impossible rendering times on interior scene

[Lupaz]

Hi,

I'm trying with my first interior scene with vray, but it is taking a lot of time to render, even with qmc early termination amount =1.0 noise tresh=1.0 and min samples = 30.
With exterior scenes vray is really fast and great. This interior scene is taking up to 10 times more time than the more complete exterior scene.
Here is the .max file. I there's someone that kind, would you tell me what I'm doing wrong?

http://www.freewebs.com/lupaz/79.zip

It is driving me nuts!!
Thanks.

[tom schuelke]

Hi lupaz.

Well this is what happens on interiors !

vray looks at discreet points all over the scene to look if there is any light so far.

from theese points, going on, it traces rays in a hemisperic way into the scene, to look if from this point it can see areas of light. now if there´s much light, like in extereior scenes, it is easy, to see enough light, and not so much rays are needed to get a good lightsolution.

compared to this, when you are in interiors, you need very many rays, to find those smal areas with light. immagine a dark room with only a very strong laser that illuminatas only om cm² you have to trace thousends of rays to "see" from the discreet points, if this smal area is there.

because of this known and statistical problem, the programmers did devellope workarounds.

first: Radiosity. not a workaround, but usualy solves this problem, because the light gets calculated the other way round, comming from the lightsource. after the first bounce, about 60 to 70 percent of the light allready is distributed.

secound: photonmapping.
the computer shoots virtual photons coming from the lightsources, that bounce arround and leave light on the walls. this makes a very rough aproximation of light, but in the next step, the renderer doesnt have to trace so many rays, to see smal areas of light, because everything allready is lit .

this method also is in vray 1.09, it can boost your interiors up to 2 times !

third, lightmapping
this method is much easier to setup as photonmapping and comes with the new beta 1.475. it also can boost your scenes as photonmapping does, but is much easier to setup and also can see more sorts of light, all sorts of backroundlight, spots...
it also gets used for the secoundary bounces, and this method i used for your scene

just use the new beta, and you will see your renderings will become much faster.

[natty]

Good explanaition Tom..

I would delete your ies sun ... replace with a direct light ... your vray light, you need to tick store with irr map .. at the moment it is brute force rendering your shadows and that is a reason why its taking so long.

[Lupaz]

Tom: thank you for the explanation! But is bad news for me. I was expecting a magic solution , Because I have only 512 Mb ram , I think photonmaping is not an option (At least, that is what natty said one time). About the beta... Is it free to download?

Natty:

at the moment it is brute force rendering your shadows and that is a reason why its taking so long

Sorry, but I don't understand this.

Thanks.

[natty]

ok ...well basically you need to turn on in the light option store with irradiancs map... so select your light.. got to the modify tap in max ... there you will have the info about the light ...there you will see the tick box... also tick ....


See here

[percydaman]

i found his file pretty slow even after removing the ies light and even turning off area shadows for those target spots.

[natty]

he has opacity maps in there aswell .. which will make it slower

[percydaman]

oh didn't catch those

[tom schuelke]

Yes and he also uses reflections up to a depth of five which he could reduce.

also hes scene seems to depend on the old 1.09, and he doesnt use any photonmapping or lightmaping.

what he also could do, is changing the antialiasing algorithm, if he uses softshadows.

well sorry i dont have more time to test the scene.

but at last the whole vray is the next to a magic butten that ever existed i think.

jus go on learning, and yes when you have bought vray, you get the 1.45 for free. just go to your loginside and scroll down to the bottom. here you find the 1.475 free for download. And be assurred its much much better allready in beta stage .

tom

[Lupaz]

Natty: Ok, now I get it , I allways thought "smooth surface shadows" would make things slower.

Tom:

Yes and he also uses reflections up to a depth of five which he could reduce

Should I reduce reflect subdivs too? I never noticed any difference on render time when I did that (never tried that much to say so )

what he also could do, is changing the antialiasing algorithm, if he uses softshadows.

What do you recommend? Simple two level with default settings is too slow either.


Thanks!!

[tom schuelke]

Hi Lupaz this is something i wrote somewhere else for the antialiasing

Well


if you use glossys and also softshadows, the antialiasing algorithm you use is defniteley wrong.

adaptive subd. is ment for very clean scenes, only hard shadows or shadowmappiing, now displacement, and also no glossy reflections.

if your scene is that way, this algorith by far is the fastest.

it analyses the edges of your objects and this way has to render much less in the areas where nothing happens. This is the analythical method.

glossys, softshadows and also displacement are pixelbased things. wherever you have such pixelbased effects, the analythical method of the adaptive subdivision algorithm try´s to analyse on every pixel because he dont know if it is an edge or not. (an edge could be reflected !), and so he analyses itself to death .

the method of choise now should be simple two level, that uses a way of undersampling for the antialiasing. this can save you half or a third of your rendertime depending of how many glossys, softshadows and displacement. We had a big scene with many many details, and softshadows, and after switching to simple twoo level, we came from 22 minutes to 8 minutes.

fixed rate, well is good for example when you use 1.457, and use the new vray framebuffer. when you use interactive exposuercontrol whith real rgb, simple two level wouldnt have set enough antialiasing samples in very bright areas. (this algorithm also takes this into account ), and when you turn down brightness, you soon would notice that while details get into those bright areas (as in hdri), there had been not enough antialiasing samples. in this only case and the case of excessive details, softshadows and also displacement, fixed rate could make sense and also get the fastest.

hope this helps a bit.

Tom

so try also the simple two level. i´ve seen you use many softshadows in your spots if i am not wrong. so try this secound method.

ah and yes i rendered your scene with allmost your settings, but together with lightmap for secoundary bounces, and qmc a bit improved. i removed ies sunlight, and made the vray light shadow get rendered into the lightmap.


here it is. you could post an image with rendertime also to see if it is better.

also something with the geometry on top seems to be wrong. but i had no time to analyse furthermore.

Tom

[Lupaz]

2,14 minutes!!!!!!!!!

Mine takes at least an hour in 640x480!! I got to have that lightmap thing!!

Thanks Tom

[natty]

Ok i had time to have a proper look .... i changed all your mats to a single white vray mat to illiminate any problems, turn clipping off for your camera ... which was creating some bad stuff on the ceiling, deleted all your lights and replaced them with 4 vray lights and 1 direct ... and rendered with lightmap .. and nothing else....






Regards

[tom schuelke]

Hi natty

Dont mak him jump out of the window.

Hi lupaz. Its worth going on isnt it

Tom

[natty]

...sorry .... hehehe.... Lets face it ,,there is no other renderer that can render an internal shot so damn fast ... and i can cut that time in half..