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• ### Similar Content

• By lubbe75
As far as I understand there is no real random or noise function in HLSL.
I have a big water polygon, and I'd like to fake water wave normals in my pixel shader. I know it's not efficient and the standard way is really to use a pre-calculated noise texture, but anyway...
Does anyone have any quick and dirty HLSL shader code that fakes water normals, and that doesn't look too repetitious?

• Hi,
I finally managed to get the DX11 emulating Vulkan device working but everything is flipped vertically now because Vulkan has a different clipping space. What are the best practices out there to keep these implementation consistent? I tried using a vertically flipped viewport, and while it works on Nvidia 1050, the Vulkan debug layer is throwing error messages that this is not supported in the spec so it might not work on others. There is also the possibility to flip the clip scpace position Y coordinate before writing out with vertex shader, but that requires changing and recompiling every shader. I could also bake it into the camera projection matrices, though I want to avoid that because then I need to track down for the whole engine where I upload matrices... Any chance of an easy extension or something? If not, I will probably go with changing the vertex shaders.
• By NikiTo
Some people say "discard" has not a positive effect on optimization. Other people say it will at least spare the fetches of textures.

if (color.A < 0.1f) { //discard; clip(-1); } // tons of reads of textures following here // and loops too
Some people say that "discard" will only mask out the output of the pixel shader, while still evaluates all the statements after the "discard" instruction.

MSN>
discard: Do not output the result of the current pixel.
<MSN

As usual it is unclear, but it suggests that "clip" could discard the whole pixel(maybe stopping execution too)

I think, that at least, because of termal and energy consuming reasons, GPU should not evaluate the statements after "discard", but some people on internet say that GPU computes the statements anyways. What I am more worried about, are the texture fetches after discard/clip.

(what if after discard, I have an expensive branch decision that makes the approved cheap branch neighbor pixels stall for nothing? this is crazy)
• By NikiTo
I have a problem. My shaders are huge, in the meaning that they have lot of code inside. Many of my pixels should be completely discarded. I could use in the very beginning of the shader a comparison and discard, But as far as I understand, discard statement does not save workload at all, as it has to stale until the long huge neighbor shaders complete.
Initially I wanted to use stencil to discard pixels before the execution flow enters the shader. Even before the GPU distributes/allocates resources for this shader, avoiding stale of pixel shaders execution flow, because initially I assumed that Depth/Stencil discards pixels before the pixel shader, but I see now that it happens inside the very last Output Merger state. It seems extremely inefficient to render that way a little mirror in a scene with big viewport. Why they've put the stencil test in the output merger anyway? Handling of Stencil is so limited compared to other resources. Does people use Stencil functionality at all for games, or they prefer discard/clip?

Will GPU stale the pixel if I issue a discard in the very beginning of the pixel shader, or GPU will already start using the freed up resources to render another pixel?!?!

• By Axiverse
I'm wondering when upload buffers are copied into the GPU. Basically I want to pool buffers and want to know when I can reuse and write new data into the buffers.

# DX12 error using resource barrier from multiple commandlists for same resource

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In dx12 we have to manage resource before/after state ourselves, but all the dx12 docs sample code uses the same commandlist to call resourcebarrier. in my program, I use a computeCommandList to update a volume buffer and then use graphicCommandList to visualize the volume every frame. So for the volume buffer resource state I have the following state change flow:

void CreateResource(...){
...
m_graphicCmdList->ResourceBarrier( 1, &CD3DX12_RESOURCE_BARRIER::Transition( m_volumeBuffer.Get(),
D3D12_RESOURCE_STATE_COPY_DEST,
VRET( m_graphicCmdList->Close() );
ID3D12CommandList* ppCommandLists[] = { m_graphicCmdList.Get() };
m_graphicCmdQueue->ExecuteCommandLists( _countof( ppCommandLists), ppCommandLists);
...
}
void Update(...){
...
!! m_computeCmdList->ResourceBarrier( 1, &CD3DX12_RESOURCE_BARRIER::Transition( m_volumeBuffer.Get(),
D3D12_RESOURCE_STATE_UNORDERED_ACCESS ) );
...
m_computeCmdList->Dispatch(...);
...
m_computeCmdList->ResourceBarrier( 1, &CD3DX12_RESOURCE_BARRIER::Transition( m_volumeBuffer.Get(),
D3D12_RESOURCE_STATE_UNORDERED_ACCESS,
...
}



However I got error msg @ !! line:
D3D12 ERROR: ID3D12CommandList::ResourceBarrier: D3D12_RESOURCE_STATES has invalid flags for compute command list. [ RESOURCE_MANIPULATION ERROR #537: RESOURCE_BARRIER_INVALID_COMMAND_LIST_TYPE]

Any idea? Thanks

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As I understand it, the different command list types (graphics/direct, compute, and copy) can only deal with resource states that they can understand. So In order to transition to or from a pixel shader resource, you need to use a graphics command list. So you'll need to transition to and from the UAV state on your graphics command list, rather than on your compute command list.

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As I understand it, the different command list types (graphics/direct, compute, and copy) can only deal with resource states that they can understand. So In order to transition to or from a pixel shader resource, you need to use a graphics command list. So you'll need to transition to and from the UAV state on your graphics command list, rather than on your compute command list.

Thanks, but the dx12 doc doesn't mention anything that different command list types have this kind of restrictions.... sign....

However it did mention that

"The debug layer normally issues errors where runtime validation fails:

• If a subresource transition in a command list is inconsistent with previous transitions in the same command list.

"

So I guess maybe in my case from m_compoutCmdList point of view, the first call to ResourceBarrier have before state not matching the previous transition in this commandlist (since the initial resource state set is in m_graphicsCommandLIst)?

And if that is the case, it will be a headache to sync resource state for multiple commandlist if we want to use multiple commandlist to call resourcebarrier?