don’t know if this helps, from dev TextFAMGUY1
We removed a crapload of old shaders from the game with this update, for optimisation and performance reasons. It’s likely that your Hammer is trying to load at a Direct X level below 9, or at Shader Model 2.0, which causes it to have many display issues as we removed those shaders. I would know as I had this exact same problem when the old stuff was stripped out.
Luckily, there is a fix. When this happened to me, it was because my laptop was making Hammer run from the integrated graphics rather than my graphics card. So I used the Nvidia Control Panel to tell it to use the graphics card, and voila! Fixed! So, try and make sure your computer isn’t forcing Hammer to use integrated graphics, that is likely the issue.
https://steamcommunity.com/app/362890/discussions/0/364041776188597284/?ctp=3