d3d12 超大图片渲染纹理切割代码

以下是使用DirectX 12渲染超大纹理并进行切割的代码示例：

首先，需要创建一个用于渲染的纹理对象：

D3D12_HEAP_PROPERTIES heapProps = CD3DX12_HEAP_PROPERTIES(D3D12_HEAP_TYPE_DEFAULT);
D3D12_RESOURCE_DESC resDesc = CD3DX12_RESOURCE_DESC::Tex2D(format, width, height, 1, mipLevels);
resDesc.Flags |= D3D12_RESOURCE_FLAG_ALLOW_RENDER_TARGET;
resDesc.Flags |= D3D12_RESOURCE_FLAG_ALLOW_UNORDERED_ACCESS;

ThrowIfFailed(device->CreateCommittedResource(
    &heapProps,
    D3D12_HEAP_FLAG_NONE,
    &resDesc,
    D3D12_RESOURCE_STATE_RENDER_TARGET,
    nullptr,
    IID_PPV_ARGS(&m_RenderTarget)));

然后，可以使用此纹理对象创建一个渲染目标视图：

D3D12_RENDER_TARGET_VIEW_DESC rtvDesc = {};
rtvDesc.Format = format;
rtvDesc.ViewDimension = D3D12_RTV_DIMENSION_TEXTURE2D;

CD3DX12_CPU_DESCRIPTOR_HANDLE rtvHandle(m_RTVDescriptorHeap->GetCPUDescriptorHandleForHeapStart(), m_frameIndex, m_RTVDescriptorSize);
device->CreateRenderTargetView(m_RenderTarget.Get(), &rtvDesc, rtvHandle);

接下来，可以使用此纹理对象创建一个无序访问视图：

D3D12_UNORDERED_ACCESS_VIEW_DESC uavDesc = {};
uavDesc.Format = format;
uavDesc.ViewDimension = D3D12_UAV_DIMENSION_TEXTURE2D;
uavDesc.Texture2D.MipSlice = 0;

CD3DX12_CPU_DESCRIPTOR_HANDLE uavHandle(m_UAVDescriptorHeap->GetCPUDescriptorHandleForHeapStart(), m_frameIndex, m_UAVDescriptorSize);
device->CreateUnorderedAccessView(m_RenderTarget.Get(), nullptr, &uavDesc, uavHandle);

现在，可以使用渲染目标和无序访问视图进行渲染。例如，可以将纹理切割成多个小纹理，每个小纹理的大小为256x256：

const int nTilesX = (width + 255) / 256;
const int nTilesY = (height + 255) / 256;

for (int y = 0; y < nTilesY; ++y)
{
    for (int x = 0; x < nTilesX; ++x)
    {
        // Set viewport and scissor rect for current tile
        D3D12_VIEWPORT viewport = { x * 256.0f, y * 256.0f, 256.0f, 256.0f, 0.0f, 1.0f };
        D3D12_RECT scissorRect = { x * 256, y * 256, (x + 1) * 256, (y + 1) * 256 };

        // Set render target and clear color
        D3D12_CPU_DESCRIPTOR_HANDLE rtvHandle(m_RTVDescriptorHeap->GetCPUDescriptorHandleForHeapStart(), m_frameIndex, m_RTVDescriptorSize);
        device->OMSetRenderTargets(1, &rtvHandle, FALSE, nullptr);
        float clearColor[] = { 0.0f, 0.0f, 0.0f, 1.0f };
        commandList->ClearRenderTargetView(rtvHandle, clearColor, 0, nullptr);

        // Draw using current viewport and scissor rect
        commandList->RSSetViewports(1, &viewport);
        commandList->RSSetScissorRects(1, &scissorRect);
        // Draw code goes here
    }
}

最后，需要将渲染目标的内容拷贝到CPU可访问的纹理中：

D3D12_RESOURCE_BARRIER barrier = CD3DX12_RESOURCE_BARRIER::Transition(m_RenderTarget.Get(), D3D12_RESOURCE_STATE_RENDER_TARGET, D3D12_RESOURCE_STATE_COPY_SOURCE);
commandList->ResourceBarrier(1, &barrier);

CD3DX12_TEXTURE_COPY_LOCATION src(m_RenderTarget.Get(), 0);
CD3DX12_TEXTURE_COPY_LOCATION dst(m_StagingTexture.Get(), D3D12CalcSubresource(0, 0, 1));
commandList->CopyTextureRegion(&dst, 0, 0, 0, &src, nullptr);

barrier = CD3DX12_RESOURCE_BARRIER::Transition(m_RenderTarget.Get(), D3D12_RESOURCE_STATE_COPY_SOURCE, D3D12_RESOURCE_STATE_RENDER_TARGET);
commandList->ResourceBarrier(1, &barrier);

这样就可以使用DirectX 12渲染超大纹理并进行切割了。