            color: [color],
            depth_stencil: {depth_stencil},
        },
    )
    .unwrap();

    let pipeline = {
        let vs = vs::load(device.clone())
            .unwrap()
            .entry_point("main")
            .unwrap();
        let fs = fs::load(device.clone())
            .unwrap()
            .entry_point("main")
            .unwrap();
        let vertex_input_state = Vertex::per_vertex().definition(&vs).unwrap();
        let stages = [
            PipelineShaderStageCreateInfo::new(vs),
            PipelineShaderStageCreateInfo::new(fs),
        ];
        let layout = PipelineLayout::new(
            device.clone(),
            PipelineDescriptorSetLayoutCreateInfo::from_stages(&stages)
                .into_pipeline_layout_create_info(device.clone())
                .unwrap(),
        )
        .unwrap();
        let subpass = Subpass::from(render_pass.clone(), 0).unwrap();

        GraphicsPipeline::new(
            device.clone(),
            None,
            GraphicsPipelineCreateInfo {
                stages: stages.into_iter().collect(),
                vertex_input_state: Some(vertex_input_state),
                input_assembly_state: Some(InputAssemblyState::default()),
                viewport_state: Some(ViewportState::default()),
                rasterization_state: Some(RasterizationState::default()),
                multisample_state: Some(MultisampleState::default()),
                // Enable depth testing, which is needed for occlusion queries to make sense at
                // all. If you disable depth testing, every pixel is considered to pass the depth
                // test, so every query will return a nonzero result.
                depth_stencil_state: Some(DepthStencilState {
                    depth: Some(DepthState::simple()),
                    ..Default::default()
                }),
                color_blend_state: Some(ColorBlendState::with_attachment_states(
                    subpass.num_color_attachments(),
                    ColorBlendAttachmentState::default(),
                )),
                dynamic_state: [DynamicState::Viewport].into_iter().collect(),
                subpass: Some(subpass.into()),
                ..GraphicsPipelineCreateInfo::layout(layout)
            },
        )
        .unwrap()
    };

    let mut viewport = Viewport {
        offset: [0.0, 0.0],
        extent: [0.0, 0.0],
        depth_range: 0.0..=1.0,
    };

    let command_buffer_allocator = Arc::new(StandardCommandBufferAllocator::new(
        device.clone(),
        Default::default(),
    ));

    let mut framebuffers = window_size_dependent_setup(
        &images,
        render_pass.clone(),
        &mut viewport,
        memory_allocator.clone(),
    );

    let mut recreate_swapchain = false;
    let mut previous_frame_end = Some(sync::now(device.clone()).boxed());

    event_loop.run(move |event, elwt| {
        elwt.set_control_flow(ControlFlow::Poll);

        match event {
            Event::WindowEvent {
                event: WindowEvent::CloseRequested,
                ..
            } => {
                elwt.exit();
            }
            Event::WindowEvent {
                event: WindowEvent::Resized(_),
                ..
            } => {
                recreate_swapchain = true;
            }
            Event::WindowEvent {
                event: WindowEvent::RedrawRequested,
                ..
            } => {
                let image_extent: [u32; 2] = window.inner_size().into();

                if image_extent.contains(&0) {
                    return;
                }

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

                if recreate_swapchain {
                    let (new_swapchain, new_images) = swapchain
                        .recreate(SwapchainCreateInfo {
                            image_extent,
                            ..swapchain.create_info()
                        })
                        .expect("failed to recreate swapchain");

                    swapchain = new_swapchain;
                    framebuffers = window_size_dependent_setup(
                        &new_images,
                        render_pass.clone(),
                        &mut viewport,
                        memory_allocator.clone(),
                    );
                    recreate_swapchain = false;
                }

                let (image_index, suboptimal, acquire_future) =
                    match acquire_next_image(swapchain.clone(), None).map_err(Validated::unwrap) {
                        Ok(r) => r,
                        Err(VulkanError::OutOfDate) => {
                            recreate_swapchain = true;
                            return;
                        }
                        Err(e) => panic!("failed to acquire next image: {e}"),
                    };

                if suboptimal {
                    recreate_swapchain = true;
                }

                let mut builder = RecordingCommandBuffer::new(
                    command_buffer_allocator.clone(),
                    queue.queue_family_index(),
                    CommandBufferLevel::Primary,
                    CommandBufferBeginInfo {
                        usage: CommandBufferUsage::OneTimeSubmit,
                        ..Default::default()
                    },
                )
                .unwrap();

