Render goes auto-CPU

gooHero

I had 4.16 installed, I think, two days ago. It would render fine with the GPU. Then the day before yesterday I installed 4.20 Pro and tried to render; and it worked well and went straight for the GPU and the speed was okay. Then today it suddenly drops back to the CPU automatically, and I no longer get any information in the renderbox about VRAM usage or anything else. I thought maybe I exceeded my available VRAM, so I deleted half the items in the scene and tried again. CPU immediately. Then I updated my graphics card drivers to the latest unneeded game ready one from NVIDIA and tried again. CPU immediately. I switched scenes to one that didn't have that many assets and am rendering right now with the GPU; BUT still without VRAM usage information and CPU/GPU prompt in the renderbox.  The scene I couldn't render had 5 lights (of which 1 was a sundial) a furnished house and 2 characters in it... mind you I deleted almost all the furniture and tried again. Is it really the case that I can't even render that much with an RTX 3070 8Gb? while I have an i9 10900F it is still EXCRUTIATINGLY slow to render; and you can't really do anything while it renders. What the f is going on with this programme?

 

regards,

goo

 

Edit 1: Moved the two characters over to a new scene, which includes 4 lights, 2 environment props, a lot of items and other stuff. Now it renders on the GPU again. I just don't get this sometimes. Big [mysterious] mystery to me :-S