brians

This has been possible in Karma since H20.0 via the “background LPE”

https://www.sidefx.com/forum/topic/81445/#post-421936 [www.sidefx.com]

https://www.sidefx.com/docs/houdini/render/lpe.html#custom-alpha-plane [www.sidefx.com]

EP nineteenma
Every time I hit render in Karma, I need to wait ~15–20 seconds of black screen
before seeing the first pixel.

This is via MPlay? Or does this happen in IPR (ie the viewport) too?
If only with MPlay try setting this envvar and let us know if the stall still happens.

KARMA_XPU_OPTIX_FAST_COMPILE_OVERRIDE=1

(please note the use of this envvar may reduce performance a little in mplay)

Try tweaking the variance-oracle settings (or disable it completely)