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b6c003a Apr 8, 2018
@tomaka @yanchith @LPGhatguy
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// Copyright (c) 2016 The vulkano developers
// Licensed under the Apache License, Version 2.0
//> or the MIT
// license <LICENSE-MIT or>,
// at your option. All files in the project carrying such
// notice may not be copied, modified, or distributed except
// according to those terms.
// Welcome to the triangle example!
// This is the only example that is entirely detailed. All the other examples avoid code
// duplication by using helper functions.
// This example assumes that you are already more or less familiar with graphics programming
// and that you want to learn Vulkan. This means that for example it won't go into details about
// what a vertex or a shader is.
// For the purpose of this example all unused code is allowed.
// The `vulkano` crate is the main crate that you must use to use Vulkan.
extern crate vulkano;
// The `vulkano_shader_derive` crate allows us to use the `VulkanoShader` custom derive that we use
// in this example.
extern crate vulkano_shader_derive;
// However the Vulkan library doesn't provide any functionality to create and handle windows, as
// this would be out of scope. In order to open a window, we are going to use the `winit` crate.
extern crate winit;
// The `vulkano_win` crate is the link between `vulkano` and `winit`. Vulkano doesn't know about
// winit, and winit doesn't know about vulkano, so import a crate that will provide a link between
// the two.
extern crate vulkano_win;
use vulkano_win::VkSurfaceBuild;
use vulkano::buffer::BufferUsage;
use vulkano::buffer::CpuAccessibleBuffer;
use vulkano::command_buffer::AutoCommandBufferBuilder;
use vulkano::command_buffer::DynamicState;
use vulkano::device::Device;
use vulkano::framebuffer::Framebuffer;
use vulkano::framebuffer::Subpass;
use vulkano::instance::Instance;
use vulkano::pipeline::GraphicsPipeline;
use vulkano::pipeline::viewport::Viewport;
use vulkano::swapchain;
use vulkano::swapchain::PresentMode;
use vulkano::swapchain::SurfaceTransform;
use vulkano::swapchain::Swapchain;
use vulkano::swapchain::AcquireError;
use vulkano::swapchain::SwapchainCreationError;
use vulkano::sync::now;
use vulkano::sync::GpuFuture;
use std::sync::Arc;
use std::mem;
fn main() {
// The first step of any vulkan program is to create an instance.
let instance = {
// When we create an instance, we have to pass a list of extensions that we want to enable.
// All the window-drawing functionalities are part of non-core extensions that we need
// to enable manually. To do so, we ask the `vulkano_win` crate for the list of extensions
// required to draw to a window.
let extensions = vulkano_win::required_extensions();
// Now creating the instance.
Instance::new(None, &extensions, None).expect("failed to create Vulkan instance")
// We then choose which physical device to use.
// In a real application, there are three things to take into consideration:
// - Some devices may not support some of the optional features that may be required by your
// application. You should filter out the devices that don't support your app.
// - Not all devices can draw to a certain surface. Once you create your window, you have to
// choose a device that is capable of drawing to it.
// - You probably want to leave the choice between the remaining devices to the user.
// For the sake of the example we are just going to use the first device, which should work
// most of the time.
let physical = vulkano::instance::PhysicalDevice::enumerate(&instance)
.next().expect("no device available");
// Some little debug infos.
println!("Using device: {} (type: {:?})",, physical.ty());
// The objective of this example is to draw a triangle on a window. To do so, we first need to
// create a surface that is wrapped in a window.
// This is done by creating a WindowBuilder from the winit crate, then calling the
// build_vk_surface method provided by the VkSurfaceBuild trait from vulkano_win. If you
// ever get an error about build_vk_surface being undefined in one of your projects, this
// probably means that you forgot to import this trait.
// This returns a vulkano::swapchain::Surface object wrapped in a cross-platform vulkano-winit window.
let mut events_loop = winit::EventsLoop::new();
let window = winit::WindowBuilder::new().build_vk_surface(&events_loop, instance.clone()).unwrap();
// Get the dimensions of the viewport. These variables need to be mutable since the viewport
// can change size.
let mut dimensions = {
let (width, height) = window.window().get_inner_size().unwrap();
[width, height]
// The next step is to choose which GPU queue will execute our draw commands.
