Merge pull request #50 from SafariMonkey/implement-d3d12

Initial D3D12 implementation + improvements

Cargo.toml

@@ -8,8 +8,10 @@ license = "MIT/Apache-2.0"
 
 
 [features]
-default = []
+default = ["vulkan", "d3d12"]
 force-link = ["openxr/linked"]
+vulkan = ["wgpu-core/vulkan"]
+d3d12 = ["wgpu-core/dx12", "dep:winapi", "dep:d3d12"]
 
 [workspace]
 members = ["examples/android", "examples/demo"]
@@ -21,7 +23,7 @@ bevy = "0.13"
 futures-lite = "2.0.1"
 mint = "0.5.9"
 wgpu = "0.19"
-wgpu-core = { version = "0.19", features = ["vulkan"] }
+wgpu-core = { version = "0.19" }
 wgpu-hal = "0.19"
 eyre = "0.6.11"
 
@@ -31,6 +33,9 @@ openxr = { git = "https://github.com/Ralith/openxrs", rev = "0177d2d", features
 	"static",
 	"mint",
 ] }
+winapi = { version = "0.3.9", optional = true }
+d3d12 = { version = "0.19", features = ["libloading"], optional = true }
+
 [target.'cfg(all(target_family = "unix", not(target_arch = "wasm32")) )'.dependencies]
 openxr = { git = "https://github.com/Ralith/openxrs", rev = "0177d2d", features = [
 	"mint",

