Other ideas for optimising this scene . . .

[Matt]

Hi

I'm rendering a scene at the moment (shown below) that is taking an extraordinary length of time. It's of a medium complexity:

It has 231 lights, 14 of which are area lights (quality 5) the rest point and distant.

Total polycount isn't anything high.

No radiosity, hypervoxels, caustics, refraction are being used.

Antialiasing is set to Enhanced Low.

Ray recursion has been set to 6, only surfaces that _have_ to be reflective have been set to reflect.

The glass surfaces that are only ever viewed from one side have been reduced to one-sided polygons (i.e. no thickness)

It has to be of a reasonable size, it will be used for print, not magazine quality but higher than a normal render.

- - - -

Apart from the lowering the area light quality to 4 and AA to low, does anyone have any tips that could help optimise the scene?

I don't have much time to render, and although I will be using a render farm for this job I need to make sure it will finish in the time we have left.

There will be three scenes, each with three views (print res).

Any help would be appreciated!

Cheers
Matt

[ingo]

Thats simple, throw away the area lights and some of the others. I guess you can get a similar lighting with around 30 to 50 lights.

Just curious, how much is the rendertime ?

[toby]

Turn off shadows for the point lights (are they on?)

With no Ray-trace refraction, Ray-recursion of 2 should be enough, you don't really need to see the reflection of the walls in the reflection of the pillars in the reflection of the walls!

I'm guessing you could get by without area lights too -

[Matt]

Thanks for the replies.

Just over 24 hours for an 800x600 test!!!!

All the points lights have shadows turned off. I need that many because I need the lights (along the edge of the platform) to throw some light, just having glow isn't enough.

I need the area lights for _some_ soft shadowing, hard edged shadows look naff unless it's bright outdoor sunlight, which this clearly ain't.

Ray recursion limit - I know about counting reflective surfaces in the scene, but how does it go again exactly? If it was set to 1, would every reflective surface in the scene reflect everything once? Or would only 1 of the reflective surfaces be calculated?

[toby]

Originally posted by Matt
Just over 24 hours for an 800x600 test!!!!

aaaacckkk! what are you using, Mac VX 68040 render nodes?? :p

Something must be wrong here, I once rendered HV in a reflective tube, recursion at 16 on a G3 300 and it took an hour at 640x480. The same scene on a dual 450 was 20 min. - ??? No area lights though, that must be the killer.

How about shadow maps or the spinning-light-trick for soft shadows?

Ray-recursion is how many ray bounces you get, but 1 seems to get no reflection, 2 gets you 1 ref.

[Matt]

Sorry, no, I meant about 12 hours! :rolleyes:

I've dropped the ray recursion limit down to 3 which is the minimum I can go before it starts to look too fake, but that's half what I thought it needed to be which is a good start! :)

I've also dropped enhanced AA in favour of low AA, but I lowered the adaptive sampling threshold down to 0.03, instead of 0.1 which helps up the quality a little without having to go to enhanced.

I really hope AA is speeded up in v8, I've had renders where the AA process takes longer than the actual rendering!!!

Also dropped the quality of the area lights to 4.

Hopefully that will all add up to reasonable times rather than silly times!!!

I _could_ replace the area lights with shadow mapped spots, but until they are improved (deep shadows map would be awesome!) I need the quality of shadows area lights give you.

[Matt]

Oh, test renders are done on my Dual 2Ghz Xeon / 1GB RAM.

I have access to the following machines in the office (other peoples PCs):

Xeon:
Single 2.0 GHZ / 1GB RAM
Single 2.6 GHZ / 1GB RAM
Dual 2.0 GHZ / 1GB RAM
Dual 2.6 GHZ / 1GB RAM
Dual 2.6 GHZ / 1GB RAM

Pentium:
Dual 3.0 GHZ / 1GB RAM

but the renders need to be finished overnight, for 9 print renders to be done is asking a little too much!

[Stewpot]

Hi Matt,

I would guess the biggest killer are the area lights and the reflections.

Could you reduce the number of area lights but increase the size of the ones you leave to cover the ones you remove. And would this make a difference, since you can size area lights as I remember, and get more coverage.

Hope this helps.

[Matt]

I did think of that, but the only problem with area lights when scaled is the graininess, I'd then have to bump up the AA to compensate!!

I just can't wait for the next big renderer update, hopefully speed will be addressed. I won't hold my breath for v8 to have anything major done to the renderer, but never say never eh!

[Elmar Moelzer]

Hey Matt!
Cool scene!
That many lights are going to kill every renderer.
I see you problem though and why you need them.
I would suggest trying the following things:
1. No matter whether it takes longer to render, but you should never, never use Adaptive sampling especially not if you are going for print- res.
2. With AS turned off you can lower the area- light- quality to 4 or 3 and still get good restults (also try using shading- noise- reduction).
3. This might again lower render- times enough to letting you use a higher AA- level.
4. If you can use higher AA you might consider using fewer, but spinning area- lights with motion- blur and a level of 2 (yes this works pretty well).
5. Try reducing the amount of point- lights by using a single or a few linear lights with raytraced shadows on instead.
It might render indeed faster as area and linear lights are not as slow as one might think (they are slow, but not that slow).
6. Are you using reflection- blurring?
If so, try the imagefilter, it is much faster, or use (this is what I usually do) a micro- bump- map.
7. Apply a gradient to the reflection that is based on incidence- angle to lower the reflections on the floor close to the camera (this wont help with rendertimes, but it would make the scene look more realistic).
If everything turns out well you can reduce the rendertime while increasing image- quality at the same time.
Hope that helps
CU
Elmar

[Matt]

Thanks Elmar, some good tips there! :)

I just realised that I turned off every other area light! There are in fact only 6 area lights equally spaced down the platform.

I'll give your idea of trying AA without adaptive sampling and lower area light quality.

I can't use 'Shading Noise Reduction' because the scenes will be split rendered, I gather this causes havok with SNR.

Last time I tried linear lights I found them to be so slow that they were almost unusable! Besides to avoid the 'dark edges' of area lights they are placed outside the platform, the roof is a seperate layer and is told non to cast shadows.

It's the only way I've found of having soft shadows in an interior setting without having to use GI, it's a real pain!

Reflection blurring is off, the floor has a micro-bump on it (mainly because it looks like it does in real life, from the photos anyway)

I _always_ use gradient-incidence angles for my reflections! :)

Cheers
Matt

[Elmar Moelzer]

Hey Matt !
If you are not using Adaptive Sampling you can just as well turn on motionblur and rotate or move your area- lights and use fewer of them. Motionblur wont take any longer to render.
CU
Elmar

[A Mejias]

Some great tips! For noise reduction check out the post on NeatImage in this forum.