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• By khawk
LunarG has released new Vulkan SDKs for Windows, Linux, and macOS based on the 1.1.73 header. The new SDK includes:

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• By khawk
LunarG has released new Vulkan SDKs for Windows, Linux, and macOS based on the 1.1.73 header. The new SDK includes:

• 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); }

• 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.

• 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.

Vulkan Row pitch when copying from VkBuffer to VkImage

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I'm working through adding texturing to my program by following vulkan-tutorial.com and was wondering about row pitch. The tutorial states that images must obey the implementation's row pitch amount, which makes sense.

However, the question I'm running into is that I want to use a VkBuffer for staging rather than a separate staging VkImage. From what I can tell, the only way to get the needed row pitch is from the linear tiled staging image. I'm assuming the optimal tiling image will have a different row pitch, and I can't find anything stating either way.

Can I use the row pitch from the destination optimal tiling image, or do I not have to worry about the pitch it in this case?

Edited by CirdanValen

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Using a copy from a VkBuffer instead of from a linear texture is definitely the right track. Trying to use a linear texture for staging is an exercise in frustration because you run into the irritating limitations that apply to linear textures (like limited format/mipmap support).

You shouldn't have to worry about implementation specifics though. Section 18.4 contains pseudocode describing how it expects your texture data to be laid out in your VkBuffer prior to a call to vkCmdCopyBufferToImage.

Assuming you're not using a block compressed format, the spec says:

rowLength = region->bufferRowLength;
if (rowLength == 0)
rowLength = region->imageExtent.width;

imageHeight = region->bufferImageHeight;
if (imageHeight == 0)
imageHeight = region->imageExtent.height;

elementSize = <element size of the format of the src/dstImage>;

address of (x,y,z) = region->bufferOffset + (((z * imageHeight) + y) * rowLength + x) * elementSize;

where x,y,z range from (0,0,0) to region->imageExtent.{width,height,depth}.


There is no need to worry about implementation specifics for staging texture data, that's the driver's problem/responsibility.