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  • Hash : d59bccb5
    Author : Charlie Lao
    Date : 2020-09-23T10:20:35

    Vulkan: updateRenderPassDesc may lose color attachment data
    
    FramebufferVk::updateRenderPassDesc() is resetting entire
    mRenderPassDesc, which may lose color unresolve attachments. This CL
    makes sure that when we toggle depth stencil buffer's read/write access,
    we do not reset the whole mRenderPassDesc. Instead we only update the
    depth stencil attachment's access.
    
    Bug: b/168953278
    Change-Id: Ia9df2d8ac81ebf2da8a360ba1293faf6c14b2738
    Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2426468
    Commit-Queue: Charlie Lao <cclao@google.com>
    Reviewed-by: Jamie Madill <jmadill@chromium.org>
    Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
    Reviewed-by: Tim Van Patten <timvp@google.com>
    

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    Description

    A conformant OpenGL ES implementation for Windows, Mac, Linux, iOS and Android.

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  • README.md

  • ANGLE: Vulkan Back-end

    ANGLE’s Vulkan back-end implementation lives in this folder.

    Vulkan is an explicit graphics API. It has a lot in common with other explicit APIs such as Microsoft’s D3D12 and Apple’s Metal. Compared to APIs like OpenGL or D3D11 explicit APIs can offer a number of significant benefits:

    • Lower API call CPU overhead.
    • A smaller API surface with more direct hardware control.
    • Better support for multi-core programming.
    • Vulkan in particular has open-source tooling and tests.

    Back-end Design

    The RendererVk class represents an EGLDisplay. RendererVk owns shared global resources like the VkDevice, VkQueue, the Vulkan format tables and internal Vulkan shaders. The ContextVk class implements the back-end of a front-end OpenGL Context. ContextVk processes state changes and handles action commands like glDrawArrays and glDrawElements.

    Command recording

    The back-end records commands into command buffers via the the following ContextVk APIs:

    • getOutsideRenderPassCommandBuffer: returns a secondary command buffer outside a RenderPass instance.
    • flushAndBeginRenderPass: returns a secondary command buffer inside a RenderPass instance.

    Note: All of these commands may write out (aka flush) prior pending commands into a primary command buffer. When a RenderPass is open getOutsideRenderPassCommandBuffer will flush the pending RenderPass commands. flushAndBeginRenderPass will flush out pending commands outside a RenderPass to a primary buffer. On submit ANGLE submits the primary command buffer to a VkQueue.

    If you need to record inside a RenderPass, use flushAndBeginRenderPass. Otherwise, use getOutsideRenderPassCommandBuffer.

    The back-end (mostly) records Image and Buffer barriers through additional ContextVk APIs:

    • onBufferTransferRead and onBufferComputeShaderRead accumulate VkBuffer read barriers.
    • onBufferTransferWrite and onBufferComputeShaderWrite accumulate VkBuffer write barriers.
    • onBuffferSelfCopy is a special case for VkBuffer self copies. It behaves the same as write.
    • onImageTransferRead and onImageComputerShadeRead accumulate VkImage read barriers.
    • onImageTransferWrite and onImageComputerShadeWrite accumulate VkImage write barriers.
    • onImageRenderPassRead and onImageRenderPassWrite accumulate VkImage barriers inside a started RenderPass.

    After the back-end records commands to the primary buffer we flush (e.g. on swap) or when we call ContextVk::finishToSerial.

    See the code for more details.

    Simple command recording example

    In this example we’ll be recording a buffer copy command:

        # Ensure that ANGLE sets proper read and write barriers for the Buffers.
        ANGLE_TRY(contextVk->onBufferTransferWrite(destBuffer));
        ANGLE_TRY(contextVk->onBufferTransferRead(srcBuffer));
    
        # Get a pointer to a secondary command buffer for command recording. May "flush" the RP.
        vk::CommandBuffer *commandBuffer;
        ANGLE_TRY(contextVk->getOutsideRenderPassCommandBuffer(&commandBuffer));
    
        # Record the copy command into the secondary buffer. We're done!
        commandBuffer->copyBuffer(srcBuffer->getBuffer(), destBuffer->getBuffer(), copyCount, copies);

    Additional Reading

    More implementation details can be found in the doc directory: