针对 Rift 进行渲染

// Configure Stereo settings.
Sizei recommenedTex0Size = ovr_GetFovTextureSize(session, ovrEye_Left,
   session->DefaultEyeFov[0], 1.0f);
Sizei recommenedTex1Size = ovr_GetFovTextureSize(session, ovrEye_Right,
   session->DefaultEyeFov[1], 1.0f);
Sizei bufferSize;
bufferSize.w  = recommenedTex0Size.w + recommenedTex1Size.w;
bufferSize.h = max ( recommenedTex0Size.h, recommenedTex1Size.h );

static const uint32_t AMDVendorId = 0x1002;
isAMD = (gpuProps.vendorID == AMDVendorId);

static const char* deviceExtensions[] =
{
   VK_KHR_SWAPCHAIN_EXTENSION_NAME,
   VK_KHX_EXTERNAL_MEMORY_EXTENSION_NAME,
   #if defined(VK_USE_PLATFORM_WIN32_KHR)
      VK_KHX_EXTERNAL_MEMORY_WIN32_EXTENSION_NAME,
   #endif
};

static const char* deviceExtensionsAMD[] =
{
  VK_KHR_SWAPCHAIN_EXTENSION_NAME
};

ovrTextureSwapChain textureSwapChain = 0;

ovrTextureSwapChainDesc desc = {};
desc.Type = ovrTexture_2D;
desc.ArraySize = 1;
desc.Format = OVR_FORMAT_R8G8B8A8_UNORM_SRGB;
desc.Width = bufferSize.w;
desc.Height = bufferSize.h;
desc.MipLevels = 1;
desc.SampleCount = 1;
desc.StaticImage = ovrFalse;

if (ovr_CreateTextureSwapChainGL(session, &desc, &textureSwapChain) == ovrSuccess)
{
    // Sample texture access:
    int texId;
    ovr_GetTextureSwapChainBufferGL(session, textureSwapChain, 0, &texId);
    glBindTexture(GL_TEXTURE_2D, texId);
    ...
}

ovrTextureSwapChain textureSwapChain = 0;
std::vector<ID3D11RenderTargetView*> texRtv;

ovrTextureSwapChainDesc desc = {};
desc.Type = ovrTexture_2D;
desc.Format = OVR_FORMAT_R8G8B8A8_UNORM_SRGB;
desc.ArraySize = 1;
desc.Width = bufferSize.w;
desc.Height = bufferSize.h;
desc.MipLevels = 1;
desc.SampleCount = 1;
desc.StaticImage = ovrFalse;
desc.MiscFlags = ovrTextureMisc_None;
desc.BindFlags = ovrTextureBind_DX_RenderTarget;

 if (ovr_CreateTextureSwapChainDX(session, DIRECTX.Device, &desc, &textureSwapChain) == ovrSuccess)
 {
     int count = 0;
     ovr_GetTextureSwapChainLength(session, textureSwapChain, &count);
     texRtv.resize(textureCount);
     for (int i = 0; i < count; ++i)
     {
         ID3D11Texture2D* texture = nullptr;
         ovr_GetTextureSwapChainBufferDX(session, textureSwapChain, i, IID_PPV_ARGS(&texture));
         DIRECTX.Device->CreateRenderTargetView(texture, nullptr, &texRtv[i]);
         texture->Release();
     }
 }

ovrTextureSwapChain TexChain;
std::vector<D3D12_CPU_DESCRIPTOR_HANDLE> texRtv;
std::vector<ID3D12Resource*> TexResource;

ovrTextureSwapChainDesc desc = {};
desc.Type = ovrTexture_2D;
desc.ArraySize = 1;
desc.Format = OVR_FORMAT_R8G8B8A8_UNORM_SRGB;
desc.Width = sizeW;
desc.Height = sizeH;
desc.MipLevels = 1;
desc.SampleCount = 1;
desc.MiscFlags = ovrTextureMisc_DX_Typeless;
desc.StaticImage = ovrFalse;
desc.BindFlags = ovrTextureBind_DX_RenderTarget;

// DIRECTX.CommandQueue is the ID3D12CommandQueue used to render the eye textures by the app
ovrResult result = ovr_CreateTextureSwapChainDX(session, DIRECTX.CommandQueue, &desc, &TexChain);
if (!OVR_SUCCESS(result))
    return false;

int textureCount = 0;
ovr_GetTextureSwapChainLength(Session, TexChain, &textureCount);
texRtv.resize(textureCount);
TexResource.resize(textureCount);
for (int i = 0; i < textureCount; ++i)
{
    result = ovr_GetTextureSwapChainBufferDX(Session, TexChain, i, IID_PPV_ARGS(&TexResource[i]));
    if (!OVR_SUCCESS(result))
        return false;