src/graphics/d3d12.rs

@@ -0,0 +1,474 @@
+use std::sync::atomic::AtomicBool;
+use std::sync::{Arc, Mutex};
+
+// use anyhow::Context;
+use bevy::math::uvec2;
+use bevy::prelude::*;
+use bevy::render::renderer::{RenderAdapter, RenderAdapterInfo, RenderDevice, RenderQueue};
+use bevy::window::RawHandleWrapper;
+use eyre::{Context, ContextCompat};
+use openxr as xr;
+use wgpu::Instance;
+use wgpu_hal::{api::Dx12, Api};
+use wgpu_hal::{Adapter as HalAdapter, Instance as HalInstance};
+use winapi::shared::dxgiformat::{self, DXGI_FORMAT};
+use winapi::um::{d3d12 as winapi_d3d12, d3dcommon};
+use xr::EnvironmentBlendMode;
+
+use crate::graphics::extensions::XrExtensions;
+use crate::input::XrInput;
+
+use crate::resources::{
+    OXrSessionSetupInfo, Swapchain, SwapchainInner, XrEnvironmentBlendMode, XrFormat, XrFrameState,
+    XrFrameWaiter, XrInstance, XrResolution, XrSession, XrSessionRunning, XrSwapchain, XrViews,
+};
+
+#[cfg(all(feature = "d3d12", windows))]
+use crate::resources::D3D12OXrSessionSetupInfo;
+#[cfg(feature = "vulkan")]
+use crate::resources::VulkanOXrSessionSetupInfo;
+
+use super::{XrAppInfo, XrPreferdBlendMode};
+use crate::VIEW_TYPE;
+
+pub fn initialize_xr_instance(
+    window: Option<RawHandleWrapper>,
+    xr_entry: xr::Entry,
+    reqeusted_extensions: XrExtensions,
+    available_extensions: XrExtensions,
+    prefered_blend_mode: XrPreferdBlendMode,
+    app_info: XrAppInfo,
+) -> eyre::Result<(
+    XrInstance,
+    OXrSessionSetupInfo,
+    XrEnvironmentBlendMode,
+    RenderDevice,
+    RenderQueue,
+    RenderAdapterInfo,
+    RenderAdapter,
+    Instance,
+)> {
+    #[cfg(target_os = "android")]
+    xr_entry.initialize_android_loader()?;
+
+    assert!(available_extensions.raw().khr_d3d12_enable);
+    //info!("available xr exts: {:#?}", available_extensions);
+
+    let mut enabled_extensions: xr::ExtensionSet =
+        (available_extensions & reqeusted_extensions).into();
+    enabled_extensions.khr_d3d12_enable = true;
+
+    let available_layers = xr_entry.enumerate_layers()?;
+    //info!("available xr layers: {:#?}", available_layers);
+
+    let xr_instance = xr_entry.create_instance(
+        &xr::ApplicationInfo {
+            application_name: &app_info.name,
+            engine_name: "Bevy",
+            ..Default::default()
+        },
+        &enabled_extensions,
+        &[],
+    )?;
+    info!("created OpenXR instance");
+    let instance_props = xr_instance.properties()?;
+    let xr_system_id = xr_instance.system(xr::FormFactor::HEAD_MOUNTED_DISPLAY)?;
+    info!("created OpenXR system");
+    let system_props = xr_instance.system_properties(xr_system_id).unwrap();
+    info!(
+        "loaded OpenXR runtime: {} {} {}",
+        instance_props.runtime_name,
+        instance_props.runtime_version,
+        if system_props.system_name.is_empty() {
+            "<unnamed>"
+        } else {
+            &system_props.system_name
+        }
+    );
+
+    let blend_modes = xr_instance.enumerate_environment_blend_modes(xr_system_id, VIEW_TYPE)?;
+    let blend_mode: EnvironmentBlendMode = match prefered_blend_mode {
+        XrPreferdBlendMode::Opaque if blend_modes.contains(&EnvironmentBlendMode::OPAQUE) => {
+            bevy::log::info!("Using Opaque");
+            EnvironmentBlendMode::OPAQUE
+        }
+        XrPreferdBlendMode::Additive if blend_modes.contains(&EnvironmentBlendMode::ADDITIVE) => {
+            bevy::log::info!("Using Additive");
+            EnvironmentBlendMode::ADDITIVE
+        }
+        XrPreferdBlendMode::AlphaBlend
+            if blend_modes.contains(&EnvironmentBlendMode::ALPHA_BLEND) =>
+        {
+            bevy::log::info!("Using AlphaBlend");
+            EnvironmentBlendMode::ALPHA_BLEND
+        }
+        _ => {
+            bevy::log::info!("Using Opaque");
+            EnvironmentBlendMode::OPAQUE
+        }
+    };
+
+    let reqs = xr_instance.graphics_requirements::<xr::D3D12>(xr_system_id)?;
+
+    let instance_descriptor = &wgpu_hal::InstanceDescriptor {
+        name: &app_info.name,
+        dx12_shader_compiler: wgpu::util::dx12_shader_compiler_from_env().unwrap_or(
+            wgpu::Dx12Compiler::Dxc {
+                dxil_path: None,
+                dxc_path: None,
+            },
+        ),
+        flags: wgpu::InstanceFlags::from_build_config().with_env(),
+        gles_minor_version: Default::default(),
+    };
+    let wgpu_raw_instance: wgpu_hal::dx12::Instance =
+        unsafe { wgpu_hal::dx12::Instance::init(instance_descriptor)? };
+    let wgpu_adapters: Vec<wgpu_hal::ExposedAdapter<wgpu_hal::dx12::Api>> =
+        unsafe { wgpu_raw_instance.enumerate_adapters() };
+    let wgpu_exposed_adapter = wgpu_adapters
+        .into_iter()
+        .find(|a| {
+            let mut desc = unsafe { std::mem::zeroed() };
+            unsafe { a.adapter.raw_adapter().GetDesc1(&mut desc) };
+            desc.AdapterLuid.HighPart == reqs.adapter_luid.HighPart
+                && desc.AdapterLuid.LowPart == reqs.adapter_luid.LowPart
+        })
+        .context("failed to find DXGI adapter matching LUID provided by runtime")?;
+
+    let wgpu_instance =
+        unsafe { wgpu::Instance::from_hal::<wgpu_hal::api::Dx12>(wgpu_raw_instance) };
+
+    let wgpu_features = wgpu::Features::TEXTURE_ADAPTER_SPECIFIC_FORMAT_FEATURES
+        | wgpu::Features::MULTIVIEW
+        | wgpu::Features::MULTI_DRAW_INDIRECT_COUNT
+        | wgpu::Features::MULTI_DRAW_INDIRECT;
+
+    let wgpu_limits = wgpu::Limits {
+        max_bind_groups: 8,
+        max_storage_buffer_binding_size: wgpu_exposed_adapter
+            .capabilities
+            .limits
+            .max_storage_buffer_binding_size,
+        max_push_constant_size: 4,
+        ..Default::default()
+    };
+
+    let wgpu_open_device = unsafe {
+        wgpu_exposed_adapter
+            .adapter
+            .open(wgpu_features, &wgpu_limits)?
+    };
+
+    let device_supported_feature_level: d3d12::FeatureLevel =
+        get_device_feature_level(wgpu_open_device.device.raw_device());
+
+    if (device_supported_feature_level as u32) < (reqs.min_feature_level as u32) {
+        panic!(
+            "OpenXR runtime requires D3D12 feature level >= {}",
+            reqs.min_feature_level
+        );
+    }
+
+    let (session, frame_wait, frame_stream) = unsafe {
+        xr_instance.create_session::<xr::D3D12>(
+            xr_system_id,
+            &xr::d3d::SessionCreateInfoD3D12 {
+                device: wgpu_open_device.device.raw_device().as_mut_ptr().cast(),
+                queue: wgpu_open_device.device.raw_queue().as_mut_ptr().cast(),
+            },
+        )
+    }?;
+
+    let wgpu_adapter = unsafe { wgpu_instance.create_adapter_from_hal(wgpu_exposed_adapter) };
+    let raw_device = wgpu_open_device.device.raw_device().as_mut_ptr();
+    let raw_queue = wgpu_open_device.device.raw_queue().as_mut_ptr();
+    let (wgpu_device, wgpu_queue) = unsafe {
+        wgpu_adapter.create_device_from_hal(
+            wgpu_open_device,
+            &wgpu::DeviceDescriptor {
+                label: Some("bevy_oxr device"),
+                required_features: wgpu_features,
+                required_limits: wgpu_limits,
+            },
+            None,
+        )?
+    };
+
+    Ok((
+        xr_instance.into(),
+        OXrSessionSetupInfo::D3D12(D3D12OXrSessionSetupInfo {
+            raw_device,
+            raw_queue,
+            xr_system_id,
+        }),
+        blend_mode.into(),
+        wgpu_device.into(),
+        RenderQueue(wgpu_queue.into()),
+        RenderAdapterInfo(wgpu_adapter.get_info()),
+        RenderAdapter(wgpu_adapter.into()),
+        wgpu_instance.into(),
+    ))
+}
+
+pub fn start_xr_session(
+    window: Option<RawHandleWrapper>,
+    ptrs: &OXrSessionSetupInfo,
+    xr_instance: &XrInstance,
+    render_device: &RenderDevice,
+    render_adapter: &RenderAdapter,
+    wgpu_instance: &Instance,
+) -> eyre::Result<(
+    XrSession,
+    XrResolution,
+    XrFormat,
+    XrSessionRunning,
+    XrFrameWaiter,
+    XrSwapchain,
+    XrInput,
+    XrViews,
+    XrFrameState,
+)> {
+    let wgpu_device = render_device.wgpu_device();
+    let wgpu_adapter = &render_adapter.0;
+
+    #[allow(unreachable_patterns)]
+    let setup_info = match ptrs {
+        OXrSessionSetupInfo::D3D12(v) => v,
+        _ => eyre::bail!("Wrong Graphics Api"),
+    };
+    let (session, frame_wait, frame_stream) = unsafe {
+        xr_instance.create_session::<xr::D3D12>(
+            setup_info.xr_system_id,
+            &xr::d3d::SessionCreateInfoD3D12 {
+                device: setup_info.raw_device.cast(),
+                queue: setup_info.raw_queue.cast(),
+            },
+        )
+    }?;
+
+    let views =
+        xr_instance.enumerate_view_configuration_views(setup_info.xr_system_id, VIEW_TYPE)?;
+    let surface = window.map(|wrapper| unsafe {
+        // SAFETY: Plugins should be set up on the main thread.
+        let handle = wrapper.get_handle();
+        wgpu_instance
+            .create_surface(handle)
+            .expect("Failed to create wgpu surface")
+    });
+    let swapchain_format = surface
+        .as_ref()
