I would say to use Bagginsbill's GenIBL to create an IBL map for your scene, and render in Firefly using IBL rather than IDL.  However, BB's downloads seem to have vanished into the aether... :sad:

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The Wisdom of bagginsbill:

"Oh - the manual says that? I have never read the manual - this must be why."
“I could buy better software, but then I'd have to be an artist and what's the point of that?"
"The [R'osity Forum Search] 'Default' label should actually say 'Don't Find What I'm Looking For'".
bagginsbill's Free Stuff... https://web.archive.org/web/20201010171535/https://sites.google.com/site/bagginsbill/Home