If I want to render a scene at 2048 X 1024 how low can I pre-render the Irradiance map and reuse it in the higher render? I haven’t been utilizing a saved Irradiance map when I think I can.
hehhee. its the irradiance map limbo…
how low can you go
how low can you go
how low can you go
hehehe
I just got through rendering IR/LC for a still at 800x600, and rendered the final image with the saved IR at 2k. It really depends on the scene, as
does most everything with Vray. 
IMAP
Hmmm… I’ll play around and see how low I can go :lol:
…you can go 1/4 of the final…
eg: final=6000x4000, imap calc@ 3000x2000
final=720x480, calc=360x240
unless my powers of math are failing me your numbers exhibit a reduction of 1/2 not 1/4
Semantics. Each dimension is 1/2, but the image actually is 1/4 the size. Count the pixels. 
And… I’m not sure why people still render a small image then reuse the IR map. Unless I’m misunderstanding something, lowering the IR setting acomplishes the same thing, but much more easily.
For instance, a 320x240 image with IR of -3/0 that looks good will have the exact same solution as a 640x480 set to -4/-1, or a 1280x960 at -5/-2, or a 2560x1920 at -6/-3.
If I’m wrong, somebody set me straight, but I could swear Vlado has said as much. Plus, it seems to work just ducky in practice…
True, half image resolution, quarter the pixels.
@CCS: Yes, you are correct sir. There is no reason to half your render size when you can just lower your IR min/max settings by 1. And I remember previous posts where Vlado has said as much.
I have also done render tests to confirm this, and the IR calc time for say a 640x480 at -3/0 is almost identical to a 1280x960 at -4/-1. And the quality looks identical as well.