You need to be in a biome where the trees will turn to frosted leaves, like a Snowy taiga, then it needs to snow, and the leaves need to turn frosted, then wait. Look around.
I can't upload it, but it'll happen in any world, any biome where leaves turn snowy/frosted
The resource pack I'm using is Kelly's Minecraft Vanilla RTX
here's a link to the download Kelly's RTX
pls fix
It's irradiance cache