irradiance map presets question

[cocolas]

Hi,
from what I gather the irradiance map presets are resolotion dependent and optimized for 640x480......
does that mean that if I wanna double or more the render size (say 1200 or 1600 wide) will I also have to double my irradiance map settings like HSph. subdis and Interp. samples?? what about the mi/max rate??


thanks,

Paul.

[flipside]

I always use irradiance map (first diffuse) + direct (secondary bounces)

If a render looks good on let's say 800*600 with irradiance to -3,0
(regarding GI solution I mean), and you then change the res to 1600*1200, you can decrease the irradiance settings to -4,-1. (so -1 if you double resolution).

Example: If you calculate irradiance map at -3,-0 for 800*600, this means the following:
prepass1: GI calculated for image with resolution 100*75 (=800/2/2/2 and 600/2/2/2)
prepass2: GI calculated for image with resolution 200*150, with the info it gathered from the first pass (=800/2/2 and 600/2/2)
prepass3: GI calculated for image with resolution 400*300, with the info it gathered from the second pass (=800/2 and 600/2)
prepass4: GI calculated for image with resolution 800*600, with the info it gathered from the third pass
Because each new pass uses the rougher info from it's previous pass, vray knows where the more important (detailed) areas are, and therefore doesn't need to calculate more samples in the less detailed (flat) areas.

So if you want the same irradiance map info for the image @ 1600*1200, use -4,-1:
prepass1: GI calculated for image with resolution 100*75 (=1600/2/2/2/2)
prepass2: GI calculated for image with resolution 200*150, with the info it gathered from the first pass
prepass3: GI calculated for image with resolution 400*300, with the info it gathered from the second pass
prepass4: GI calculated for image with resolution 800*600, with the info it gathered from the third pass

HSph subdivs is the same as the hemispherical rays of fr, they only need lower values in vray. 50 is good for almost anything, try lower first, and if there are too many artifacts, go higher. Interp samples defines how the GI info is merged into each other (the neighbouring samples). Higher values will tend to blur the solution, so it looks smooth but looses detail. Lower values will cause more splotches but better detail. So to get better quality, raise hsph and lower interp (but 50/20 is usually very good!

Another important one is clr thresh and nrm (leave dist to 0.1 always). Both 0.3 is good, lower values will cause long rendertimes. Higher values speeds up things, but you loose detail again.

also visit http://vray.info/
lots of info there about everything!

[DP]

we happily get away with 20 HSph subdivs and 60 samples for high res work, yes its less accurate, but its often sufficient on a textured model.

[cocolas]

thanks guys

paul.