+        .map(|surface| surface.get_capabilities(wgpu_adapter).formats[0])
+        .unwrap_or(wgpu::TextureFormat::Rgba8UnormSrgb);
+
+    // TODO: Log swapchain format
+
+    let resolution = uvec2(
+        views[0].recommended_image_rect_width,
+        views[0].recommended_image_rect_height,
+    );
+
+    let handle = session
+        .create_swapchain(&xr::SwapchainCreateInfo {
+            create_flags: xr::SwapchainCreateFlags::EMPTY,
+            usage_flags: xr::SwapchainUsageFlags::COLOR_ATTACHMENT
+                | xr::SwapchainUsageFlags::SAMPLED,
+            format: wgpu_to_d3d12(swapchain_format).expect("Unsupported texture format"),
+            // The Vulkan graphics pipeline we create is not set up for multisampling,
+            // so we hardcode this to 1. If we used a proper multisampling setup, we
+            // could set this to `views[0].recommended_swapchain_sample_count`.
+            sample_count: 1,
+            width: resolution.x,
+            height: resolution.y,
+            face_count: 1,
+            array_size: 2,
+            mip_count: 1,
+        })
+        .unwrap();
+
+    let images = handle.enumerate_images().unwrap();
+
+    let buffers = images
+        .into_iter()
+        .map(|color_image| {
+            info!("image map swapchain");
+            let wgpu_hal_texture = unsafe {
+                <Dx12 as Api>::Device::texture_from_raw(
+                    d3d12::ComPtr::from_raw(color_image as *mut _),
+                    swapchain_format,
+                    wgpu::TextureDimension::D2,
+                    wgpu::Extent3d {
+                        width: resolution.x,
+                        height: resolution.y,
+                        depth_or_array_layers: 2,
+                    },
+                    1,
+                    1,
+                )
+            };
+            let texture = unsafe {
+                wgpu_device.create_texture_from_hal::<Dx12>(
+                    wgpu_hal_texture,
+                    &wgpu::TextureDescriptor {
+                        label: Some("bevy_openxr swapchain"),
+                        size: wgpu::Extent3d {
+                            width: resolution.x,
+                            height: resolution.y,
+                            depth_or_array_layers: 2,
+                        },
+                        mip_level_count: 1,
+                        sample_count: 1,
+                        dimension: wgpu::TextureDimension::D2,
+                        format: swapchain_format,
+                        usage: wgpu::TextureUsages::RENDER_ATTACHMENT
+                            | wgpu::TextureUsages::COPY_DST,
+                        view_formats: &[],
+                    },
+                )
+            };
+            texture
+        })
+        .collect();
+
+    Ok((
+        XrSession::D3D12(session.clone()),
+        resolution.into(),
+        swapchain_format.into(),
+        // TODO: this shouldn't be in here
+        AtomicBool::new(false).into(),
+        frame_wait.into(),
+        Swapchain::D3D12(SwapchainInner {
+            stream: Mutex::new(frame_stream),
+            handle: Mutex::new(handle),
+            buffers,
+            image_index: Mutex::new(0),
+        })
+        .into(),
+        XrInput::new(xr_instance, &session.into_any_graphics())?,
+        Vec::default().into(),
+        // TODO: Feels wrong to return a FrameState here, we probably should just wait for the next frame
+        xr::FrameState {
+            predicted_display_time: xr::Time::from_nanos(1),
+            predicted_display_period: xr::Duration::from_nanos(1),
+            should_render: true,
+        }
+        .into(),
+    ))
+}
+
+// Extracted from https://github.com/gfx-rs/wgpu/blob/1161a22f4fbb4fc204eb06f2ac4243f83e0e980d/wgpu-hal/src/dx12/adapter.rs#L73-L94
+// license: MIT OR Apache-2.0
+fn get_device_feature_level(
+    device: &d3d12::ComPtr<winapi_d3d12::ID3D12Device>,
+) -> d3d12::FeatureLevel {
+    // Detect the highest supported feature level.
+    let d3d_feature_level = [
+        d3d12::FeatureLevel::L12_1,
+        d3d12::FeatureLevel::L12_0,
+        d3d12::FeatureLevel::L11_1,
+        d3d12::FeatureLevel::L11_0,
+    ];
+    type FeatureLevelsInfo = winapi_d3d12::D3D12_FEATURE_DATA_FEATURE_LEVELS;
+    let mut device_levels: FeatureLevelsInfo = unsafe { std::mem::zeroed() };
+    device_levels.NumFeatureLevels = d3d_feature_level.len() as u32;
+    device_levels.pFeatureLevelsRequested = d3d_feature_level.as_ptr().cast();
+    unsafe {
+        device.CheckFeatureSupport(
+            winapi_d3d12::D3D12_FEATURE_FEATURE_LEVELS,
+            (&mut device_levels as *mut FeatureLevelsInfo).cast(),
+            std::mem::size_of::<FeatureLevelsInfo>() as _,
+        )
+    };
+    // This cast should never fail because we only requested feature levels that are already in the enum.
+    let max_feature_level = d3d12::FeatureLevel::try_from(device_levels.MaxSupportedFeatureLevel)
+        .expect("Unexpected feature level");
+    max_feature_level
+}
+
+fn wgpu_to_d3d12(format: wgpu::TextureFormat) -> Option<DXGI_FORMAT> {
+    // Copied wholesale from:
+    // https://github.com/gfx-rs/wgpu/blob/v0.19/wgpu-hal/src/auxil/dxgi/conv.rs#L12-L94
+    // license: MIT OR Apache-2.0
+    use wgpu::TextureFormat as Tf;
+    use winapi::shared::dxgiformat::*;
+
+    Some(match format {
+        Tf::R8Unorm => DXGI_FORMAT_R8_UNORM,
+        Tf::R8Snorm => DXGI_FORMAT_R8_SNORM,
+        Tf::R8Uint => DXGI_FORMAT_R8_UINT,
+        Tf::R8Sint => DXGI_FORMAT_R8_SINT,
+        Tf::R16Uint => DXGI_FORMAT_R16_UINT,
+        Tf::R16Sint => DXGI_FORMAT_R16_SINT,
+        Tf::R16Unorm => DXGI_FORMAT_R16_UNORM,
+        Tf::R16Snorm => DXGI_FORMAT_R16_SNORM,
+        Tf::R16Float => DXGI_FORMAT_R16_FLOAT,
+        Tf::Rg8Unorm => DXGI_FORMAT_R8G8_UNORM,
+        Tf::Rg8Snorm => DXGI_FORMAT_R8G8_SNORM,
+        Tf::Rg8Uint => DXGI_FORMAT_R8G8_UINT,
+        Tf::Rg8Sint => DXGI_FORMAT_R8G8_SINT,
+        Tf::Rg16Unorm => DXGI_FORMAT_R16G16_UNORM,
+        Tf::Rg16Snorm => DXGI_FORMAT_R16G16_SNORM,
+        Tf::R32Uint => DXGI_FORMAT_R32_UINT,
+        Tf::R32Sint => DXGI_FORMAT_R32_SINT,
+        Tf::R32Float => DXGI_FORMAT_R32_FLOAT,
+        Tf::Rg16Uint => DXGI_FORMAT_R16G16_UINT,
+        Tf::Rg16Sint => DXGI_FORMAT_R16G16_SINT,
+        Tf::Rg16Float => DXGI_FORMAT_R16G16_FLOAT,
+        Tf::Rgba8Unorm => DXGI_FORMAT_R8G8B8A8_UNORM,
+        Tf::Rgba8UnormSrgb => DXGI_FORMAT_R8G8B8A8_UNORM_SRGB,
+        Tf::Bgra8UnormSrgb => DXGI_FORMAT_B8G8R8A8_UNORM_SRGB,
+        Tf::Rgba8Snorm => DXGI_FORMAT_R8G8B8A8_SNORM,
+        Tf::Bgra8Unorm => DXGI_FORMAT_B8G8R8A8_UNORM,
+        Tf::Rgba8Uint => DXGI_FORMAT_R8G8B8A8_UINT,
+        Tf::Rgba8Sint => DXGI_FORMAT_R8G8B8A8_SINT,
+        Tf::Rgb9e5Ufloat => DXGI_FORMAT_R9G9B9E5_SHAREDEXP,
+        Tf::Rgb10a2Uint => DXGI_FORMAT_R10G10B10A2_UINT,
+        Tf::Rgb10a2Unorm => DXGI_FORMAT_R10G10B10A2_UNORM,
+        Tf::Rg11b10Float => DXGI_FORMAT_R11G11B10_FLOAT,
+        Tf::Rg32Uint => DXGI_FORMAT_R32G32_UINT,
+        Tf::Rg32Sint => DXGI_FORMAT_R32G32_SINT,
+        Tf::Rg32Float => DXGI_FORMAT_R32G32_FLOAT,
+        Tf::Rgba16Uint => DXGI_FORMAT_R16G16B16A16_UINT,
+        Tf::Rgba16Sint => DXGI_FORMAT_R16G16B16A16_SINT,
+        Tf::Rgba16Unorm => DXGI_FORMAT_R16G16B16A16_UNORM,
+        Tf::Rgba16Snorm => DXGI_FORMAT_R16G16B16A16_SNORM,
+        Tf::Rgba16Float => DXGI_FORMAT_R16G16B16A16_FLOAT,
+        Tf::Rgba32Uint => DXGI_FORMAT_R32G32B32A32_UINT,
+        Tf::Rgba32Sint => DXGI_FORMAT_R32G32B32A32_SINT,
+        Tf::Rgba32Float => DXGI_FORMAT_R32G32B32A32_FLOAT,
+        Tf::Stencil8 => DXGI_FORMAT_D24_UNORM_S8_UINT,
+        Tf::Depth16Unorm => DXGI_FORMAT_D16_UNORM,
+        Tf::Depth24Plus => DXGI_FORMAT_D24_UNORM_S8_UINT,
+        Tf::Depth24PlusStencil8 => DXGI_FORMAT_D24_UNORM_S8_UINT,
+        Tf::Depth32Float => DXGI_FORMAT_D32_FLOAT,
+        Tf::Depth32FloatStencil8 => DXGI_FORMAT_D32_FLOAT_S8X24_UINT,
+        Tf::NV12 => DXGI_FORMAT_NV12,
+        Tf::Bc1RgbaUnorm => DXGI_FORMAT_BC1_UNORM,
+        Tf::Bc1RgbaUnormSrgb => DXGI_FORMAT_BC1_UNORM_SRGB,
+        Tf::Bc2RgbaUnorm => DXGI_FORMAT_BC2_UNORM,
+        Tf::Bc2RgbaUnormSrgb => DXGI_FORMAT_BC2_UNORM_SRGB,
+        Tf::Bc3RgbaUnorm => DXGI_FORMAT_BC3_UNORM,
+        Tf::Bc3RgbaUnormSrgb => DXGI_FORMAT_BC3_UNORM_SRGB,
+        Tf::Bc4RUnorm => DXGI_FORMAT_BC4_UNORM,
+        Tf::Bc4RSnorm => DXGI_FORMAT_BC4_SNORM,
+        Tf::Bc5RgUnorm => DXGI_FORMAT_BC5_UNORM,
+        Tf::Bc5RgSnorm => DXGI_FORMAT_BC5_SNORM,
+        Tf::Bc6hRgbUfloat => DXGI_FORMAT_BC6H_UF16,
+        Tf::Bc6hRgbFloat => DXGI_FORMAT_BC6H_SF16,
+        Tf::Bc7RgbaUnorm => DXGI_FORMAT_BC7_UNORM,
+        Tf::Bc7RgbaUnormSrgb => DXGI_FORMAT_BC7_UNORM_SRGB,
+        Tf::Etc2Rgb8Unorm
+        | Tf::Etc2Rgb8UnormSrgb
+        | Tf::Etc2Rgb8A1Unorm
+        | Tf::Etc2Rgb8A1UnormSrgb
+        | Tf::Etc2Rgba8Unorm
+        | Tf::Etc2Rgba8UnormSrgb
+        | Tf::EacR11Unorm
+        | Tf::EacR11Snorm
+        | Tf::EacRg11Unorm
+        | Tf::EacRg11Snorm
+        | Tf::Astc {
+            block: _,
+            channel: _,
+        } => return None,
+    })
+}

