Direct3D 12 尝鲜(二): Fence

曾经终败给现在 2022-08-07 09:59 156阅读 0赞

###### (转载请注明出处) ######

正如[上节][Link 1]末尾所说, 出现了运行时**错误**:

**D3D12 ERROR: ID3D12CommandAllocator::Reset: A command allocator is being reset before previous executions associated with the allocator have completed. \[ EXECUTION ERROR \#548: COMMAND\_ALLOCATOR\_SYNC\]**

就是说要在相关执行完成后才能重置, 在自己的第一印象中, 认为提交呈现(Present)后, 所有的操纵就完成了, 但这样似乎不是这样的, 微软在[这里][Link 2]有提到:

> Waiting for frame rendering is probably the coarsest way to be certain that the GPU has finished. At a finer grain, you can again use fences

就是说, 等待帧渲染完毕就认为GPU工作完毕了, 这种做法不够好, 最好使用Fence:  
![篱笆][20150330220758496]

好了, 篱笆来了, 路障来了, 微软你不再来个钉刺带?╮（￣▽￣）╭

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Fence对应的接口就是[ID3D12Fence][]了,可以利用[ID3D12Device::CreateFence][ID3D12Device_CreateFence]创建这个接口, 具体代码就不累述了, 很简单.  
这个Fence是以帧为单位的, 可以等待所有针对这一帧的命令.利用[ID3D12Fence::SetEventOnCompletion][ID3D12Fence_SetEventOnCompletion]和[ID3D12CommandQueue::Signal][ID3D12CommandQueue_Signal]进行信号操作, 完了之后等待即可, 以帧为单位。  
不过还有个[ID3D12Fence::Signal][ID3D12Fence_Signal], 看来有**可能**[ID3D12CommandQueue::Signal][ID3D12CommandQueue_Signal]会调用这个方法, 否则这个Fence没有能与命令绑定的方法.

### **所以大致渲染流程就是:** ###

1.  Fence -> SetEventOnCompletion
2.  执行命令
3.  提交呈现
4.  Queue -> Signal
5.  WaitForXXXXXXXObject

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结合上次, 这次就很简单了. 还有就是我试了下**将3放在5后面**, 也(**貌似?**)没问题, 不过根据微软的表述, 还是放在Signal前面.

#### 所附代码下载: ####

[点击这里][Link 3]

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[Link 1]: http://blog.csdn.net/dustpg/article/details/44729071
[Link 2]: https://msdn.microsoft.com/en-us/library/windows/desktop/dn899206%28v=vs.85%29.aspx
[20150330220758496]: /images/20220805/ff42958a7ab64e79bdaaa54ac5616777.png
[ID3D12Fence]: https://msdn.microsoft.com/en-us/library/windows/desktop/dn899188%28v=vs.85%29.aspx
[ID3D12Device_CreateFence]: https://msdn.microsoft.com/en-us/library/windows/desktop/dn899179%28v=vs.85%29.aspx
[ID3D12Fence_SetEventOnCompletion]: https://msdn.microsoft.com/en-us/library/windows/desktop/dn899190%28v=vs.85%29.aspx
[ID3D12CommandQueue_Signal]: https://msdn.microsoft.com/en-us/library/windows/desktop/dn899171%28v=vs.85%29.aspx
[ID3D12Fence_Signal]: https://msdn.microsoft.com/en-us/library/windows/desktop/dn899191%28v=vs.85%29.aspx
[Link 3]: http://download.csdn.net/detail/dustpg/8548763