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Maik Klein 790b2a5b90 Rewrite the loader in the README

2018-11-13 10:07:37 +01:00

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Ash

A very lightweight wrapper around Vulkan

Overview

A true Vulkan API without compromises
Convenience features without limiting functionality
Additional type safety
Device local function pointer loading
No validation, everything is unsafe
Generated from vk.xml
Support for Vulkan 1.1

Features

Explicit returns with `Result`

// function signature
pub fn create_instance(&self,
                       create_info: &vk::InstanceCreateInfo,
                       allocation_callbacks: Option<&vk::AllocationCallbacks>)
                       -> Result<Instance, InstanceError> { .. }
let instance = entry.create_instance(&create_info, None)
    .expect("Instance creation error");

`Vec<T>` instead of mutable slices

pub fn get_swapchain_images_khr(&self,
                                swapchain: vk::SwapchainKHR)
                                -> VkResult<Vec<vk::Image>>;
let present_images = swapchain_loader.get_swapchain_images_khr(swapchain).unwrap();

Note: Functions don't return Vec<T> if this would limit the functionality. See p_next.

Slices

pub fn cmd_pipeline_barrier(&self,
                            command_buffer: vk::CommandBuffer,
                            src_stage_mask: vk::PipelineStageFlags,
                            dst_stage_mask: vk::PipelineStageFlags,
                            dependency_flags: vk::DependencyFlags,
                            memory_barriers: &[vk::MemoryBarrier],
                            buffer_memory_barriers: &[vk::BufferMemoryBarrier],
                            image_memory_barriers: &[vk::ImageMemoryBarrier]);

Default implementation for all types

// No need to manually set the structure type
let desc_alloc_info = vk::DescriptorSetAllocateInfo {
    descriptor_pool: self.pool,
    descriptor_set_count: self.layouts.len() as u32,
    p_set_layouts: self.layouts.as_ptr(),
    ..Default::default()
};

Builder pattern

let pipeline_vertex_input_state_create_info = vk::PipelineVertexInputStateCreateInfo::builder()
    .vertex_binding_descriptions(&Vertex::binding_descriptions())
    .vertex_attribute_descriptions(&Vertex::attribute_descriptions()).build();

Note: No validation is done, the lifetimes only have to live as long as the builder object. It is the responsibility of the user to make sure that the pointers are valid.

Flags and constants as associated constants

// Bitflag
vk::AccessFlags::COLOR_ATTACHMENT_READ | vk::AccessFlags::COLOR_ATTACHMENT_WRITE

// Constant
vk::PipelineBindPoint::GRAPHICS,

Debug/Display for Flags

let flag = vk::AccessFlags::COLOR_ATTACHMENT_READ
        | vk::AccessFlags::COLOR_ATTACHMENT_WRITE;
println!("Debug: {:?}", flag);
println!("Display: {}", flag);
// Prints:
// Debug: AccessFlags(110000000)
// Display: COLOR_ATTACHMENT_READ | COLOR_ATTACHMENT_WRITE

Interop

Vulkan objects inside Ash can be constructed from raw values with Object::from:raw. Useful if you need to interact with a C library.

PipelineBindPoint::from_raw(bindpoint);

Function pointer loading

Ash also takes care of loading the function pointers. Function pointers are split into 3 categories.

Entry: Loads the Vulkan library. Needs to outlive Instance and Device.
Instance: Loads instance level functions. Needs to outlive the Devices it has created.
Device: Loads device local functions.

The loader is just one possible implementation:

Device level functions are retrieved on a per device basis.
Everything is loaded by default, functions that failed to load are initialized to a function that always panics.
Do not call Vulkan 1.1 functions if you have created a 1.0 instance. Doing so will result in a panic.

Custom loaders can be implemented.

Extension loading

Additionally, every Vulkan extension has to be loaded explicitly. You can find all extensions under ash::extensions.

use ash::extensions::Swapchain;
let swapchain_loader = Swapchain::new(&instance, &device);
let swapchain = swapchain_loader.create_swapchain_khr(&swapchain_create_info).unwrap();

Raw function pointers

Raw function pointers are available, if something hasn't been exposed yet in the higher level API. Please open an issue if anything is missing.

device.fp_v1_0().destroy_device(...);

Support for extension names

use ash::extensions::{Swapchain, XlibSurface, Surface, DebugReport};
#[cfg(all(unix, not(target_os = "android")))]
fn extension_names() -> Vec<*const i8> {
    vec![
        Surface::name().as_ptr(),
        XlibSurface::name().as_ptr(),
        DebugReport::name().as_ptr()
    ]
}

Implicit handles

Handles from Instance or Device are passed implicitly.

pub fn create_command_pool(&self,
                           create_info: &vk::CommandPoolCreateInfo)
                           -> VkResult<vk::CommandPool>;

let pool = device.create_command_pool(&pool_create_info).unwrap();

Example

You can find the examples here. All examples currently require: the LunarG Validation layers and a Vulkan library that is visible in your PATH. An easy way to get started is to use the LunarG Vulkan SDK

Windows

Make sure that you have a Vulkan ready driver and install the LunarG Vulkan SDK.

Linux

Make sure that you have a Vulkan ready driver and install the LunarG Vulkan SDK. You also have to add the library and layers to your path. Have a look at my post if you are unsure how to do that.

Triangle

Displays a triangle with vertex colors.

cd examples
cargo run --bin triangle

macOS

Install the LunarG Vulkan SDK. This basically entails extracting the downloaded tarball to any location you choose and then setting a few environment variables. Specifically, if SDK_PATH is set to the root extracted SDK directory,

DYLD_LIBRARY_PATH = $SDK_PATH/macOS/lib
VK_ICD_FILENAMES = $SDK_PATH/macOS/etc/vulkan/icd.d/MoltenVK_icd.json
VK_LAYER_PATH = $SDK_PATH/macOS/etc/vulkan/explicit_layer.d

Texture

Displays a texture on a quad.

cd examples
cargo run --bin texture

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Ash