                // Beginning or resetting a query is unsafe for now.
                unsafe {
                    builder
                        // A query must be reset before each use, including the first use. This
                        // must be done outside a render pass.
                        .reset_query_pool(query_pool.clone(), 0..3)
                        .unwrap()
                        .set_viewport(0, [viewport.clone()].into_iter().collect())
                        .unwrap()
                        .bind_pipeline_graphics(pipeline.clone())
                        .unwrap()
                        .begin_render_pass(
                            RenderPassBeginInfo {
                                clear_values: vec![
                                    Some([0.0, 0.0, 1.0, 1.0].into()),
                                    Some(1.0.into()),
                                ],
                                ..RenderPassBeginInfo::framebuffer(
                                    framebuffers[image_index as usize].clone(),
                                )
                            },
                            Default::default(),
                        )
                        .unwrap()
                        // Begin query 0, then draw the red triangle. Enabling the
                        // `QueryControlFlags::PRECISE` flag would give exact numeric results. This
                        // needs the `occlusion_query_precise` feature to be enabled on the device.
                        .begin_query(
                            query_pool.clone(),
                            0,
                            QueryControlFlags::empty(),
                            // QueryControlFlags::PRECISE,
                        )
                        .unwrap()
                        .bind_vertex_buffers(0, triangle1.clone())
                        .unwrap()
                        .draw(triangle1.len() as u32, 1, 0, 0)
                        .unwrap()
                        // End query 0.
                        .end_query(query_pool.clone(), 0)
                        .unwrap()
                        // Begin query 1 for the cyan triangle.
                        .begin_query(query_pool.clone(), 1, QueryControlFlags::empty())
                        .unwrap()
                        .bind_vertex_buffers(0, triangle2.clone())
                        .unwrap()
                        .draw(triangle2.len() as u32, 1, 0, 0)
                        .unwrap()
                        .end_query(query_pool.clone(), 1)
                        .unwrap()
                        // Finally, query 2 for the green triangle.
                        .begin_query(query_pool.clone(), 2, QueryControlFlags::empty())
                        .unwrap()
                        .bind_vertex_buffers(0, triangle3.clone())
                        .unwrap()
                        .draw(triangle3.len() as u32, 1, 0, 0)
                        .unwrap()
                        .end_query(query_pool.clone(), 2)
                        .unwrap()
                        .end_render_pass(Default::default())
                        .unwrap();
                }

                let command_buffer = builder.end().unwrap();

                let future = previous_frame_end
                    .take()
                    .unwrap()
                    .join(acquire_future)
                    .then_execute(queue.clone(), command_buffer)
                    .unwrap()
                    .then_swapchain_present(
                        queue.clone(),
                        SwapchainPresentInfo::swapchain_image_index(swapchain.clone(), image_index),
                    )
                    .then_signal_fence_and_flush();

                match future.map_err(Validated::unwrap) {
                    Ok(future) => {
                        previous_frame_end = Some(future.boxed());
                    }
                    Err(VulkanError::OutOfDate) => {
                        recreate_swapchain = true;
                        previous_frame_end = Some(sync::now(device.clone()).boxed());
                    }
                    Err(e) => {
                        println!("failed to flush future: {e}");
                        previous_frame_end = Some(sync::now(device.clone()).boxed());
                    }
                }

                // Retrieve the query results. This copies the results to a variable on the CPU.
                // You can also use the `copy_query_pool_results` function on a command buffer to
                // write results to a Vulkano buffer. This could then be used to influence draw
                // operations further down the line, either in the same frame or a future frame.
                #[rustfmt::skip]
                query_pool.get_results(
                    0..3,
                    &mut query_results,
                    // Block the function call until the results are available.
                    // NOTE: If not all the queries have actually been executed, then this will
                    // wait forever for something that never happens!
                    QueryResultFlags::WAIT

                    // Enable this flag to give partial results if available, instead of waiting
                    // for the full results.
                    // | QueryResultFlags::PARTIAL

                    // Blocking and waiting will ensure the results are always available after the
                    // function returns.
                    //
                    // If you disable waiting, then this flag can be enabled to include the
                    // availability of each query's results. You need one extra element per query
                    // in your `query_results` buffer for this. This element will be filled with a
                    // zero/nonzero value indicating availability.
                    // | QueryResultFlags::WITH_AVAILABILITY
                )
                .unwrap();

                // If the `precise` bit was not enabled, then you're only guaranteed to get a
                // boolean result here: zero if all pixels were occluded, nonzero if only some were
                // occluded. Enabling `precise` will give the exact number of pixels.

                // Query 0 (red triangle) will always succeed, because the depth buffer starts
                // empty and will never occlude anything.
                assert_ne!(query_results[0], 0);

                // Query 1 (cyan triangle) will fail, because it's drawn completely behind the
                // first.
                assert_eq!(query_results[1], 0);

                // Query 2 (green triangle) will succeed, because it's only partially occluded.
                assert_ne!(query_results[2], 0);
            }
            Event::AboutToWait => window.request_redraw(),
            _ => (),
        }
    })
}

fn window_size_dependent_setup(
    images: &[Arc<Image>],
    render_pass: Arc<RenderPass>,
    viewport: &mut Viewport,
    memory_allocator: Arc<StandardMemoryAllocator>,
) -> Vec<Arc<Framebuffer>> {
    let extent = images[0].extent();
    viewport.extent = [extent[0] as f32, extent[1] as f32];

    let depth_attachment = ImageView::new_default(
        Image::new(
            memory_allocator,
            ImageCreateInfo {
                image_type: ImageType::Dim2d,
                format: Format::D16_UNORM,
                extent: images[0].extent(),
                usage: ImageUsage::DEPTH_STENCIL_ATTACHMENT | ImageUsage::TRANSIENT_ATTACHMENT,
                ..Default::default()
            },
            AllocationCreateInfo::default(),
        )
        .unwrap(),
    )
    .unwrap();

    images
        .iter()
        .map(|image| {
            let view = ImageView::new_default(image.clone()).unwrap();
            Framebuffer::new(
                render_pass.clone(),
                FramebufferCreateInfo {
                    attachments: vec![view, depth_attachment.clone()],
                    ..Default::default()
                },
            )
            .unwrap()
        })
        .collect::<Vec<_>>()
}