// Devices can provide multiple queues to run commands in parallel (for example a draw queue
// and a compute queue), similar to CPU threads. This is something you have to have to manage
// manually in Vulkan.
// In a real-life application, we would probably use at least a graphics queue and a transfers
// queue to handle data transfers in parallel. In this example we only use one queue.
// We have to choose which queues to use early on, because we will need this info very soon.
let queue = physical.queue_families().find(|&q| {
// We take the first queue that supports drawing to our window.
q.supports_graphics() && window.is_supported(q).unwrap_or(false)
}).expect("couldn't find a graphical queue family");
// Now initializing the device. This is probably the most important object of Vulkan.
// We have to pass five parameters when creating a device:
// - Which physical device to connect to.
// - A list of optional features and extensions that our program needs to work correctly.
// Some parts of the Vulkan specs are optional and must be enabled manually at device
// creation. In this example the only thing we are going to need is the `khr_swapchain`
// extension that allows us to draw to a window.
// - A list of layers to enable. This is very niche, and you will usually pass `None`.
// - The list of queues that we are going to use. The exact parameter is an iterator whose
// items are `(Queue, f32)` where the floating-point represents the priority of the queue
// between 0.0 and 1.0. The priority of the queue is a hint to the implementation about how
// much it should prioritize queues between one another.
// The list of created queues is returned by the function alongside with the device.
let (device, mut queues) = {
let device_ext = vulkano::device::DeviceExtensions {
khr_swapchain: true,
.. vulkano::device::DeviceExtensions::none()
Device::new(physical, physical.supported_features(), &device_ext,
[(queue, 0.5)].iter().cloned()).expect("failed to create device")
// Since we can request multiple queues, the `queues` variable is in fact an iterator. In this
// example we use only one queue, so we just retreive the first and only element of the
// iterator and throw it away.
let queue =;
// Before we can draw on the surface, we have to create what is called a swapchain. Creating
// a swapchain allocates the color buffers that will contain the image that will ultimately
// be visible on the screen. These images are returned alongside with the swapchain.
let (mut swapchain, mut images) = {
// Querying the capabilities of the surface. When we create the swapchain we can only
// pass values that are allowed by the capabilities.
let caps = window.capabilities(physical)
.expect("failed to get surface capabilities");
// We choose the dimensions of the swapchain to match the current dimensions of the window.
// If `caps.current_extent` is `None`, this means that the window size will be determined
// by the dimensions of the swapchain, in which case we just use the width and height defined above.
//let dimensions = caps.current_extent.unwrap_or([width, height]);
// The alpha mode indicates how the alpha value of the final image will behave. For example
// you can choose whether the window will be opaque or transparent.
let alpha = caps.supported_composite_alpha.iter().next().unwrap();
dimensions = caps.current_extent.unwrap_or(dimensions);
// Choosing the internal format that the images will have.
let format = caps.supported_formats[0].0;
// Please take a look at the docs for the meaning of the parameters we didn't mention.
Swapchain::new(device.clone(), window.clone(), caps.min_image_count, format,
dimensions, 1, caps.supported_usage_flags, &queue,
SurfaceTransform::Identity, alpha, PresentMode::Fifo, true,
None).expect("failed to create swapchain")
// We now create a buffer that will store the shape of our triangle.
let vertex_buffer = {
#[derive(Debug, Clone)]
struct Vertex { position: [f32; 2] }
impl_vertex!(Vertex, position);
CpuAccessibleBuffer::from_iter(device.clone(), BufferUsage::all(), [
Vertex { position: [-0.5, -0.25] },
Vertex { position: [0.0, 0.5] },
Vertex { position: [0.25, -0.1] }
].iter().cloned()).expect("failed to create buffer")
// The next step is to create the shaders.
// The raw shader creation API provided by the vulkano library is unsafe, for various reasons.
// TODO: explain this in details
mod vs {
#[ty = "vertex"]
#[src = "
#version 450
layout(location = 0) in vec2 position;
void main() {
gl_Position = vec4(position, 0.0, 1.0);
struct Dummy;
mod fs {
#[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);
struct Dummy;
let vs = vs::Shader::load(device.clone()).expect("failed to create shader module");
let fs = fs::Shader::load(device.clone()).expect("failed to create shader module");
// At this point, OpenGL initialization would be finished. However in Vulkan it is not. OpenGL
// implicitely does a lot of computation whenever you draw. In Vulkan, you have to do all this
// manually.
