slow render time

[sdwhitton]

Hi There

I'm rendering a scene now, pathtracing, about a million polys, one hdri, a fair few glossy materials I guess, some with an image for the specular, bumps maps etc

rendering at 3200 x 2000 pixels, number of refractive / reflective bounces set to 4

on a GTX 470, 1248 RAM

admittedly on an old overclocker vista (!) machine, 8 gb ram (DDR2!)

but it's saying 11 hours? Target samples level set to 12000

Is this about right do you think? just that I noticed other images on the forum being rendered in a under an hour or so..


many thanks!

[t_3]

Hi There
I'm rendering a scene now, pathtracing, about a million polys, one hdri, a fair few glossy materials I guess, some with an image for the specular, bumps maps etc
rendering at 3200 x 2000 pixels, number of refractive / reflective bounces set to 4
on a GTX 470, 1248 RAM
admittedly on an old overclocker vista (!) machine, 8 gb ram (DDR2!)
but it's saying 11 hours? Target samples level set to 12000
Is this about right do you think? just that I noticed other images on the forum being rendered in a under an hour or so..

many thanks!

this depends on ... just everything my personal "record" for 12000s/pix (3840x2560) was over 80hrs on a gtx 570 (about the same performance as your 470); in fact i let it go on for 440hrs to full 64ks/pix, just to test if octane/the pc is able to constantly render for a long time.

btw, as the render time -of course- depends on the rendered resolution, the ms/sec count is easier to compare. my scenes (medium complex usually sunlit interiors) typically run at 1-2ms/sec on a single gtx 570...

[t_3]

ps: to question is, if you really need 12ks/pix for an acceptable image. again depending on the scene (and some render kernel optimization), a value between 2k and 6k might be already enough; what of course results in a substantial render time cut...

[sdwhitton]

ah ok - thanks for your reply!

Yes, I'll see if the sample level could be lower, and yes it's around 1.7 mSec thingys

what are the big hitters in render times?

I could optimise the geometry, or do I concentrate on the materials? less glossy ones, no glass etc

[t_3]

ah ok - thanks for your reply!

Yes, I'll see if the sample level could be lower, and yes it's around 1.7 mSec thingys

what are the big hitters in render times?

I could optimise the geometry, or do I concentrate on the materials? less glossy ones, no glass etc

well, a trick i have read of (but never done) is to render an interior scene without the ceiling - this will of course only work in some cases. apart from simplifying geometry - if you do interiors lit by hdri enviroment or sun - the use of portals should help, and also to render windows without glass (if possible). if there are additional (inside) emitters, the sample_rate parameter can help to reduce noise (and thus lower render time). also playing with some render kernel parameters might help in some cases (like rrprob). rendering closeups from a bigger scene, it'll be a good idea to take everything out, that doesn't add to the shot.

from my experience, there are no real "big hitters". the more complex a scene gets, the slower it renders; but for me render times are only 2nd or 3rd priority, so there might be still better tips...

[sdwhitton]

OK - thanks again - you might have to explain both the rrprob setting, and portals to me...!

[sdwhitton]

here's the render btw..

[sdwhitton]

this is how it's turned out in the end, well nearly, need to add some glass, maybe over-expose the exterior, and make the sofa look less 'greasy'...

just switched back to Ambient Occlusion, with a sun...

see what you think,

cheers

Steve

[roeland]

Hi,

Radiance made a tutorial about portals in our resources and sharing forum: http://refractivesoftware.com/forum/vie ... =21&t=7210.

The rrprob (Russian roulette probability in full) setting determines how much time the renderer spends on calculating light that reflects a lot of times in your scene between leaving the light source and arriving at the camera. A low setting will speed up the renderer, but can introduce more noise in scenes where light tends to reflect around a lot of times (for example between the walls of an interior). The value of 0 is special, it means the renderer chooses a value automatically from the reflectivity of the surfaces in the scene. This should work well in most scenes.

--
Roeland