Light Cache animation time issues

[JeremyRamsay]

Hi, I'm trying to calculate the light cache for a 300frm animation. Nothing exciting in the scene, just a pretty simple interior. See pics included. I'm using the method Light cache for both Primary and Secondary bounce, set to Fly By mode, then calculating the Irradiance map separately. Light cache subdivisions set to 5000. Scale set to World. Sample size 100mm. I've used this method many times but on this particular project the Light cache was still calculating after 2.5 days. Is anyone aware of this happening for whatever reason. Many thanks chaps.

[Devin Johnston]

It's unusual to use LC for both primary and secondary, why aren't you using IR?

[JeremyRamsay]

The technique I use was developed by Brian Smith off a Vismasters DVD, Training for Architectural Visualization, definitely worth a look if you can still find it. In it, it's advised to select the LC for both Prim and Secondary. Once the LC is calculated, you then calculate the Irrad map. Both maps are set to Fly By mode. I don't fully understand the workflow but it's a technique that, (normally), works, though I'm aware there's different ways of producing the two maps needed.

[Devin Johnston]

I'd say your speed issue is directly related to this method, I think the subdivisions are way to high I usually set mine to 1000 or less for an animation. Have you tried using LC as your primary, I believe this would be much faster and give you a cleaner GI solution, your screen shots showed a lot of GI noise.

[JeremyRamsay]

I am using LC as the primary? Do you mean not to use it for the secondary as well? The LC does render at 1000, I know that already as I've tested it but I thought it wouldn't be enough to carry through the animation. If you think it'll work I'll give it a go though, thanks. The screen shots were rendered at very low settings. Let you know what happens.

[Devin Johnston]

Sorry I ment IR as your primary and LC as your secondary.

[Francisco Penaloza]

I know the tutorial that you are talking about, but I have done several animation just pre-calculating Irr Map as multiframe incremental and Light Cache Fly-through at the same time. Light Cache it is always calculated before Irrandiance map any way, that old tutorial work flow can be adapted

 

Now I also setup my Light cache lower, 2000 or 2500 when it is a very complex situation, but most of the time 1500 work just fine.

 

With all this said, I never setup very long cameras movements, That old school of flying around the building and keep a constant movement until the last bathroom in your building is way gone.

Try to setup short cameras movements this will help you with your light calculation too, maybe that's why you need such high Light Cache values, 5000 IMHO is way overkill. Even if you are in the same room a 3 or 4 camera movements will be more pleasant visually than a rotating camera trying to show the whole room at once.

As a side note Displacement, fur and big scattered areas also affect Light cache calculations, in this case Brute force can be a better option, but in your case being an interior, I don't think this is the problem.

[JeremyRamsay]

Thought I'd already replied but obviously not, I'll give the above techniques a shot. I was originally just curious as to why my old technique worked so many times but stalled on this one. Right or wrong I've ramped up the LC to 10,000 sub divs in the past and haven't had issues. I suppose every model is different so Light cache calculation demands will be likewise but I'd love to know why after nearly 72 hrs the light cache was only half way calculated when there was nothing in the scene problematic as far as I can see. I've got a monster tech setup and tweaked all the materials as usual. On other points, yep, short cameras and slow movements are the way to go now. Thanks for the replies.

[RyderSK]

You might have set-up the LC so high it has problems being allocated inside Ram and swaps, you can check out Task Manager to see how is CPU doing, if it's not 99perc. continuously, then you have problem exactly here.

 

It doesn't matter if LC is primary or secondary, it will do the same.

 

The LC+LC ++ IR is pretty exotic technique, I see how it could give slight GI advance, but really, I would just drop it. I usually stay between 2000-3000 even for extreme detail, which is what I did in my animation. Most will be picked-up by IR anyway so there is no need to focus too much on LC at all.

 

LC is mostly GI and Resolution dependant, but if you compute it for more than hour for decently long shot (6-8seconds, fullHD res) than you have it very wrong.

 

Btw: "Scale set to World" This is almost never good idea. Like already someone adviced, plan out your shots so they don't fly for far too long inside space and then you don't need to use World scale. All this gives you are those artifacts everywhere and funky GI.

Edited October 31, 2013 by RyderSK

[JeremyRamsay]

That's interesting because I'm starting to think there is some kind of limiter in place while the LC is calculating. It's getting to about 80% after a couple of minutes then freezing no matter how long I leave it. This is just at 1200 sub divs. Just as a test I calculated the LC at 2000 sub divs for a still image and it worked fine so it seems this is just a problem when animating. As I've said though I'm puzzled as to why it was working on previous models at much higher sub divs calculation, that's the main reason for this post. Ta for the advice about 'Scale set to World'.