• Advertisement
  • Popular Tags

  • Popular Now

  • Advertisement
  • Similar Content

    • By mark_braga
      I have a pretty good experience with multi gpu programming in D3D12. Now looking at Vulkan, although there are a few similarities, I cannot wrap my head around a few things due to the extremely sparse documentation (typical Khronos...)
      In D3D12 -> You create a resource on GPU0 that is visible to GPU1 by setting the VisibleNodeMask to (00000011 where last two bits set means its visible to GPU0 and GPU1)
      In Vulkan - I can see there is the VkBindImageMemoryDeviceGroupInfoKHR struct which you add to the pNext chain of VkBindImageMemoryInfoKHR and then call vkBindImageMemory2KHR. You also set the device indices which I assume is the same as the VisibleNodeMask except instead of a mask it is an array of indices. Till now it's fine.
      Let's look at a typical SFR scenario:  Render left eye using GPU0 and right eye using GPU1
      You have two textures. pTextureLeft is exclusive to GPU0 and pTextureRight is created on GPU1 but is visible to GPU0 so it can be sampled from GPU0 when we want to draw it to the swapchain. This is in the D3D12 world. How do I map this in Vulkan? Do I just set the device indices for pTextureRight as { 0, 1 }
      Now comes the command buffer submission part that is even more confusing.
      There is the struct VkDeviceGroupCommandBufferBeginInfoKHR. It accepts a device mask which I understand is similar to creating a command list with a certain NodeMask in D3D12.
      So for GPU1 -> Since I am only rendering to the pTextureRight, I need to set the device mask as 2? (00000010)
      For GPU0 -> Since I only render to pTextureLeft and finally sample pTextureLeft and pTextureRight to render to the swap chain, I need to set the device mask as 1? (00000001)
      The same applies to VkDeviceGroupSubmitInfoKHR?
      Now the fun part is it does not work  . Both command buffers render to the textures correctly. I verified this by reading back the textures and storing as png. The left texture is sampled correctly in the final composite pass. But I get a black in the area where the right texture should appear. Is there something that I am missing in this? Here is a code snippet too
      void Init() { RenderTargetInfo info = {}; info.pDeviceIndices = { 0, 0 }; CreateRenderTarget(&info, &pTextureLeft); // Need to share this on both GPUs info.pDeviceIndices = { 0, 1 }; CreateRenderTarget(&info, &pTextureRight); } void DrawEye(CommandBuffer* pCmd, uint32_t eye) { // Do the draw // Begin with device mask depending on eye pCmd->Open((1 << eye)); // If eye is 0, we need to do some extra work to composite pTextureRight and pTextureLeft if (eye == 0) { DrawTexture(0, 0, width * 0.5, height, pTextureLeft); DrawTexture(width * 0.5, 0, width * 0.5, height, pTextureRight); } // Submit to the correct GPU pQueue->Submit(pCmd, (1 << eye)); } void Draw() { DrawEye(pRightCmd, 1); DrawEye(pLeftCmd, 0); }  
    • By turanszkij
      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 Alexa Savchenko
      I publishing for manufacturing our ray tracing engines and products on graphics API (C++, Vulkan API, GLSL460, SPIR-V): https://github.com/world8th/satellite-oem
      For end users I have no more products or test products. Also, have one simple gltf viewer example (only source code).
      In 2016 year had idea for replacement of screen space reflections, but in 2018 we resolved to finally re-profile project as "basis of render engine". In Q3 of 2017 year finally merged to Vulkan API. 
    • By tanzanite7
      vkQueuePresentKHR is busy waiting - ie. wasting all the CPU cycles while waiting for vsync. Expected, sane, behavior would of course be akin to Sleep(0) till it can finish.
      Windows 7, GeForce GTX 660.
      Is this a common problem? Is there anything i can do to make it behave properly?
    • By mark_braga
      I am working on reusing as many command buffers as I can by pre-recording them at load time. This gives a significant boost on CPU although now I cannot get the GPU timestamps since there is no way to read back. I Map the readback buffer before and Unmap it after reading is done. Does this mean I need a persistently mapped readback buffer?
      void Init() { beginCmd(cmd); cmdBeginQuery(cmd); // Do a bunch of stuff cmdEndQuery(cmd); endCmd(cmd); } void Draw() { CommandBuffer* cmd = commands[frameIdx]; submit(cmd); } The begin and end query do exactly what the names say.
  • Advertisement
  • Advertisement
Sign in to follow this  

Vulkan Allow sloppiness in pipeline

This topic is 596 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts



I've been porting my Direct3D code to Vulkan for a while now, and I found a few things rather annoying with Vulkan. What I'm trying to do is to use a single pipeline (single vertex shader) to allow rendering both animated and non-animated objects. I use two vertex buffers, one for pos/uv/norm/tang attributes and one for per-vertex animation data. The problem is that, when I make the pipeline to match my shader (which expects the second buffer to fill in some bound attributes), it crashes the driver if I don't bind the second buffer. So I tried to bind the same first vertex shader twice (data is irrelevant since I'm telling the shader not to use it via a UBO). Binding a dummy buffer works, but turns out it is very expensive (when rendering 5k+ objects, I get 50%+ performance loss). Is making two pipelines my only option? Is there a way to make it a bit more sloppy and allow incomplete input? I'm no expert in those things - but it seems like Vulkan could really just ignore filling in the attributes, since it already knows the stride of the entire vertex.



Thanks and regards,

Hasan Al-Jawaheri


Share this post

Link to post
Share on other sites
The whole point of Vulkan and D3D12 is that they don't fix any of your errors, so your code must always be perfectly correct.
In older APIs, the runtime /driver will always fix up sloppy code to avoid crashing the GPU, but now that's your job.

Share this post

Link to post
Share on other sites

Is making two pipelines my only option?


I just know enough to agree building all those pipelines is annoying, but 2 things:


I think you can serialize them to disk somehow, so those billion lines of setup code don't need to be in your shipping product.

You can make utility code to shrink the ammont of setup code (but personally i've had not much success with this yet...)

Share this post

Link to post
Share on other sites
Sign in to follow this  

  • Advertisement