src/graphics/mod.rs

@@ -1,4 +1,8 @@
 pub mod extensions;
+
+#[cfg(all(feature = "d3d12", windows))]
+mod d3d12;
+#[cfg(feature = "vulkan")]
 mod vulkan;
 
 use bevy::ecs::query::With;
@@ -17,6 +21,8 @@ use crate::resources::{
 };
 use crate::OXrSessionSetupInfo;
 
+use crate::Backend;
+
 use openxr as xr;
 
 use self::extensions::XrExtensions;
@@ -63,16 +69,29 @@ pub fn start_xr_session(
     XrViews,
     XrFrameState,
 )> {
-    vulkan::start_xr_session(
+    match session_setup_data {
+        #[cfg(feature = "vulkan")]
+        OXrSessionSetupInfo::Vulkan(_) => vulkan::start_xr_session(
             window,
             session_setup_data,
             xr_instance,
             render_device,
             render_adapter,
             wgpu_instance,
-    )
+        ),
+        #[cfg(all(feature = "d3d12", windows))]
+        OXrSessionSetupInfo::D3D12(_) => d3d12::start_xr_session(
+            window,
+            session_setup_data,
+            xr_instance,
+            render_device,
+            render_adapter,
+            wgpu_instance,
+        ),
+    }
 }
 pub fn initialize_xr_instance(
+    backend_preference: &[Backend],
     window: Option<RawHandleWrapper>,
     reqeusted_extensions: XrExtensions,
     prefered_blend_mode: XrPreferdBlendMode,
@@ -87,11 +106,57 @@ pub fn initialize_xr_instance(
     RenderAdapter,
     Instance,
 )> {
-    vulkan::initialize_xr_instance(window, reqeusted_extensions, prefered_blend_mode, app_info)
+    if backend_preference.is_empty() {
+        eyre::bail!("Cannot initialize with no backend selected");
+    }
+    let xr_entry = xr_entry()?;
+
+    #[cfg(target_os = "android")]
+    xr_entry.initialize_android_loader()?;
+
+    let available_extensions: XrExtensions = xr_entry.enumerate_extensions()?.into();
+
+    for backend in backend_preference {
+        match backend {
+            #[cfg(feature = "vulkan")]
+            Backend::Vulkan => {
+                if !available_extensions.raw().khr_vulkan_enable2 {
+                    continue;
+                }
+                return vulkan::initialize_xr_instance(
+                    window,
+                    xr_entry,
+                    reqeusted_extensions,
+                    available_extensions,
+                    prefered_blend_mode,
+                    app_info,
+                );
+            }
+            #[cfg(all(feature = "d3d12", windows))]
+            Backend::D3D12 => {
+                if !available_extensions.raw().khr_d3d12_enable {
+                    continue;
+                }
+                return d3d12::initialize_xr_instance(
+                    window,
+                    xr_entry,
+                    reqeusted_extensions,
+                    available_extensions,
+                    prefered_blend_mode,
+                    app_info,
+                );
+            }
+        }
+    }
+    eyre::bail!(
+        "No selected backend was supported by the runtime. Selected: {:?}",
+        backend_preference
+    );
 }
 
 pub fn try_full_init(
     world: &mut World,
+    backend_preference: &[Backend],
     reqeusted_extensions: XrExtensions,
     prefered_blend_mode: XrPreferdBlendMode,
     app_info: XrAppInfo,
@@ -115,6 +180,7 @@ pub fn try_full_init(
         render_adapter,
         wgpu_instance,
     ) = initialize_xr_instance(
+        backend_preference,
         primary_window.clone(),
         reqeusted_extensions,
         prefered_blend_mode,

src/graphics/vulkan.rs

@@ -28,7 +28,9 @@ use super::{XrAppInfo, XrPreferdBlendMode};
 
 pub fn initialize_xr_instance(
     window: Option<RawHandleWrapper>,
+    xr_entry: xr::Entry,
     reqeusted_extensions: XrExtensions,
+    available_extensions: XrExtensions,
     prefered_blend_mode: XrPreferdBlendMode,
     app_info: XrAppInfo,
 ) -> eyre::Result<(
@@ -41,14 +43,11 @@ pub fn initialize_xr_instance(
     RenderAdapter,
     Instance,
 )> {
-    let xr_entry = super::xr_entry()?;
-
     #[cfg(target_os = "android")]
     xr_entry.initialize_android_loader()?;
 
-    let available_extensions: XrExtensions = xr_entry.enumerate_extensions()?.into();
     assert!(available_extensions.raw().khr_vulkan_enable2);
-    //info!("available xr exts: {:#?}", available_extensions);
+    // info!("available OpenXR extensions: {:#?}", available_extensions);
 
     let mut enabled_extensions: xr::ExtensionSet =
         (available_extensions & reqeusted_extensions).into();
@@ -59,7 +58,7 @@ pub fn initialize_xr_instance(
     }
 
     let available_layers = xr_entry.enumerate_layers()?;
-    //info!("available xr layers: {:#?}", available_layers);
+    // info!("available OpenXR layers: {:#?}", available_layers);
 
     let xr_instance = xr_entry.create_instance(
         &xr::ApplicationInfo {
@@ -70,10 +69,10 @@ pub fn initialize_xr_instance(
         &enabled_extensions,
         &[],
     )?;
-    info!("created instance");
+    info!("created OpenXR instance");
     let instance_props = xr_instance.properties()?;
     let xr_system_id = xr_instance.system(xr::FormFactor::HEAD_MOUNTED_DISPLAY)?;
-    info!("created system");
+    info!("created OpenXR system");
     let system_props = xr_instance.system_properties(xr_system_id).unwrap();
     info!(
         "loaded OpenXR runtime: {} {} {}",
@@ -123,7 +122,7 @@ pub fn initialize_xr_instance(
         || vk_target_version_xr.major() > reqs.max_api_version_supported.major()
     {
         panic!(
-            "OpenXR runtime requires Vulkan version > {}, < {}.0.0",
+            "OpenXR runtime requires Vulkan version >= {}, < {}.0.0",
             reqs.min_api_version_supported,
             reqs.max_api_version_supported.major() + 1
         );
@@ -139,7 +138,7 @@ pub fn initialize_xr_instance(
         ash::extensions::khr::TimelineSemaphore::name(),
     ];
     info!(
-        "creating vulkan instance with these extensions: {:#?}",
+        "creating Vulkan instance with these extensions: {:#?}",
         extensions
     );
 
