Table of Contents

Synchronization

Synchronization makes data produced by earlier GPU work available to later work. Choose the mechanism that matches the dependency:

Mechanism Use it when
Barrier(before, after) Commands in one command buffer share data without changing a texture layout
Transition(texture, subresource, before, after) A texture changes its access role
Submit(waitValues...) A submission depends on work submitted to another queue

Add a Memory Barrier

Use Barrier when a later command consumes memory written by an earlier command and the resource layout does not change:

commandBuffer.SetPipeline(pipeline);
commandBuffer.Dispatch(groupCount, 1, 1);

commandBuffer.Barrier(BarrierStages.ComputeShading, BarrierStages.ComputeShading);

commandBuffer.SetPipeline(nextPipeline);
commandBuffer.Dispatch(nextGroupCount, 1, 1);

Common cases include storage-buffer producer/consumer chains and compute-generated indirect arguments. Select the stages that perform the producing and consuming work, and combine flags when several stages consume the result.

Use BarrierStages.All only when a narrower dependency cannot describe the work.

Transition a Texture

Supply the current and next layout whenever a texture changes how it is used:

commandBuffer.Transition(texture, default, TextureLayout.Undefined, TextureLayout.Storage);

commandBuffer.SetPipeline(pipeline);
commandBuffer.SetConstantBuffer(buffer, 0);
commandBuffer.Dispatch(groupCountX, groupCountY, 1);

commandBuffer.Transition(texture, default, TextureLayout.Storage, TextureLayout.Sampled);

default selects mip level zero and array layer zero. Pass a TextureSubresource with the required MipLevel and ArrayLayer when another subresource is needed.

Use Undefined as the source only when previous contents can be discarded. Copy, resolve, and command-buffer upload or download operations do not insert transitions. The Texture.Upload and Texture.Download convenience methods perform their declared current-to-final layout transitions.

The principal layouts are listed in declaration order:

Layout Access role
Undefined Previous contents are discarded
Common General access and shared-texture presentation paths
Sampled Sampled texture reads
Storage Storage texture reads and writes
ColorAttachment Color attachment access
DepthStencilAttachment Writable depth/stencil attachment access
DepthStencilReadOnly Read-only depth/stencil access
CopySrc / CopyDst Copy source or destination
ResolveSrc / ResolveDst Resolve source or destination
Present Presentation

Order Work Across Queues

Pass a producer's TimelineValue to the dependent submission:

CommandBuffer commandBuffer = context.TransferQueue.CommandBuffer();
commandBuffer.Upload(buffer, 0, data);
TimelineValue timelineValue = commandBuffer.Submit();

commandBuffer = context.ComputeQueue.CommandBuffer();
commandBuffer.SetPipeline(pipeline);
commandBuffer.SetConstantBuffer(buffer, 0);
commandBuffer.Dispatch(groupCountX, groupCountY, 1);

commandBuffer.Submit(timelineValue);

Passing a producer TimelineValue to Submit orders the consumer submission after that value without blocking the CPU. Call Wait() only when CPU code must observe GPU results.

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