    D3D12_RENDER_TARGET_VIEW_DESC rtvd = {};
    rtvd.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
    rtvd.ViewDimension = D3D12_RTV_DIMENSION_TEXTURE2D;
    texRtv[i] = DIRECTX.RtvHandleProvider.AllocCpuHandle(); // Gives new D3D12_CPU_DESCRIPTOR_HANDLE
    DIRECTX.Device->CreateRenderTargetView(TexResource[i], &rtvd, texRtv[i]);
}

bool Create(ovrSession aSession, VkExtent2D aSize, RenderPass& renderPass, DepthBuffer& depthBuffer)
{
    session = aSession;
    size = aSize;

    ovrTextureSwapChainDesc desc = {};
    desc.Type = ovrTexture_2D;
    desc.ArraySize = 1;
    desc.Format = OVR_FORMAT_R8G8B8A8_UNORM_SRGB;
    desc.Width = (int)size.width;
    desc.Height = (int)size.height;
    desc.MipLevels = 1;
    desc.SampleCount = 1;
    desc.MiscFlags = ovrTextureMisc_DX_Typeless;
    desc.BindFlags = ovrTextureBind_DX_RenderTarget;
    desc.StaticImage = ovrFalse;

    ovrResult result = ovr_CreateTextureSwapChainVk(session, Platform.device, &desc, &textureChain);
    if (!OVR_SUCCESS(result))
        return false;

    int textureCount = 0;
    ovr_GetTextureSwapChainLength(session, textureChain, &textureCount);
    texElements.reserve(textureCount);
    for (int i = 0; i < textureCount; ++i)
    {
        VkImage image;
        result = ovr_GetTextureSwapChainBufferVk(session, textureChain, i, &image);
        texElements.emplace_back(RenderTexture());
        CHECK(texElements.back().Create(image, VK_FORMAT_R8G8B8A8_SRGB, size, renderPass, depthBuffer.view));
   }

    return true;
}

ovrTextureSwapChainDesc desc = {};
desc.Type = ovrTexture_2D;
desc.ArraySize = 1;
desc.Format = OVR_FORMAT_R8G8B8A8_UNORM_SRGB;
desc.Width = sizeW;
desc.Height = sizeH;
desc.MipLevels = 1;
desc.SampleCount = 1;
desc.MiscFlags = ovrTextureMisc_DX_Typeless;
desc.BindFlags = ovrTextureBind_DX_RenderTarget;
desc.StaticImage = ovrFalse;

ovrResult result = ovr_CreateTextureSwapChainDX(session, DIRECTX.Device, &desc, &textureSwapChain);

if(!OVR_SUCCESS(result))
    return;

int count = 0;
ovr_GetTextureSwapChainLength(session, textureSwapChain, &count);
for (int i = 0; i < count; ++i)
{
    ID3D11Texture2D* texture = nullptr;
    ovr_GetTextureSwapChainBufferDX(session, textureSwapChain, i, IID_PPV_ARGS(&texture));
    D3D11_RENDER_TARGET_VIEW_DESC rtvd = {};
    rtvd.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
    rtvd.ViewDimension = D3D11_RTV_DIMENSION_TEXTURE2D;
    DIRECTX.Device->CreateRenderTargetView(texture, &rtvd, &texRtv[i]);
    texture->Release();
}

 // Initialize VR structures, filling out description.
ovrEyeRenderDesc eyeRenderDesc[2];
ovrPosef      hmdToEyeViewPose[2];
ovrHmdDesc hmdDesc = ovr_GetHmdDesc(session);
eyeRenderDesc[0] = ovr_GetRenderDesc(session, ovrEye_Left, hmdDesc.DefaultEyeFov[0]);
eyeRenderDesc[1] = ovr_GetRenderDesc(session, ovrEye_Right, hmdDesc.DefaultEyeFov[1]);
hmdToEyeViewPose[0] = eyeRenderDesc[0].HmdToEyePose;
hmdToEyeViewPose[1] = eyeRenderDesc[1].HmdToEyePose;

// Initialize our single full screen Fov layer.
ovrLayerEyeFov layer;
layer.Header.Type      = ovrLayerType_EyeFov;
layer.Header.Flags     = 0;
layer.ColorTexture[0]  = textureSwapChain;
layer.ColorTexture[1]  = textureSwapChain;
layer.Fov[0]           = eyeRenderDesc[0].Fov;
layer.Fov[1]           = eyeRenderDesc[1].Fov;
layer.Viewport[0]      = Recti(0, 0,                bufferSize.w / 2, bufferSize.h);
layer.Viewport[1]      = Recti(bufferSize.w / 2, 0, bufferSize.w / 2, bufferSize.h);
// ld.RenderPose and ld.SensorSampleTime are updated later per frame.