@@ -163,7 +162,7 @@ pub fn initialize_xr_instance(
                     .enabled_extension_names(&extensions_cchar) as *const _
                     as *const _,
             )
-            .context("XR error creating Vulkan instance")
+            .context("OpenXR error creating Vulkan instance")
             .unwrap()
             .map_err(vk::Result::from_raw)
             .context("Vulkan error creating Vulkan instance")
@@ -174,7 +173,7 @@ pub fn initialize_xr_instance(
             vk::Instance::from_raw(vk_instance as _),
         )
     };
-    info!("created vulkan instance");
+    info!("created Vulkan instance");
 
     let vk_instance_ptr = vk_instance.handle().as_raw() as *const c_void;
 
@@ -247,7 +246,7 @@ pub fn initialize_xr_instance(
                     vk_physical_device.as_raw() as _,
                     &info as *const _ as *const _,
                 )
-                .context("XR error creating Vulkan device")?
+                .context("OpenXR error creating Vulkan device")?
                 .map_err(vk::Result::from_raw)
                 .context("Vulkan error creating Vulkan device")?;
 
@@ -401,7 +400,7 @@ pub fn start_xr_session(
                 <V as Api>::Device::texture_from_raw(
                     color_image,
                     &wgpu_hal::TextureDescriptor {
-                        label: Some("VR Swapchain"),
+                        label: Some("bevy_openxr swapchain"), // unused internally
                         size: wgpu::Extent3d {
                             width: resolution.x,
                             height: resolution.y,
@@ -423,7 +422,7 @@ pub fn start_xr_session(
                 wgpu_device.create_texture_from_hal::<V>(
                     wgpu_hal_texture,
                     &wgpu::TextureDescriptor {
-                        label: Some("VR Swapchain"),
+                        label: Some("bevy_openxr swapchain"),
                         size: wgpu::Extent3d {
                             width: resolution.x,
                             height: resolution.y,
@@ -470,67 +469,136 @@ pub fn start_xr_session(
 }
 
