I'm looking into building a streaming system for mipped images. I'm referencing the DirectX sample for memory management here: https://github.com/Microsoft/DirectX-Graphics-Samples/tree/master/TechniqueDemos/D3D12MemoryManagement
I have a couple related questions to this.
I'm leaning towards also utilizing tiled resources for mips, mainly because it allows me to avoid invalidating my pre-cooked descriptor tables any time an image updates, since I would effectively have to create a new ID3D12Resource with more / fewer mip levels when a stream / trim event occurs, respectively. Has anyone had success using tiled resources or noticed any potential performance impact related to having the page table indirection?
Also, I noticed that tiled resource tier 1 doesn't support mip clamping. Are there workarounds (in the shader, for example), or limiting the mip level in cases where we don't have a mip resident? Or am I required to create a new view mapped to the resident subset. This would also require that I rebake my descriptor tables, which I would like to avoid.
My second question is how to handle the actual updates. I would like to utilize a copy queue to stream contents up to the GPU. I have a couple approaches here:
Create a device-local staging image and run my async copy job to upload to it. This happens in parallel with the current frame using the existing image. At the beginning of the next frame (on the graphics queue) I blit from the staging memory to the newly resident mip, and then use the full mip chain for rendering.
Utilize sub-resource transitions to put part of the image into an SRV state and the other part into a Copy Destination state. The async copy queue uploads to the more-detailed mip levels while the current frame renders using the SRV subresources. This approach seems a bit more complicated due to having to manage sub-resource transitions, but it avoids a copy in the process. My question here is whether I need to specify the D3D12_RESOURCE_FLAG_ALLOW_SIMULTANEOUS_ACCESS bit on my resource, even though the transitions and accesses are occurring between different sub-resources. If so, do you know what kind of performance repercussions I could expect from this? Would I still be able to store my images in BCn formats, for example?
What is the best practice when you want to draw a surface (for instance a triangle strip) with a uniform color?
At the moment I send vertices to the shader, where each vertice has both position and color information. Since all vertices for that triangle strip have the same color I thought I could reduce memory use by sending the color separate somehow. A vertex could then be represented by three floats instead of seven (xyz instead of xys + rgba).
Does it make sense? What's the best practice?
I'm trying to understand implicit state promotion for directx 12 as well as its intended use case. https://msdn.microsoft.com/en-us/library/windows/desktop/dn899226(v=vs.85).aspx#implicit_state_transitions
I'm attempting to utilize copy queues and finding that there's a lot of book-keeping I need to do to first "pre-transition" from my Graphics / Compute Read-Only state (P-SRV | NP-SRV) to Common, Common to Copy Dest, perform the copy on the copy command list, transition back to common, and then find another graphics command list to do the final Common -> (P-SRV | NP-SRV) again.
With state promotion, it would seem that I can 'nix the Common -> Copy Dest, Copy Dest -> Common bits on the copy queue easily enough, but I'm curious whether I could just keep all of my "read-only" buffers and images in the common state and effectively not perform any barriers at all.
This seems to be encouraged by the docs, but I'm not sure I fully understand the implications. Does this sound right?
I need to share heap between RTV and Stencil. I need to render to a texture and without copying it(only changing the barriers, etc) to be able to use that texture as stencil. without copying nothing around. But the creating of the placed resource fails. I think it could be because of the D3D12_RESOURCE_DESC has 8_UINT format, but D3D12_RESOURCE_FLAG_ALLOW_DEPTH_STENCIL enabled too, and MSDN says Stencil does not support that format. Is the format the problem? And if the format is the problem, what format I have to use?
For the texture of that resource I have the flags like: "D3D12_RESOURCE_FLAG_ALLOW_RENDER_TARGET | D3D12_RESOURCE_FLAG_ALLOW_DEPTH_STENCIL" and it fails, but when I remove the allow-stencil flag, it works.