Very Slow Render Time

[berliner]

Hi Guys,

So I'm at the point in the project where everything looks the way I want it to.

I'm using a combo of FG/GI for this exterior scene (GI really helped)

The final format will be A4 size. so 3507 x 2480- per the clients wish. Which is pretty huge and requires a lot of horsepower for my laptop. I've started a test render to see how long it would take and after 2 hours, it had only rendered out like 11%!

It just started getting slower recently, maybe I OVER-test rendered

There are also 4 planes surrounding the bldg that are used for the reflections in the windows (and no, they don't inherit visibility and not visible to camera) which these also help in focusing photons as I've noticed.

Based on my settings, do you think there's something I should change, or that I'm doing wrong?

I saved an FG map and reused that, as well as enabled Geometry Caching.

I also hit the Conserve Memory and put it up to 1500...

 

Or is this simply how it's gonna go...several hours per each render?

[Justin Hunt]

try

 

Scanline OFF

Max reflections 2

FG rays per sample 80

Photons Max photons per sample 800

Trace Depth Max 30

Average GI 80000

 

Is your sun's Photon emit radius set to be slightly larger than the area of interest in the view?

 

In general there is nothing wrong with the settings so it must be down to the shaders, mrSun shadow sample and finaly geometry. Can you post a render of the scene

 

jhv

[Stan Zaslavsky]

i would also try turning off GI and increase the bounces for FG to 2 and bring down the scale of the FG Precision Preset to Draft.

Then see what the effect of this is - and then increase the FG to Low or Medium preset.

See the result of this and if it speeds up the render and gives you the results you want without GI.

[Crazy Homeless Guy]

If the lighting solution has calculated, and the image is taking awhile to render, then I would guess that the problem is probably due to poor setup of materials by using to many samples, or having your AA set to high.

 

Your AA is fine, though I would switch to Box instead of Mitchell. It will render faster, and then you can sharpen in Photoshop using an Unsharp mask.

 

So, ...that leaves the samples on your materials. Do you have a lot of glossy reflections? ...if so, how many samples are you typically using on them?

[Macer]

I'd up your spatial contrast too. For an exterior scene you can probably get away with .07 -.08, mind you this is scene dependant. This will reduce your render time quite a bit...

[berliner]

So I made some changes, primarily to what Justin suggested.. it's seems to help a bit. Here is a sample image with those changes. Let me know what you think. I just changed the overall building material to a composite with stucco-as this is the main finish...

I'm still not sure about the accuracy of the lighting and the overall realism of it..

[mattclinch]

you absolutely will not need GI for that scene. use just FG with multiple bounces and recalculate your FG map and resave.

 

that scene, at that size, even on a bad laptop should take no more than 1hr - 1hr 30 mins.

[berliner]

Yeah you're right. I turned off GI and am testing it out at lower FG values- running much faster. Although, I've noticed based on the image I posted, that the sky background is waay over saturated, lol. Thanks for the tips

[RevitGary]

 

I would switch to Box instead of Mitchell. It will render faster, and then you can sharpen in Photoshop using an Unsharp mask.

 

I have done tests on pretty complex scenes and did not notice much difference in time when using box over mitchel.

[Crazy Homeless Guy]

I have done tests on pretty complex scenes and did not notice much difference in time when using box over mitchel.

 

Hmmm. If I get a chance I will dig up my tests and look again. I think I was getting a 15-20% savings. I am pretty sure sharpening filters in all GI apps tend to take quite a bit longer.

[Justin Hunt]

15-20% is very good, I think the best I ever achieved was closer to 5%.

 

When using FG the two biggest factor for time is the density and Rays per FG point. Obvoiusly the higher these numbers the better quatity and detail but the slower the render.

 

A density between 0.8 and 1 and Rays between 80 and 120 is often more than enough.

 

For some exteriors I have even used Draft preset, Interpolate 100 and 0 diffuse bounces. Such as this one.

 

jhv

[berliner]

I'll check that out also.

@ Justin- regarding the image you posted, I was wondering about the specs on the glass that you used- is it also Thin Glass?

Also, did you just use the mr Sun and Sky for this scene?

[berliner]

Also, did you just use the mr Sun and Sky for this scene?

 

The reason I ask this also is because I'm trying to obtain the same softness in shadows that you have and mine are still pretty dense in some places...

[Justin Hunt]

The glass is a A&D with a light blue diffuse colour, Diffuse level set to 0.3, Reflection 0.5 and refraction 0.5. Yes it is thin wall

 

The sun is default in this case, most of the time I up the shadow samples to 20 to smooth out the graininess. Alot of the softness you see is a result of high FG interpolation and a large AO radius which is around 2 to 3m on everything.

 

One thing I do is play with the exposure control. Typically for an exterior I use MrPhotgraphic with a EV of 13.5 and drop the mid tones to 0.9. This brings out the depth of the tonal range in the image. I also set "affect Backround and environment". Most of the time I comp in a new backround but use the rendered sky as a base.

 

jhv

[berliner]

Thanks Justin, I tweaked some of those settings as well and it really seemed to help. Although, I upped it to 1 bounce in order to brighten it up a bit as well. I really appreciate the tips.

[Justin Hunt]

Yep, normally you'd use 1 or 2 bounces, I was just demonstrating that if speed was the most important thing then even with crazy low settings it is possible to get a pleasing image.

 

jhv