 fn wgpu_to_vulkan(format: wgpu::TextureFormat) -> vk::Format {
-    use vk::Format;
+    // Copied with minor modification from:
+    // https://github.com/gfx-rs/wgpu/blob/v0.19/wgpu-hal/src/vulkan/conv.rs#L5C1-L153
+    // license: MIT OR Apache-2.0
+    use ash::vk::Format as F;
+    use wgpu::TextureFormat as Tf;
+    use wgpu::{AstcBlock, AstcChannel};
     match format {
-        wgpu::TextureFormat::R8Unorm => Format::R8_UNORM,
+        Tf::R8Unorm => F::R8_UNORM,
-        wgpu::TextureFormat::R8Snorm => Format::R8_SNORM,
+        Tf::R8Snorm => F::R8_SNORM,
-        wgpu::TextureFormat::R8Uint => Format::R8_UINT,
+        Tf::R8Uint => F::R8_UINT,
-        wgpu::TextureFormat::R8Sint => Format::R8_SINT,
+        Tf::R8Sint => F::R8_SINT,
-        wgpu::TextureFormat::R16Uint => Format::R16_UINT,
+        Tf::R16Uint => F::R16_UINT,
-        wgpu::TextureFormat::R16Sint => Format::R16_SINT,
+        Tf::R16Sint => F::R16_SINT,
-        wgpu::TextureFormat::R16Unorm => Format::R16_UNORM,
+        Tf::R16Unorm => F::R16_UNORM,
-        wgpu::TextureFormat::R16Snorm => Format::R16_SNORM,
+        Tf::R16Snorm => F::R16_SNORM,
-        wgpu::TextureFormat::R16Float => Format::R16_SFLOAT,
+        Tf::R16Float => F::R16_SFLOAT,
-        wgpu::TextureFormat::Rg8Unorm => Format::R8G8_UNORM,
+        Tf::Rg8Unorm => F::R8G8_UNORM,
-        wgpu::TextureFormat::Rg8Snorm => Format::R8G8_SNORM,
+        Tf::Rg8Snorm => F::R8G8_SNORM,
-        wgpu::TextureFormat::Rg8Uint => Format::R8G8_UINT,
+        Tf::Rg8Uint => F::R8G8_UINT,
-        wgpu::TextureFormat::Rg8Sint => Format::R8G8_SINT,
+        Tf::Rg8Sint => F::R8G8_SINT,
-        wgpu::TextureFormat::R32Uint => Format::R32_UINT,
+        Tf::Rg16Unorm => F::R16G16_UNORM,
-        wgpu::TextureFormat::R32Sint => Format::R32_SINT,
+        Tf::Rg16Snorm => F::R16G16_SNORM,
-        wgpu::TextureFormat::R32Float => Format::R32_SFLOAT,
+        Tf::R32Uint => F::R32_UINT,
-        wgpu::TextureFormat::Rg16Uint => Format::R16G16_UINT,
+        Tf::R32Sint => F::R32_SINT,
-        wgpu::TextureFormat::Rg16Sint => Format::R16G16_SINT,
+        Tf::R32Float => F::R32_SFLOAT,
-        wgpu::TextureFormat::Rg16Unorm => Format::R16G16_UNORM,
+        Tf::Rg16Uint => F::R16G16_UINT,
-        wgpu::TextureFormat::Rg16Snorm => Format::R16G16_SNORM,
+        Tf::Rg16Sint => F::R16G16_SINT,
-        wgpu::TextureFormat::Rg16Float => Format::R16G16_SFLOAT,
+        Tf::Rg16Float => F::R16G16_SFLOAT,
-        wgpu::TextureFormat::Rgba8Unorm => Format::R8G8B8A8_UNORM,
+        Tf::Rgba8Unorm => F::R8G8B8A8_UNORM,
-        wgpu::TextureFormat::Rgba8UnormSrgb => Format::R8G8B8A8_SRGB,
+        Tf::Rgba8UnormSrgb => F::R8G8B8A8_SRGB,
-        wgpu::TextureFormat::Rgba8Snorm => Format::R8G8B8A8_SNORM,
+        Tf::Bgra8UnormSrgb => F::B8G8R8A8_SRGB,
-        wgpu::TextureFormat::Rgba8Uint => Format::R8G8B8A8_UINT,
+        Tf::Rgba8Snorm => F::R8G8B8A8_SNORM,
-        wgpu::TextureFormat::Rgba8Sint => Format::R8G8B8A8_SINT,
+        Tf::Bgra8Unorm => F::B8G8R8A8_UNORM,
-        wgpu::TextureFormat::Bgra8Unorm => Format::B8G8R8A8_UNORM,
+        Tf::Rgba8Uint => F::R8G8B8A8_UINT,
-        wgpu::TextureFormat::Bgra8UnormSrgb => Format::B8G8R8A8_SRGB,
+        Tf::Rgba8Sint => F::R8G8B8A8_SINT,
-        wgpu::TextureFormat::Rgb9e5Ufloat => Format::E5B9G9R9_UFLOAT_PACK32, // this might be the wrong type??? i can't tell
+        Tf::Rgb10a2Uint => F::A2B10G10R10_UINT_PACK32,
-        wgpu::TextureFormat::Rgb10a2Unorm => Format::A2R10G10B10_UNORM_PACK32,
+        Tf::Rgb10a2Unorm => F::A2B10G10R10_UNORM_PACK32,
-        wgpu::TextureFormat::Rg11b10Float => panic!("this texture type invokes nothing but fear within my soul and i don't think vulkan has a proper type for this"),
+        Tf::Rg11b10Float => F::B10G11R11_UFLOAT_PACK32,
-        wgpu::TextureFormat::Rg32Uint => Format::R32G32_UINT,
+        Tf::Rg32Uint => F::R32G32_UINT,
-        wgpu::TextureFormat::Rg32Sint => Format::R32G32_SINT,
+        Tf::Rg32Sint => F::R32G32_SINT,
-        wgpu::TextureFormat::Rg32Float => Format::R32G32_SFLOAT,
+        Tf::Rg32Float => F::R32G32_SFLOAT,
-        wgpu::TextureFormat::Rgba16Uint => Format::R16G16B16A16_UINT,
+        Tf::Rgba16Uint => F::R16G16B16A16_UINT,
-        wgpu::TextureFormat::Rgba16Sint => Format::R16G16B16A16_SINT,
+        Tf::Rgba16Sint => F::R16G16B16A16_SINT,
-        wgpu::TextureFormat::Rgba16Unorm => Format::R16G16B16A16_UNORM,
+        Tf::Rgba16Unorm => F::R16G16B16A16_UNORM,
-        wgpu::TextureFormat::Rgba16Snorm => Format::R16G16B16A16_SNORM,
+        Tf::Rgba16Snorm => F::R16G16B16A16_SNORM,
-        wgpu::TextureFormat::Rgba16Float => Format::R16G16B16A16_SFLOAT,
+        Tf::Rgba16Float => F::R16G16B16A16_SFLOAT,
-        wgpu::TextureFormat::Rgba32Uint => Format::R32G32B32A32_UINT,
+        Tf::Rgba32Uint => F::R32G32B32A32_UINT,
-        wgpu::TextureFormat::Rgba32Sint => Format::R32G32B32A32_SINT,
+        Tf::Rgba32Sint => F::R32G32B32A32_SINT,
-        wgpu::TextureFormat::Rgba32Float => Format::R32G32B32A32_SFLOAT,
+        Tf::Rgba32Float => F::R32G32B32A32_SFLOAT,
-        wgpu::TextureFormat::Stencil8 => Format::S8_UINT,
+        Tf::Depth32Float => F::D32_SFLOAT,
-        wgpu::TextureFormat::Depth16Unorm => Format::D16_UNORM,
+        Tf::Depth32FloatStencil8 => F::D32_SFLOAT_S8_UINT,
-        wgpu::TextureFormat::Depth24Plus => Format::X8_D24_UNORM_PACK32,
+        Tf::Depth24Plus | Tf::Depth24PlusStencil8 | Tf::Stencil8 => {
-        wgpu::TextureFormat::Depth24PlusStencil8 => Format::D24_UNORM_S8_UINT,
+            panic!("Cannot convert format that is dependent on device properties")
-        wgpu::TextureFormat::Depth32Float => Format::D32_SFLOAT,
+        }
-        wgpu::TextureFormat::Depth32FloatStencil8 => Format::D32_SFLOAT_S8_UINT,
+        Tf::Depth16Unorm => F::D16_UNORM,
-        wgpu::TextureFormat::Etc2Rgb8Unorm => Format::ETC2_R8G8B8_UNORM_BLOCK,
+        Tf::NV12 => F::G8_B8R8_2PLANE_420_UNORM,
-        wgpu::TextureFormat::Etc2Rgb8UnormSrgb => Format::ETC2_R8G8B8_SRGB_BLOCK,
+        Tf::Rgb9e5Ufloat => F::E5B9G9R9_UFLOAT_PACK32,
-        wgpu::TextureFormat::Etc2Rgb8A1Unorm => Format::ETC2_R8G8B8A1_UNORM_BLOCK,
+        Tf::Bc1RgbaUnorm => F::BC1_RGBA_UNORM_BLOCK,
-        wgpu::TextureFormat::Etc2Rgb8A1UnormSrgb => Format::ETC2_R8G8B8A1_SRGB_BLOCK,
+        Tf::Bc1RgbaUnormSrgb => F::BC1_RGBA_SRGB_BLOCK,
-        wgpu::TextureFormat::Etc2Rgba8Unorm => Format::ETC2_R8G8B8A8_UNORM_BLOCK,
+        Tf::Bc2RgbaUnorm => F::BC2_UNORM_BLOCK,
-        wgpu::TextureFormat::Etc2Rgba8UnormSrgb => Format::ETC2_R8G8B8A8_SRGB_BLOCK,
+        Tf::Bc2RgbaUnormSrgb => F::BC2_SRGB_BLOCK,
-        wgpu::TextureFormat::EacR11Unorm => Format::EAC_R11_UNORM_BLOCK,
+        Tf::Bc3RgbaUnorm => F::BC3_UNORM_BLOCK,
-        wgpu::TextureFormat::EacR11Snorm => Format::EAC_R11_SNORM_BLOCK,
+        Tf::Bc3RgbaUnormSrgb => F::BC3_SRGB_BLOCK,
-        wgpu::TextureFormat::EacRg11Unorm => Format::EAC_R11G11_UNORM_BLOCK,
+        Tf::Bc4RUnorm => F::BC4_UNORM_BLOCK,
-        wgpu::TextureFormat::EacRg11Snorm => Format::EAC_R11G11_SNORM_BLOCK,
+        Tf::Bc4RSnorm => F::BC4_SNORM_BLOCK,
-        wgpu::TextureFormat::Astc { .. } => panic!("please god kill me now"),
+        Tf::Bc5RgUnorm => F::BC5_UNORM_BLOCK,
-        _ => panic!("fuck no")
+        Tf::Bc5RgSnorm => F::BC5_SNORM_BLOCK,
+        Tf::Bc6hRgbUfloat => F::BC6H_UFLOAT_BLOCK,
+        Tf::Bc6hRgbFloat => F::BC6H_SFLOAT_BLOCK,
+        Tf::Bc7RgbaUnorm => F::BC7_UNORM_BLOCK,
+        Tf::Bc7RgbaUnormSrgb => F::BC7_SRGB_BLOCK,
+        Tf::Etc2Rgb8Unorm => F::ETC2_R8G8B8_UNORM_BLOCK,
+        Tf::Etc2Rgb8UnormSrgb => F::ETC2_R8G8B8_SRGB_BLOCK,
+        Tf::Etc2Rgb8A1Unorm => F::ETC2_R8G8B8A1_UNORM_BLOCK,
+        Tf::Etc2Rgb8A1UnormSrgb => F::ETC2_R8G8B8A1_SRGB_BLOCK,
+        Tf::Etc2Rgba8Unorm => F::ETC2_R8G8B8A8_UNORM_BLOCK,
+        Tf::Etc2Rgba8UnormSrgb => F::ETC2_R8G8B8A8_SRGB_BLOCK,
+        Tf::EacR11Unorm => F::EAC_R11_UNORM_BLOCK,
+        Tf::EacR11Snorm => F::EAC_R11_SNORM_BLOCK,
+        Tf::EacRg11Unorm => F::EAC_R11G11_UNORM_BLOCK,
+        Tf::EacRg11Snorm => F::EAC_R11G11_SNORM_BLOCK,
+        Tf::Astc { block, channel } => match channel {
+            AstcChannel::Unorm => match block {
+                AstcBlock::B4x4 => F::ASTC_4X4_UNORM_BLOCK,
+                AstcBlock::B5x4 => F::ASTC_5X4_UNORM_BLOCK,
+                AstcBlock::B5x5 => F::ASTC_5X5_UNORM_BLOCK,
+                AstcBlock::B6x5 => F::ASTC_6X5_UNORM_BLOCK,
+                AstcBlock::B6x6 => F::ASTC_6X6_UNORM_BLOCK,
+                AstcBlock::B8x5 => F::ASTC_8X5_UNORM_BLOCK,
+                AstcBlock::B8x6 => F::ASTC_8X6_UNORM_BLOCK,
+                AstcBlock::B8x8 => F::ASTC_8X8_UNORM_BLOCK,
+                AstcBlock::B10x5 => F::ASTC_10X5_UNORM_BLOCK,
+                AstcBlock::B10x6 => F::ASTC_10X6_UNORM_BLOCK,
+                AstcBlock::B10x8 => F::ASTC_10X8_UNORM_BLOCK,
+                AstcBlock::B10x10 => F::ASTC_10X10_UNORM_BLOCK,
+                AstcBlock::B12x10 => F::ASTC_12X10_UNORM_BLOCK,
+                AstcBlock::B12x12 => F::ASTC_12X12_UNORM_BLOCK,
+            },
+            AstcChannel::UnormSrgb => match block {
+                AstcBlock::B4x4 => F::ASTC_4X4_SRGB_BLOCK,
+                AstcBlock::B5x4 => F::ASTC_5X4_SRGB_BLOCK,
+                AstcBlock::B5x5 => F::ASTC_5X5_SRGB_BLOCK,
+                AstcBlock::B6x5 => F::ASTC_6X5_SRGB_BLOCK,
+                AstcBlock::B6x6 => F::ASTC_6X6_SRGB_BLOCK,
+                AstcBlock::B8x5 => F::ASTC_8X5_SRGB_BLOCK,
+                AstcBlock::B8x6 => F::ASTC_8X6_SRGB_BLOCK,
+                AstcBlock::B8x8 => F::ASTC_8X8_SRGB_BLOCK,
+                AstcBlock::B10x5 => F::ASTC_10X5_SRGB_BLOCK,
+                AstcBlock::B10x6 => F::ASTC_10X6_SRGB_BLOCK,
+                AstcBlock::B10x8 => F::ASTC_10X8_SRGB_BLOCK,
+                AstcBlock::B10x10 => F::ASTC_10X10_SRGB_BLOCK,
+                AstcBlock::B12x10 => F::ASTC_12X10_SRGB_BLOCK,
+                AstcBlock::B12x12 => F::ASTC_12X12_SRGB_BLOCK,
+            },
+            AstcChannel::Hdr => match block {
+                AstcBlock::B4x4 => F::ASTC_4X4_SFLOAT_BLOCK_EXT,
+                AstcBlock::B5x4 => F::ASTC_5X4_SFLOAT_BLOCK_EXT,
+                AstcBlock::B5x5 => F::ASTC_5X5_SFLOAT_BLOCK_EXT,
+                AstcBlock::B6x5 => F::ASTC_6X5_SFLOAT_BLOCK_EXT,
+                AstcBlock::B6x6 => F::ASTC_6X6_SFLOAT_BLOCK_EXT,
+                AstcBlock::B8x5 => F::ASTC_8X5_SFLOAT_BLOCK_EXT,
+                AstcBlock::B8x6 => F::ASTC_8X6_SFLOAT_BLOCK_EXT,
+                AstcBlock::B8x8 => F::ASTC_8X8_SFLOAT_BLOCK_EXT,
+                AstcBlock::B10x5 => F::ASTC_10X5_SFLOAT_BLOCK_EXT,
+                AstcBlock::B10x6 => F::ASTC_10X6_SFLOAT_BLOCK_EXT,
+                AstcBlock::B10x8 => F::ASTC_10X8_SFLOAT_BLOCK_EXT,
+                AstcBlock::B10x10 => F::ASTC_10X10_SFLOAT_BLOCK_EXT,
+                AstcBlock::B12x10 => F::ASTC_12X10_SFLOAT_BLOCK_EXT,
+                AstcBlock::B12x12 => F::ASTC_12X12_SFLOAT_BLOCK_EXT,
+            },
+        },
     }
 }

