From Vray4C4d Forum
Author: stefan
LC takes more or less unlimited passes, if you use only LC(prim+sec) with high sample count you get a maxwell like system ( takes long to clear up)
it is physical correct but can be adjust with sample size and sample count.
bigger samples get faster but less exact. smaller samples get more exact like BF but need many samples. it has very good controll quality vs speed in vray. you see instantly what the image l will look like.
BF-brute force is very exact too, has very high quality but has a ray depth controll, it alone also renders long, but not as long as LC-maxwell method. very easy to setup.
IRMap takes one “intelligent” pass, it is a very fast and very intelligent system approximating the light distribution. it has a very nice light feeling and distribution. it brings less detail as the physical correct approaches LC or BF.
there for the most intelligent way is to combine 2 of the above:
ir+BF: very fast, very high quality, fastest for outdoors normally, most easy setup. a bit harder to setup for indoors.
ir+LC: very fast, fastest for indoors in most cases, very high quality when using good lc setup. lc gives info also to IRmap, very good combination for many cases. high control quality-speed. you also see instantly what you will get. the LC speeds up the IRmap as it passes info from LC to IR.
BF+LC: very very high qualiy, a bit slower than first 2 methods, many pro-users use that. maxwell like quality but still faster and more controll.
very good also for object animation. only recommened for professional vray users that already have good controll over settings.
all other settings or combinations make no real sense.
beside you can as strat suggested of course only use a primary pass, specially for outdoors sometimes only IR as prim with no secondary pass is enough. this gives super speed and saves a lot of memory. also good for animation.
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