Large scene approach

[Noyd]

Hi
Im working on a large area (hotel lobby), deadline on wensday so
got some urging questions. First is,

1.My rendertimes now are crazy, takes about a whole night for shot. Is
theres a way to cut down on the rendertime, without to much loss on quality?
Im willing to compromisse some quality for faster renders. My settings now are
from all Michas advise, some im not totally wrong

2. I cant use an HDRI as picturefram bakground, since that takes to much
of my cpu, how do i get the most out of a jpg pic background?

3. Im working on a day scene, but i wonder if theres an easy way to make it a night scene?
Does it work just turning GI down, and make all the lightbolbs in the seen emissive and intense?

[tommymartel]

Re: Large scene approach

i dunno much for questions 2 and 3 but for the render time maybe try to reduce the quantity of lights in your model, worked for me in some situations.....

do you have many lights in it ?

[Micha_cg]

Re: Large scene approach

1. For max speed I would use:

* IM + LC (IM max rate at -1 or lower (-2 ..) for high res .... if the IM pass is slow)

* don't use many lights

* try to use rectangular lights instead spots/points and enable "store with IM"

* if you can, best avoid lights and use emitters instead (but emitters are bad for small high intensity "lights")
You can use hundred of emitters at your scene, but not hundred of lights.

2. I never have seen that a textured emitter (in this case based on a picture frame) cause longer render times.

3. I would try this too. I think, it's good to use an evening sky HDRI (general blueish tint) at low intensity and enable interior lights everywhere. It could be good to use a light color contrast for interior/exterior, warm/cold.

[Noyd]

Re: Large scene approach

Hi thanks for all the tips.
I acctually have no lights at all, but many windows and some lights hanging
off the ceiling with emissive material, its still really slow but im trying out IM+LC right
as we speak.
Ill try the evening sky and se what happends. Ill update later on the day with examples, and times!

[Noyd]

Re: Large scene approach

Ok, im rendering right now and using the IM+LC on -3, and its still to slow. I got about 10 renders to do in 48 hours :'(. I need to compromisse the quality even more. And do some photoshop work instead. Wich parameters should i mess around with for the
low quality, fast speed vs high qaulity, low speed ratio? here is my settings.

[jrharvey]

Re: Large scene approach

1. For max speed I would use:

* IM + LC (IM max rate at -1 or lower (-2 ..) for high res .... if the IM pass is slow)

* don't use many lights

* try to use rectangular lights instead spots/points and enable "store with IM"

* if you can, best avoid lights and use emitters instead (but emitters are bad for small high intensity "lights")
You can use hundred of emitters at your scene, but not hundred of lights.

2. I never have seen that a textured emitter (in this case based on a picture frame) cause longer render times.

3. I would try this too. I think, it's good to use an evening sky HDRI (general blueish tint) at low intensity and enable interior lights everywhere. It could be good to use a light color contrast for interior/exterior, warm/cold.

I think your right about the emisive material. I had a scene with probable 100 lights and I used an emisive material instead of point/rectangular/spot light and it only took maybe 15-20 minutes per render where it would have taken MUCH longer if I had used real lights. Of course I had to bump up the multiplier to an ungodly level to get it to act as an actual light but it worked great.

[dalomar_cg]

Re: Large scene approach

Emissive materials are not effective for lighting spaces. They may be "faster" because they don't require having direct light traced, but they don't light the space in the same way and can cause artifacts.

What I would consider a better alternative is to have rectangular lights, reduce the number of subdivisions (8 is too high...in situations where there are a ton of lights you could get away with 2), make sure Store with IM is enabled, and adjust the cutoff on the lights. The cut off is rather important because that can prevent a number of rays being cast just by knowing the distance from a given light. In cases were there are a large number of lights, the cut off won't be nearly as visible and you can actually set it a bit higher than normal which also helps.

[Noyd]

Re: Large scene approach

Ill cut down the subdivisions, and try that.. right now im not even halfway throug the scene and it taken 3 hours. I put the noise threshold way up in hope that i would help but i didnt..
any advise on tweaking to get the fastest, and yet presentable renders. Fast being the priority right now

[Noyd]

Re: Large scene approach

i tweaked my settings and its working, i alss found i had hidden lights on :
A bunh of emessive materials now will do the trick! How do you recommend the settings for the emessive should be to light the scene up?

[Micha_cg]

Re: Large scene approach

i tweaked my settings and its working, i alss found i had hidden lights on :
A bunh of emessive materials now will do the trick! How do you recommend the settings for the emessive should be to light the scene up?

I do it per trial and error. It depends on the scene, are lights direct visible or not, ...

[tommymartel]

Re: Large scene approach

i see that your LC subdivs setting are at 1000, maybe try 600 or 800, and see if the quality of the render is ok with you...?

[Micha_cg]

Re: Large scene approach

If I try to optimize a rendering, than I look, which part of the calculation is slow. If the LC need a long time, than I try to find a solution- less lights, more emitters or less LC subdivs. If the IM is slow, than I try a lower max rate or less IM subdivs. If the final pass is slow, than reflections/refractions could be the reason or duplicated objects or ...

[Noyd]

Re: Large scene approach

Yes, the render stage, is the problem, thats the part that takes all night.. ill have to make some adjustments to that. I hope to have a picture soon to show, im waiting it out. I guess its all the refraction reflection, i have alot of glass and reflective material, wich parameter should i adjust to make the particular process faster?

[Micha_cg]

Re: Large scene approach

refraction reflection ... I hope once a day we will get the interpolation options:

http://www.spot3d.com/vray/help/150S...ial_params.htm

http://www.spot3d.com/vray/help/150S...reflect_interp

For now only strong hardware helps.

[Noyd]

Re: Large scene approach

I read about that, would be great if there was that option.

The problem is, duplicated objects. I got tons of em. Im doing a hotel lobby
and have many many furnitures and lights copied all over the scene. Could
that be it? what can i do about it since i need them all for the interior renderings.