src/lib.rs

@@ -47,6 +47,7 @@ pub const RIGHT_XR_TEXTURE_HANDLE: ManualTextureViewHandle = ManualTextureViewHa
 
 /// Adds OpenXR support to an App
 pub struct OpenXrPlugin {
+    pub backend_preference: Vec<Backend>,
     pub reqeusted_extensions: XrExtensions,
     pub prefered_blend_mode: XrPreferdBlendMode,
     pub app_info: XrAppInfo,
@@ -59,6 +60,7 @@ impl Plugin for OpenXrPlugin {
         app.insert_resource(ExitAppOnSessionExit::default());
         #[cfg(not(target_arch = "wasm32"))]
         match graphics::initialize_xr_instance(
+            &self.backend_preference,
             SystemState::<Query<&RawHandleWrapper, With<PrimaryWindow>>>::new(&mut app.world)
                 .get(&app.world)
                 .get_single()
@@ -169,6 +171,17 @@ impl Plugin for OpenXrPlugin {
     }
 }
 
+#[cfg(all(not(feature = "vulkan"), not(all(feature = "d3d12", windows))))]
+compile_error!("At least one platform-compatible backend feature must be enabled.");
+
+#[derive(Debug)]
+pub enum Backend {
+    #[cfg(feature = "vulkan")]
+    Vulkan,
+    #[cfg(all(feature = "d3d12", windows))]
+    D3D12,
+}
+
 #[derive(Resource)]
 struct DoPipelinedRendering;
 
@@ -213,8 +226,9 @@ fn xr_skip_frame(
 ) {
     let swapchain: &Swapchain = &xr_swapchain;
     match swapchain {
-        Swapchain::Vulkan(swap) => {
+        #[cfg(feature = "vulkan")]
-            swap.stream
+        Swapchain::Vulkan(swap) => &swap
+            .stream
             .lock()
             .unwrap()
             .end(
@@ -222,12 +236,23 @@ fn xr_skip_frame(
                 **environment_blend_mode,
                 &[],
             )
-                .unwrap();
+            .unwrap(),
-        }
+        #[cfg(all(feature = "d3d12", windows))]
-    }
+        Swapchain::D3D12(swap) => &swap
+            .stream
+            .lock()
+            .unwrap()
+            .end(
+                xr_frame_state.predicted_display_time,
+                **environment_blend_mode,
+                &[],
+            )
+            .unwrap(),
+    };
 }
 
 pub struct DefaultXrPlugins {
+    pub backend_preference: Vec<Backend>,
     pub reqeusted_extensions: XrExtensions,
     pub prefered_blend_mode: XrPreferdBlendMode,
     pub app_info: XrAppInfo,
@@ -236,6 +261,12 @@ pub struct DefaultXrPlugins {
 impl Default for DefaultXrPlugins {
     fn default() -> Self {
         Self {
+            backend_preference: vec![
+                #[cfg(feature = "vulkan")]
+                Backend::Vulkan,
+                #[cfg(all(feature = "d3d12", windows))]
+                Backend::D3D12,
+            ],
             reqeusted_extensions: default(),
             prefered_blend_mode: default(),
             app_info: default(),
@@ -261,6 +292,7 @@ impl PluginGroup for DefaultXrPlugins {
             })
             .disable::<RenderPlugin>()
             .add_before::<RenderPlugin, _>(OpenXrPlugin {
+                backend_preference: self.backend_preference,
                 prefered_blend_mode: self.prefered_blend_mode,
                 reqeusted_extensions: self.reqeusted_extensions,
                 app_info: self.app_info.clone(),

