• Advertisement
  • Popular Tags

  • Popular Now

  • Advertisement
  • Similar Content

    • By Jason Smith
      While working on a project using D3D12 I was getting an exception being thrown while trying to get a D3D12_CPU_DESCRIPTOR_HANDLE. The project is using plain C so it uses the COBJMACROS. The following application replicates the problem happening in the project.
      #define COBJMACROS #pragma warning(push, 3) #include <Windows.h> #include <d3d12.h> #include <dxgi1_4.h> #pragma warning(pop) IDXGIFactory4 *factory; ID3D12Device *device; ID3D12DescriptorHeap *rtv_heap; int WINAPI wWinMain(HINSTANCE hinst, HINSTANCE pinst, PWSTR cline, int cshow) { (hinst), (pinst), (cline), (cshow); HRESULT hr = CreateDXGIFactory1(&IID_IDXGIFactory4, (void **)&factory); hr = D3D12CreateDevice(0, D3D_FEATURE_LEVEL_11_0, &IID_ID3D12Device, &device); D3D12_DESCRIPTOR_HEAP_DESC desc; desc.NumDescriptors = 1; desc.Type = D3D12_DESCRIPTOR_HEAP_TYPE_RTV; desc.Flags = D3D12_DESCRIPTOR_HEAP_FLAG_NONE; desc.NodeMask = 0; hr = ID3D12Device_CreateDescriptorHeap(device, &desc, &IID_ID3D12DescriptorHeap, (void **)&rtv_heap); D3D12_CPU_DESCRIPTOR_HANDLE rtv = ID3D12DescriptorHeap_GetCPUDescriptorHandleForHeapStart(rtv_heap); (rtv); } The call to ID3D12DescriptorHeap_GetCPUDescriptorHandleForHeapStart throws an exception. Stepping into the disassembly for ID3D12DescriptorHeap_GetCPUDescriptorHandleForHeapStart show that the error occurs on the instruction
      mov  qword ptr [rdx],rax
      which seems odd since rdx doesn't appear to be used. Any help would be greatly appreciated. Thank you.
       
    • 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? 
    • By turanszkij
      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.
      clip: Discards 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?!?!



       
  • Advertisement
  • Advertisement
Sign in to follow this  

DX12 vulkan barrier initial state confusion

Recommended Posts

hi!

vkCmdPipelineBarrier needs srcStageMask and srcAccessMask, what should be the initial value for these parameters right after a resource is created? In DirectX 12, you can specify initial state for resources, what about vulkan?

Share this post


Link to post
Share on other sites
Advertisement

you can also provide an initial state (member of VkImageCreateInfo) but it has to be VK_IMAGE_LAYOUT_UNDEFINED or VK_IMAGE_LAYOUT_PREINITIALIZED.

Share this post


Link to post
Share on other sites
The pipeline stage doesn't have anything to do with resource initial state. Pipeline barrier allows to change for example image layout but it's up to you to decide how and when you are going to use the resource. For example, a newly created image with bound memory must make sure that all the writes and reads already happened before you try to change the layout. The safest place ( but usually least optimal )  is going to be a top of the pipeline for both - source and destination stages, as you may want to use this resource for example as sampled image. But again it depends on when and how you use your resource in the pipeline. To understand barriers you may think of it as "all the access operation must complete before source stage(s) to perform access operations after destination stage(s)". If we continue the example of image layout transition, usually the source stage for the new image is top of the pipeline ( regardless if the old layout is preinitialized or undefined ). The source access usually stays empty for uninitialized layout ( the data is undefined, no read and writes will occur at this point ). If your image is preinitialized you are going probably to write the data, so host write access must be complete before layout transition will happen. Those layouts are useless anywhere in the pipeline, so we use top of the pipeline as the source stage. Now depends on what you want to do next. If for example, you want to turn your image into the color attachment, then your destination stage mask will include color attachment output bit and access mask will include color attachment read and write bits. However, if you want to sample image in the shader, you need to perform transition earlier ( for example your new layout is VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL ). The stage mask should include all stages that may try to sample your image ( so mostly all shading stages ). Destination access flag would include shader read bit as that's the only operation that may happen after layout change.
 
I'm not sure if it's clear enough. I used image resource as the example although mind that barriers are a lot more complex in terms of what and how they synchronise. The example above is a simplification of the concept to help you understand what stages and access masks are.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Advertisement