I am experiencing some black blocks appearing across the screen while playing rimworld, seems more often when using higher game speeds but not sure.
I have not seen any artifacting in other games and have run Furmark for 20+ mins without any noticeable glitches so i don't think its a hardware issue.
Display device is a gtx 780ti.
Mods?
Please can you post your log file (as an attachment), as well as confirming whether or not you are using any mods. Details on where to find you log file can be found in the pinned "How to Report a Bug" thread at the top of the bugs forum.