src/passthrough.rs

@@ -195,17 +195,25 @@ pub fn supports_passthrough(instance: &XrInstance, system: xr::SystemId) -> xr::
 pub fn create_passthrough(
     xr_session: &XrSession,
 ) -> xr::Result<(xr::Passthrough, xr::PassthroughLayer)> {
+    let flags = xr::PassthroughFlagsFB::IS_RUNNING_AT_CREATION;
+    let purpose = xr::PassthroughLayerPurposeFB::RECONSTRUCTION;
     let passthrough = match xr_session {
+        #[cfg(feature = "vulkan")]
         XrSession::Vulkan(session) => {
             session.create_passthrough(xr::PassthroughFlagsFB::IS_RUNNING_AT_CREATION)
         }
+        #[cfg(all(feature = "d3d12", windows))]
+        XrSession::D3D12(session) => {
+            session.create_passthrough(xr::PassthroughFlagsFB::IS_RUNNING_AT_CREATION)
+        }
     }?;
     let passthrough_layer = match xr_session {
-        XrSession::Vulkan(session) => session.create_passthrough_layer(
+        #[cfg(feature = "vulkan")]
-            &passthrough,
+        XrSession::Vulkan(session) => {
-            xr::PassthroughFlagsFB::IS_RUNNING_AT_CREATION,
+            session.create_passthrough_layer(&passthrough, flags, purpose)
-            xr::PassthroughLayerPurposeFB::RECONSTRUCTION,
+        }
-        ),
+        #[cfg(all(feature = "d3d12", windows))]
+        XrSession::D3D12(session) => session.create_passthrough_layer(&passthrough, flags, purpose),
     }?;
     Ok((passthrough, passthrough_layer))
 }

src/resources.rs

@@ -14,6 +14,8 @@ use bevy::render::extract_component::ExtractComponent;
 use bevy::render::extract_resource::{ExtractResource, ExtractResourcePlugin};
 use core::ptr;
 use openxr as xr;
+#[cfg(all(feature = "d3d12", windows))]
+use winapi::um::d3d12::{ID3D12CommandQueue, ID3D12Device};
 
 xr_resource_wrapper!(XrInstance, xr::Instance);
 xr_resource_wrapper_copy!(XrEnvironmentBlendMode, xr::EnvironmentBlendMode);
@@ -27,7 +29,10 @@ xr_no_clone_resource_wrapper!(XrFrameWaiter, xr::FrameWaiter);
 
 #[derive(Clone, Resource, ExtractResource)]
 pub enum XrSession {
+    #[cfg(feature = "vulkan")]
     Vulkan(xr::Session<xr::Vulkan>),
+    #[cfg(all(feature = "d3d12", windows))]
+    D3D12(xr::Session<xr::D3D12>),
 }
 
 impl std::ops::Deref for XrSession {
@@ -37,12 +42,16 @@ impl std::ops::Deref for XrSession {
         // SAFTEY: should be fine i think -Schmarni
         unsafe {
             match self {
+                #[cfg(feature = "vulkan")]
                 XrSession::Vulkan(sess) => std::mem::transmute(sess),
+                #[cfg(all(feature = "d3d12", windows))]
+                XrSession::D3D12(sess) => std::mem::transmute(sess),
             }
         }
     }
 }
 
+#[cfg(feature = "vulkan")]
 pub struct VulkanOXrSessionSetupInfo {
     pub(crate) device_ptr: *const c_void,
     pub(crate) physical_device_ptr: *const c_void,
@@ -51,8 +60,18 @@ pub struct VulkanOXrSessionSetupInfo {
     pub(crate) xr_system_id: xr::SystemId,
 }
 
+#[cfg(all(feature = "d3d12", windows))]
+pub struct D3D12OXrSessionSetupInfo {
+    pub(crate) raw_device: *mut ID3D12Device,
+    pub(crate) raw_queue: *mut ID3D12CommandQueue,
+    pub(crate) xr_system_id: xr::SystemId,
+}
+
 pub enum OXrSessionSetupInfo {
+    #[cfg(feature = "vulkan")]
     Vulkan(VulkanOXrSessionSetupInfo),
+    #[cfg(all(feature = "d3d12", windows))]
+    D3D12(D3D12OXrSessionSetupInfo),
 }
 
 pub struct XrResourcePlugin;
@@ -72,37 +91,55 @@ impl Plugin for XrResourcePlugin {
 }
 
 pub enum Swapchain {
+    #[cfg(feature = "vulkan")]
     Vulkan(SwapchainInner<xr::Vulkan>),
+    #[cfg(all(feature = "d3d12", windows))]
+    D3D12(SwapchainInner<xr::D3D12>),
 }
 
 impl Swapchain {
     pub(crate) fn begin(&self) -> xr::Result<()> {
         match self {
+            #[cfg(feature = "vulkan")]
             Swapchain::Vulkan(swapchain) => swapchain.begin(),
+            #[cfg(all(feature = "d3d12", windows))]
+            Swapchain::D3D12(swapchain) => swapchain.begin(),
         }
     }
 
     pub(crate) fn get_render_views(&self) -> (wgpu::TextureView, wgpu::TextureView) {
         match self {
+            #[cfg(feature = "vulkan")]
             Swapchain::Vulkan(swapchain) => swapchain.get_render_views(),
+            #[cfg(all(feature = "d3d12", windows))]
+            Swapchain::D3D12(swapchain) => swapchain.get_render_views(),
         }
     }
 
     pub(crate) fn acquire_image(&self) -> xr::Result<()> {
         match self {
+            #[cfg(feature = "vulkan")]
             Swapchain::Vulkan(swapchain) => swapchain.acquire_image(),
+            #[cfg(all(feature = "d3d12", windows))]
+            Swapchain::D3D12(swapchain) => swapchain.acquire_image(),
         }
     }
 
     pub(crate) fn wait_image(&self) -> xr::Result<()> {
         match self {
+            #[cfg(feature = "vulkan")]
             Swapchain::Vulkan(swapchain) => swapchain.wait_image(),
+            #[cfg(all(feature = "d3d12", windows))]
+            Swapchain::D3D12(swapchain) => swapchain.wait_image(),
         }
     }
 
     pub(crate) fn release_image(&self) -> xr::Result<()> {
         match self {
+            #[cfg(feature = "vulkan")]
             Swapchain::Vulkan(swapchain) => swapchain.release_image(),
+            #[cfg(all(feature = "d3d12", windows))]
+            Swapchain::D3D12(swapchain) => swapchain.release_image(),
         }
     }
 
@@ -116,6 +153,7 @@ impl Swapchain {
         passthrough_layer: Option<&XrPassthroughLayer>,
     ) -> xr::Result<()> {
         match self {
+            #[cfg(feature = "vulkan")]
             Swapchain::Vulkan(swapchain) => swapchain.end(
                 predicted_display_time,
                 views,
@@ -124,6 +162,15 @@ impl Swapchain {
                 environment_blend_mode,
                 passthrough_layer,
             ),
+            #[cfg(all(feature = "d3d12", windows))]
+            Swapchain::D3D12(swapchain) => swapchain.end(
+                predicted_display_time,
+                views,
+                stage,
+                resolution,
+                environment_blend_mode,
+                passthrough_layer,
+            ),
         }
     }
 }