// The next step is to create a *render pass*, which is an object that describes where the
// output of the graphics pipeline will go. It describes the layout of the images
// where the colors, depth and/or stencil information will be written.
let render_pass = Arc::new(single_pass_renderpass!(device.clone(),
attachments: {
// `color` is a custom name we give to the first and only attachment.
color: {
// `load: Clear` means that we ask the GPU to clear the content of this
// attachment at the start of the drawing.
load: Clear,
// `store: Store` means that we ask the GPU to store the output of the draw
// in the actual image. We could also ask it to discard the result.
store: Store,
// `format: <ty>` indicates the type of the format of the image. This has to
// be one of the types of the `vulkano::format` module (or alternatively one
// of your structs that implements the `FormatDesc` trait). Here we use the
// generic `vulkano::format::Format` enum because we don't know the format in
// advance.
format: swapchain.format(),
// TODO:
samples: 1,
pass: {
// We use the attachment named `color` as the one and only color attachment.
color: [color],
// No depth-stencil attachment is indicated with empty brackets.
depth_stencil: {}
// Before we draw we have to create what is called a pipeline. This is similar to an OpenGL
// program, but much more specific.
let pipeline = Arc::new(GraphicsPipeline::start()
// We need to indicate the layout of the vertices.
// The type `SingleBufferDefinition` actually contains a template parameter corresponding
// to the type of each vertex. But in this code it is automatically inferred.
// A Vulkan shader can in theory contain multiple entry points, so we have to specify
// which one. The `main` word of `main_entry_point` actually corresponds to the name of
// the entry point.
.vertex_shader(vs.main_entry_point(), ())
// The content of the vertex buffer describes a list of triangles.
// Use a resizable viewport set to draw over the entire window
// See `vertex_shader`.
.fragment_shader(fs.main_entry_point(), ())
// We have to indicate which subpass of which render pass this pipeline is going to be used
// in. The pipeline will only be usable from this particular subpass.
.render_pass(Subpass::from(render_pass.clone(), 0).unwrap())
// Now that our builder is filled, we call `build()` to obtain an actual pipeline.
// The render pass we created above only describes the layout of our framebuffers. Before we
// can draw we also need to create the actual framebuffers.
// Since we need to draw to multiple images, we are going to create a different framebuffer for
// each image.
let mut framebuffers: Option<Vec<Arc<vulkano::framebuffer::Framebuffer<_,_>>>> = None;
// Initialization is finally finished!
// In some situations, the swapchain will become invalid by itself. This includes for example
// when the window is resized (as the images of the swapchain will no longer match the
// window's) or, on Android, when the application went to the background and goes back to the
// foreground.
// In this situation, acquiring a swapchain image or presenting it will return an error.
// Rendering to an image of that swapchain will not produce any error, but may or may not work.
// To continue rendering, we need to recreate the swapchain by creating a new swapchain.
// Here, we remember that we need to do this for the next loop iteration.
let mut recreate_swapchain = false;
// In the loop below we are going to submit commands to the GPU. Submitting a command produces
// an object that implements the `GpuFuture` trait, which holds the resources for as long as
// they are in use by the GPU.
// Destroying the `GpuFuture` blocks until the GPU is finished executing it. In order to avoid
// that, we store the submission of the previous frame here.
let mut previous_frame_end = Box::new(now(device.clone())) as Box<GpuFuture>;
loop {
// It is important to call this function from time to time, otherwise resources will keep
// accumulating and you will eventually reach an out of memory error.
// Calling this function polls various fences in order to determine what the GPU has
// already processed, and frees the resources that are no longer needed.
// If the swapchain needs to be recreated, recreate it
if recreate_swapchain {
// Get the new dimensions for the viewport/framebuffers.
dimensions = {
let (new_width, new_height) = window.window().get_inner_size().unwrap();
[new_width, new_height]
let (new_swapchain, new_images) = match swapchain.recreate_with_dimension(dimensions) {
Ok(r) => r,
// This error tends to happen when the user is manually resizing the window.
