Hash :
8d4331ee
Author :
Date :
2020-09-16T00:42:08
Vulkan: Free up 5 bits in RenderPassDesc Leveraging the fact that there are only a handful of depth/stencil formats, the last element of RenderPassDesc::mAttachmentFormats can contain other information in addition to the depth/stencil format ID. The FormatID enum is rearranged such that depth/stencil formats are placed first, as a result occupying values in [1, 7]. These values take up 3 bits in an element of RenderPassDesc::mAttachmentFormats (which could be the last element if all color draw buffers are attached). As a result, the upper 5 bits of the last element of RenderPassDesc::mAttachmentFormats is unused. It is intended for these bits to be used in the implementation of multisampled-render-to-texture depth/stencil renderbuffers. Bug: angleproject:4836 Change-Id: I0786e0712539cdbbf5494ec83aeee1dd93f936dd Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2413165 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Tim Van Patten <timvp@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>
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:
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.
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.
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);
More implementation details can be found in the doc directory: