Hello all;

Sorry, this is a subject which has been raised already, but I’m on a tight deadline and need some ideas… not much time for running multiple render tests to get an optimal setting.

GI interior (but no ceiling), fairly simple model but render is 2048 x 1024. I’m getting GI artifacts/flickering in the animation, most noticeable in the shadows, which is greatly reduced when I render a 1/2 size or smaller draft with same ray count. Settings are:

Primary 200, secondary 0, other settings default. Using adaptive skymap.

When I up the ray count to 500 I get untenable render times (8 mins/frame on a single 2GHZ core as opposed to 2 mins for 200 rays)

Also getting some edge sizzling in fine detail areas (rounded corners etc) - fixable by upping antialiasing/sampling in render dialog I suppose?

Any tips for smoothing these out without blowing render times would be much appreciated!

Thanks
Rory

EDIT: I fixed the detail/edge flicker/stepping, it was a common or garden sampling issue as outlined in the manual, but still having probs eliminating the GI noise.

Hi Rory,
Unfortunately GI noise is always a problem in animation.
The GI samples are not held from 1 frame to the next- each frame uses a different set of random samples- hence the noise “flickers” from frame to frame.

General guidelines for eliminating noise-

1) decrease the sampling grid to 4x4 or 2x2
2) increase your Primary rays to 400, 600, 800 or more

Increasing the rays or decreasing the sampling grid WILL increase render times. There is unfortunately just no way around this, but if you generate enough GI samples you can eliminate GI flicker.

Hi Rory,

Further to Dave’s advice, you can also increase the Colour tolerance setting to 4 - this will break the GI ‘blotches’ up more and make them a little less noticeable.

Decrease the sampling grid size first (from 8x8 to 4x4 etc.) before increasing the ray count. Typically, you want a minimum of 200 rays for animation.

Best,
Ian

Hi Ian and Dave
many thanks for the tips. Your advice to decrease sample size before increasing rays looks like it’s borne out by my render - still blotchy at 400 rays, no other settings change. I set it going before I saw your posts unfortunately!
thanks again
Rory

Sods law

It also depends on the scene:
Say you have plane colours on your objects (flat green etc.) you’ll need LOADS of rays (300+), and a small sampling grid. However if you, for example, have a brick texture on all your objects, you could probably get away with 150 rays as the noise will be hidden by the maps.

I hope you have more success!
Ian

Thanks Ian, yes it’s the plain-coloured walls which are problematic, the parquetry floor is fine.