// Get both eye poses simultaneously, with IPD offset already included.
double displayMidpointSeconds = ovr_GetPredictedDisplayTime(session, 0);
ovrTrackingState hmdState = ovr_GetTrackingState(session, displayMidpointSeconds, ovrTrue);
ovr_CalcEyePoses(hmdState.HeadPose.ThePose, hmdToEyeViewPose, layer.RenderPose);

if (isVisible)
{
  // Get next available index of the texture swap chain
    int currentIndex = 0;
    ovr_GetTextureSwapChainCurrentIndex(session, textureSwapChain, &currentIndex);
    ++frameIndex;
    ovrResult result = ovr_WaitToBeginFrame(session, frameIndex);

    // Clear and set up render-target.
    DIRECTX.SetAndClearRenderTarget(pTexRtv[currentIndex], pEyeDepthBuffer);

    // Render Scene to Eye Buffers
    result = ovr_BeginFrame(session, frameIndex);
    for (int eye = 0; eye < 2; eye++)
    {
        // Get view and projection matrices for the Rift camera
        Vector3f pos = originPos + originRot.Transform(layer.RenderPose[eye].Position);
        Matrix4f rot = originRot * Matrix4f(layer.RenderPose[eye].Orientation);

        Vector3f finalUp      = rot.Transform(Vector3f(0, 1, 0));
        Vector3f finalForward = rot.Transform(Vector3f(0, 0, -1));
        Matrix4f view         = Matrix4f::LookAtRH(pos, pos + finalForward, finalUp);

        Matrix4f proj = ovrMatrix4f_Projection(layer.Fov[eye], 0.2f, 1000.0f, 0);
        // Render the scene for this eye.
        DIRECTX.SetViewport(layer.Viewport[eye]);
        roomScene.Render(proj * view, 1, 1, 1, 1, true);
    }

  // Commit the changes to the texture swap chain
  ovr_CommitTextureSwapChain(session, textureSwapChain);
}

// Submit frame with one layer we have.
ovrLayerHeader* layers = &layer.Header;
result = ovr_EndFrame(session, frameIndex, nullptr, &layers, 1);
isVisible = (result == ovrSuccess);

ovr_GetPredictedDisplayTime(ovrSession session, long long frameIndex);

void MainThreadProcessing()
{
    frameIndex++;
    ovrResult result = ovr_WaitToBeginFrame(session, frameIndex);

    // Ask the API for the times when this frame is expected to be displayed.
    double frameTiming = ovr_GetPredictedDisplayTime(session, frameIndex);

    // Get the corresponding predicted pose state.
    ovrTrackingState state = ovr_GetTrackingState(session, frameTiming, ovrTrue);
    ovrPosef         eyePoses[2];
    ovr_CalcEyePoses(state.HeadPose.ThePose, hmdToEyeViewOffset, eyePoses);

    SetFrameHMDData(frameIndex, eyePoses);

    // Do render pre-processing for this frame.
    ...
}

void RenderThreadProcessing()
{
    int       frameIndex;
    ovrPosef  eyePoses[2];
    GetFrameHMDData(&frameIndex, eyePoses);
    ovrResult result = ovr_BeginFrame(session, frameIndex);

    layer.RenderPose[0] = eyePoses[0];
    layer.RenderPose[1] = eyePoses[1];

    // Execute actual rendering to eye textures.
    ...