// Simply restarting the loop is the easiest way to fix this issue.
Err(SwapchainCreationError::UnsupportedDimensions) => {
Err(err) => panic!("{:?}", err)
mem::replace(&mut swapchain, new_swapchain);
mem::replace(&mut images, new_images);
framebuffers = None;
recreate_swapchain = false;
// Because framebuffers contains an Arc on the old swapchain, we need to
// recreate framebuffers as well.
if framebuffers.is_none() {
let new_framebuffers = Some(images.iter().map(|image| {
mem::replace(&mut framebuffers, new_framebuffers);
// Before we can draw on the output, we have to *acquire* an image from the swapchain. If
// no image is available (which happens if you submit draw commands too quickly), then the
// function will block.
// This operation returns the index of the image that we are allowed to draw upon.
// This function can block if no image is available. The parameter is an optional timeout
// after which the function call will return an error.
let (image_num, acquire_future) = match swapchain::acquire_next_image(swapchain.clone(),
None) {
Ok(r) => r,
Err(AcquireError::OutOfDate) => {
recreate_swapchain = true;
Err(err) => panic!("{:?}", err)
// In order to draw, we have to build a *command buffer*. The command buffer object holds
// the list of commands that are going to be executed.
// Building a command buffer is an expensive operation (usually a few hundred
// microseconds), but it is known to be a hot path in the driver and is expected to be
// optimized.
// Note that we have to pass a queue family when we create the command buffer. The command
// buffer will only be executable on that given queue family.
let command_buffer = AutoCommandBufferBuilder::primary_one_time_submit(device.clone(),
// Before we can draw, we have to *enter a render pass*. There are two methods to do
// this: `draw_inline` and `draw_secondary`. The latter is a bit more advanced and is
// not covered here.
// The third parameter builds the list of values to clear the attachments with. The API
// is similar to the list of attachments when building the framebuffers, except that
// only the attachments that use `load: Clear` appear in the list.
.begin_render_pass(framebuffers.as_ref().unwrap()[image_num].clone(), false,
vec![[0.0, 0.0, 1.0, 1.0].into()])
// We are now inside the first subpass of the render pass. We add a draw command.
// The last two parameters contain the list of resources to pass to the shaders.
// Since we used an `EmptyPipeline` object, the objects have to be `()`.
DynamicState {
line_width: None,
// TODO: Find a way to do this without having to dynamically allocate a Vec every frame.
viewports: Some(vec![Viewport {
origin: [0.0, 0.0],
dimensions: [dimensions[0] as f32, dimensions[1] as f32],
depth_range: 0.0 .. 1.0,
scissors: None,
vertex_buffer.clone(), (), ())
// We leave the render pass by calling `draw_end`. Note that if we had multiple
// subpasses we could have called `next_inline` (or `next_secondary`) to jump to the
// next subpass.
// Finish building the command buffer by calling `build`.
let future = previous_frame_end.join(acquire_future)
.then_execute(queue.clone(), command_buffer).unwrap()
// The color output is now expected to contain our triangle. But in order to show it on
// the screen, we have to *present* the image by calling `present`.
// This function does not actually present the image immediately. Instead it submits a
// present command at the end of the queue. This means that it will only be presented once
// the GPU has finished executing the command buffer that draws the triangle.
.then_swapchain_present(queue.clone(), swapchain.clone(), image_num)
previous_frame_end = Box::new(future) as Box<_>;
// Note that in more complex programs it is likely that one of `acquire_next_image`,
// `command_buffer::submit`, or `present` will block for some time. This happens when the
// GPU's queue is full and the driver has to wait until the GPU finished some work.
// Unfortunately the Vulkan API doesn't provide any way to not wait or to detect when a
// wait would happen. Blocking may be the desired behavior, but if you don't want to
// block you should spawn a separate thread dedicated to submissions.
// Handling the window events in order to close the program when the user wants to close
// it.
let mut done = false;
events_loop.poll_events(|ev| {
match ev {
winit::Event::WindowEvent { event: winit::WindowEvent::Closed, .. } => done = true,
winit::Event::WindowEvent { event: winit::WindowEvent::Resized(_, _), .. } => recreate_swapchain = true,
_ => ()
if done { return; }