use lightcache for glossy rays..slower?

[super gnu]

in my scenes i usually use this option.

however im stuck with a scene now where if i have it on, my displaced stone floor, with soft glossies, takes -way- longer to render with it enabled than without. as in 45 mins instead of 5 or 6... conversely, another part of my scene takes forever to render - unless- i have it enabled.. so im a bit stuck.

any suggestions?

[Morne]

is this overall or just the actual rendeinrg part?
is the lc calculation slower/faster with it on/off?

[super gnu]

just the actual rendering, didnt notice a difference in the calc times

[vlado]

What are your light cache settings?

Best regards,
Vlado

[super gnu]

well in this case its a long flythrough lightcache.. its a 900 frame shot that goes through a lot of landscape. i used 10,000 subdivs due to this.. everything else on default. i also tried one with only 1500 subdivs but it still took longer with " use lightcache" on..

i understand that its advised to use "world space" when doing flythroughs, but since part of my scene looks over a 50 sq km forest, i think it might get a bit bogged down unless the samples were massive. so i kept it at screen space.. worked fine for me in the past.

i tunrned off "retrace threshold" as i didnt notive any visual improvement with it on, and it slowed things down further..

to be honest ive notived something else in my scene that was causing me headaches.. i have a moving vehicle with the "use imap" off trick to get perframe gi. i was pulling my hair out as in most of my tests the rendertime was around 1 hr a frame, but sometimes, usually as i prepared to do the final render, it jumped to over 5 hrs a frame.. mostly spent on the vehicle.

turns out since i was using a very subtle 3dsmax fog in the scene (which i kept turned off during imap calcs since it added splotches.. seems to generate gi) and didnt connect mentally that since the car has perframe gi, when i had the fog on, it was (i guess) going crazy doing extra samples on the vehicle. luckily the fog was a little extra tweak and very easy to do in post.

i have no idea if this could be related to the "use lightcache for glossy rays" thing.. i would have to do some more test renders..

[vlado]

You might also reduce the number of interpolation samples for the light cache; the default is 10, but you can use for example 5. I would also love to take a look at your scene and see if it is possible to optimize it.

Best regards,
Vlado

[super gnu]

well the scene is absolutely massive, a few gigabytes of data even rarred, but ill happily send it if you want to fiddle.. its a personal project so no issues there. you have an ftp i can log on to?

[Zdravko]

Please send us an e-mail to support@chaosgorup.com so we could provide you with an FTP account.