vulkano/examples/src/bin/tessellation.rs

// Copyright (c) 2016 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.

// Some relevant documentation:
// *    Tessellation overview           https://www.khronos.org/opengl/wiki/Tessellation
// *    Tessellation Control Shader     https://www.khronos.org/opengl/wiki/Tessellation_Control_Shader
// *    Tessellation Evaluation Shader  https://www.khronos.org/opengl/wiki/Tessellation_Evaluation_Shader
// *    Tessellation real-world usage 1 http://ogldev.atspace.co.uk/www/tutorial30/tutorial30.html
// *    Tessellation real-world usage 2 http://prideout.net/blog/?p=48

// Notable elements of this example:
// *    tessellation control shader and a tessellation evaluation shader
// *    tessellation_shaders(..), patch_list(3) and polygon_mode_line() are called on the pipeline builder

use vulkano::buffer::{BufferUsage, CpuAccessibleBuffer};
use vulkano::command_buffer::{AutoCommandBufferBuilder, DynamicState};
use vulkano::device::{Device, DeviceExtensions};
use vulkano::framebuffer::{Framebuffer, FramebufferAbstract, RenderPassAbstract, Subpass};
use vulkano::image::{ImageUsage, SwapchainImage};
use vulkano::instance::{Instance, PhysicalDevice};
use vulkano::pipeline::viewport::Viewport;
use vulkano::pipeline::GraphicsPipeline;
use vulkano::swapchain;
use vulkano::swapchain::{
    AcquireError, ColorSpace, FullscreenExclusive, PresentMode, SurfaceTransform, Swapchain,
    SwapchainCreationError,
};
use vulkano::sync;
use vulkano::sync::{FlushError, GpuFuture};

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

use std::sync::Arc;

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

            layout(location = 0) in vec2 position;

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

mod tcs {
    vulkano_shaders::shader! {
        ty: "tess_ctrl",
        src: "
            #version 450

            layout (vertices = 3) out; // a value of 3 means a patch consists of a single triangle

            void main(void)
            {
                // save the position of the patch, so the tes can access it
                // We could define our own output variables for this,
                // but gl_out is handily provided.
                gl_out[gl_InvocationID].gl_Position = gl_in[gl_InvocationID].gl_Position;

                gl_TessLevelInner[0] = 10; // many triangles are generated in the center
                gl_TessLevelOuter[0] = 1;  // no triangles are generated for this edge
                gl_TessLevelOuter[1] = 10; // many triangles are generated for this edge
                gl_TessLevelOuter[2] = 10; // many triangles are generated for this edge
                // gl_TessLevelInner[1] = only used when tes uses layout(quads)
                // gl_TessLevelOuter[3] = only used when tes uses layout(quads)
            }
        "
    }
}

// PG
// There is a stage in between tcs and tes called Primitive Generation (PG)
// Shaders cannot be defined for it.
// It takes gl_TessLevelInner and gl_TessLevelOuter and uses them to generate positions within
// the patch and pass them to tes via gl_TessCoord.
//
// When tes uses layout(triangles) then gl_TessCoord is in barrycentric coordinates.
// if layout(quads) is used then gl_TessCoord is in cartesian coordinates.
// Barrycentric coordinates are of the form (x, y, z) where x + y + z = 1
// and the values x, y and z represent the distance from a vertex of the triangle.
// http://mathworld.wolfram.com/BarycentricCoordinates.html

mod tes {
    vulkano_shaders::shader! {
        ty: "tess_eval",
        src: "
            #version 450

            layout(triangles, equal_spacing, cw) in;

            void main(void)
            {
                // retrieve the vertex positions set by the tcs
                vec4 vert_x = gl_in[0].gl_Position;
                vec4 vert_y = gl_in[1].gl_Position;
                vec4 vert_z = gl_in[2].gl_Position;

                // convert gl_TessCoord from barycentric coordinates to cartesian coordinates
                gl_Position = vec4(
                    gl_TessCoord.x * vert_x.x + gl_TessCoord.y * vert_y.x + gl_TessCoord.z * vert_z.x,
                    gl_TessCoord.x * vert_x.y + gl_TessCoord.y * vert_y.y + gl_TessCoord.z * vert_z.y,
                    gl_TessCoord.x * vert_x.z + gl_TessCoord.y * vert_y.z + gl_TessCoord.z * vert_z.z,
                    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, 1.0, 1.0, 1.0);
            }
        "
    }
}

