They restarted 3ds Max. Reset the scene. Tried "Morning." Same thing. The dome light stayed stubbornly black.
The fix? Change the to a simple path like C:\VRayTemp (no spaces). Or, in newer versions, update to the latest hotfix.
Twenty minutes later, after sweating through the fix, Alex had a beautiful golden sunset. They delivered on time. But they never forgot: check the damn path spaces.
They Googled furiously: "vray light gen not working" — and found forum threads from 2018, vague mentions of "paths," and a buried comment about "Windows usernames with spaces." vray light gen not working
V-Ray Light Gen, in some versions, fails to write temporary HDRI preview files to a path containing a space. It silently fails. No error. Just a dead, dark dome.
Alex’s Windows username was — with a space.
This is a frustrating moment for any 3D artist. Let me tell you a short, relatable story about this exact problem, then give you the most likely fix. They restarted 3ds Max
The little progress bar appeared... crawled to 100%... and then… nothing. The Light Gen window went blank. The dome light in the viewport was still dark. No textures. No preview. Just silence.
Alex thought, "No problem. I'll use V-Ray Light Gen. Click a preset. Done."
Panic.
It was 2 AM. Alex had a villa exterior due in 12 hours. The client wanted "dramatic, cinematic sunset lighting."
That was it.
They selected the dome, chose "Sunset," and hit . The dome light stayed stubbornly black