   // Submit frame with the one layer we have.
   ovrLayerHeader* layers = &layer.Header;
   result = ovr_EndFrame(session, frameIndex, nullptr, &layers, 1);
}

ovrResult result = ovr_WaitToBeginFrame(Session, frameIndex);
result = ovr_BeginFrame(Session, frameIndex);
// Create eye layer.
ovrLayerEyeFov eyeLayer;
eyeLayer.Header.Type    = ovrLayerType_EyeFov;
eyeLayer.Header.Flags   = 0;
for ( int eye = 0; eye < 2; eye++ )
{
  eyeLayer.ColorTexture[eye] = EyeBufferSet[eye];
  eyeLayer.Viewport[eye]     = EyeViewport[eye];
  eyeLayer.Fov[eye]          = EyeFov[eye];
  eyeLayer.RenderPose[eye]   = EyePose[eye];
}

// Create HUD layer, fixed to the player's torso
ovrLayerQuad hudLayer;
hudLayer.Header.Type    = ovrLayerType_Quad;
hudLayer.Header.Flags   = ovrLayerFlag_HighQuality;
hudLayer.ColorTexture   = TheHudTextureSwapChain;
// 50cm in front and 20cm down from the player's nose,
// fixed relative to their torso.
hudLayer.QuadPoseCenter.Position.x =  0.00f;
hudLayer.QuadPoseCenter.Position.y = -0.20f;
hudLayer.QuadPoseCenter.Position.z = -0.50f;
hudLayer.QuadPoseCenter.Orientation.x = 0;
hudLayer.QuadPoseCenter.Orientation.y = 0;
hudLayer.QuadPoseCenter.Orientation.z = 0;
hudLayer.QuadPoseCenter.Orientation.w = 1;
// HUD is 50cm wide, 30cm tall.
hudLayer.QuadSize.x = 0.50f;
hudLayer.QuadSize.y = 0.30f;

ID3D11Texture2D* tex = nullptr;
ovr_GetTextureSwapChainBufferDX(Session, TheHudTextureSwapChain, 0, IID_PPV_ARGS(&tex));
D3D11_TEXTURE2D_DESC desc;
tex->GetDesc(&desc);
// Display all of the HUD texture.
hudLayer.Viewport.Pos.x = 0.0f;
hudLayer.Viewport.Pos.y = 0.0f;
hudLayer.Viewport.Size.w = desc.Width;
hudLayer.Viewport.Size.h = desc.Height;

// The list of layers.
ovrLayerHeader *layerList[2];
layerList[0] = &eyeLayer.Header;
layerList[1] = &hudLayer.Header;

// Set up positional data.
ovrViewScaleDesc viewScaleDesc;
viewScaleDesc.HmdSpaceToWorldScaleInMeters = 1.0f;
viewScaleDesc.HmdToEyeViewOffset[0] = HmdToEyePose[0];
viewScaleDesc.HmdToEyeViewOffset[1] = HmdToEyePose[1];

result = ovr_EndFrame(Session, frameIndex, &viewScaleDesc, layerList, 2);

ovrResult result = ovr_WaitToBeginFrame(Hmd, frameIndex);
result = ovr_BeginFrame(Hmd, frameIndex);
// Create two TextureSwapChains to illustrate.
ovrTextureSwapChain eyeTextureSwapChain;
ovr_CreateTextureSwapChainDX ( ... &eyeTextureSwapChain );
ovrTextureSwapChain hudTextureSwapChain;
ovr_CreateTextureSwapChainDX ( ... &hudTextureSwapChain );

// Set up two layers.
ovrLayerEyeFov eyeLayer;
ovrLayerEyeFov hudLayer;
eyeLayer.Header.Type = ovrLayerType_EyeFov;
eyeLayer...etc... // set up the rest of the data.
hudLayer.Header.Type = ovrLayerType_Quad;
hudLayer...etc... // set up the rest of the data.

// the list of layers
ovrLayerHeader *layerList[2];
layerList[0] = &eyeLayer.Header;
layerList[1] = &hudLayer.Header;

// Each frame...
int currentIndex = 0;
ovr_GetTextureSwapChainCurrentIndex(... eyeTextureSwapChain, &currentIndex);
// Render into it. It is recommended the app use ovr_GetTextureSwapChainBufferDX for each index on texture chain creation to cache
// textures or create matching render target views. Each frame, the currentIndex value returned can be used to index directly into that.
ovr_CommitTextureSwapChain(... eyeTextureSwapChain);

ovr_GetTextureSwapChainCurrentIndex(... hudTextureSwapChain, &currentIndex);
// Render into it. It is recommended the app use ovr_GetTextureSwapChainBufferDX for each index on texture chain creation to cache
// textures or create matching render target views. Each frame, the currentIndex value returned can be used to index directly into that.
ovr_CommitTextureSwapChain(... hudTextureSwapChain);

eyeLayer.ColorTexture[0] = eyeTextureSwapChain;
eyeLayer.ColorTexture[1] = eyeTextureSwapChain;
hudLayer.ColorTexture = hudTextureSwapChain;

result = ovr_EndFrame(Hmd, frameIndex, nullptr, layerList, 2);