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

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

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

    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 alpha = caps.supported_composite_alpha.iter().next().unwrap();
        let format = caps.supported_formats[0].0;
        let dimensions: [u32; 2] = surface.window().inner_size().into();

        Swapchain::new(
            device.clone(),
            surface.clone(),
            caps.min_image_count,
            format,
            dimensions,
            1,
            ImageUsage::color_attachment(),
            &queue,
            SurfaceTransform::Identity,
            alpha,
            PresentMode::Fifo,
            FullscreenExclusive::Default,
            true,
            ColorSpace::SrgbNonLinear,
        )
        .unwrap()
    };

    let vertex_buffer = {
        #[derive(Default, Debug, Clone)]
        struct Vertex {
            position: [f32; 2],
        }
        vulkano::impl_vertex!(Vertex, position);

        CpuAccessibleBuffer::from_iter(
            device.clone(),
            BufferUsage::all(),
            false,
            [
                Vertex {
                    position: [-0.5, -0.25],
                },
                Vertex {
                    position: [0.0, 0.5],
                },
                Vertex {
                    position: [0.25, -0.1],
                },
                Vertex {
                    position: [0.9, 0.9],
                },
                Vertex {
                    position: [0.9, 0.8],
                },
                Vertex {
                    position: [0.8, 0.8],
                },
                Vertex {
                    position: [-0.9, 0.9],
                },
                Vertex {
                    position: [-0.7, 0.6],
                },
                Vertex {
                    position: [-0.5, 0.9],
                },
            ]
            .iter()
            .cloned(),
        )
        .unwrap()
    };

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

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

    let pipeline = Arc::new(
        GraphicsPipeline::start()
            .vertex_input_single_buffer()
            .vertex_shader(vs.main_entry_point(), ())
            // Actually use the tessellation shaders.
            .tessellation_shaders(tcs.main_entry_point(), (), tes.main_entry_point(), ())
            // use PrimitiveTopology::PathList(3)
            // Use a vertices_per_patch of 3, because we want to convert one triangle into lots of
            // little ones. A value of 4 would convert a rectangle into lots of little triangles.
            .patch_list(3)
            // Enable line mode so we can see the generated vertices.
            .polygon_mode_line()
            .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 recreate_swapchain = false;
    let mut previous_frame_end = Some(sync::now(device.clone()).boxed());
    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);

    event_loop.run(move |event, _, control_flow| match event {
        Event::WindowEvent {
            event: WindowEvent::CloseRequested,
            ..
        } => {
            *control_flow = ControlFlow::Exit;
        }
        Event::WindowEvent {
            event: WindowEvent::Resized(_),
            ..
        } => {
            recreate_swapchain = true;
        }
        Event::RedrawEventsCleared => {
            previous_frame_end.as_mut().unwrap().cleanup_finished();

            if recreate_swapchain {
                let dimensions: [u32; 2] = surface.window().inner_size().into();
                let (new_swapchain, new_images) =
                    match swapchain.recreate_with_dimensions(dimensions) {
                        Ok(r) => r,
                        Err(SwapchainCreationError::UnsupportedDimensions) => return,
                        Err(e) => panic!("Failed to recreate swapchain: {:?}", e),
                    };

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

            let (image_num, suboptimal, acquire_future) =
                match swapchain::acquire_next_image(swapchain.clone(), None) {
                    Ok(r) => r,
                    Err(AcquireError::OutOfDate) => {
                        recreate_swapchain = true;
                        return;
                    }
                    Err(e) => panic!("Failed to acquire next image: {:?}", e),
                };

            if suboptimal {
                recreate_swapchain = true;
            }

            let mut builder =
                AutoCommandBufferBuilder::primary_one_time_submit(device.clone(), queue.family())
                    .unwrap();
            builder
                .begin_render_pass(
                    framebuffers[image_num].clone(),
                    false,
                    vec![[0.0, 0.0, 0.0, 1.0].into()],
                )
                .unwrap()
                .draw(
                    pipeline.clone(),
                    &dynamic_state,
                    vertex_buffer.clone(),
                    (),
                    (),
                )
                .unwrap()
                .end_render_pass()
                .unwrap();
            let command_buffer = builder.build().unwrap();

            let future = previous_frame_end
                .take()
                .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) => {
                    previous_frame_end = Some(future.boxed());
                }
                Err(FlushError::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());
                }
            }
        }
        _ => (),
    });
}

/// 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<_>>()
}