My colleague and I wrote a blog post on Dynamic Resolution Rendering with DX12, specifically it’s an implementation which uses DX12 Placed Resources for render target resizing instead of scaling the viewport.

You can read about it and find the github links here:
https://software.intel.com/en-us/articles/dynamic-resolution-rendering-update-for-microsoft-directx-12

My colleague and I wrote a paper on DRR+Checkerboard Rendering and released a full implementation in a fork of the DX12 Mini Engine.

You can read about it and find the github links here:
https://software.intel.com/en-us/articles/checkerboard-rendering-for-real-time-upscaling-on-intel-integrated-graphics-v-12