AmbientLight for Foilage - but Enable GI for rest of scene - Forest Pro objects

[Morne]

Hi all

I have a scene with lots of foliage. It takes long per frame. Using BF and LC. For foliage thought I could bring render times down by excluding it from GI, and using Ambientlight instead. It look ok(ish) but obviously not like true GI. Anyways the look isnt the problem (for now)

The problem is using the ambientlight and including only the foliage - forest pro object - doesnt cut much of the render times as I expected. I'm saving maybe 5% only. Was hoping to cut about 30 to 40 percent of the times.
For the forest objects I went into vray properties and switches off all GI settings.

Am I missing something, or does 5% saving sound about right? (The rest of scene still use GI) but I would say about 70 to 80% of the scene is made up from forest objects (foliage)

[alexyork]

The main issue with rendering forests is that the details are tiny, super tiny compared to the rest of the scene, so require extremely fine AA to resolve without giving you a noisy result. The GI/FG/IR etc. is not really that relevant, as you've found - the best solution there is what you did, by using regular direct lighting. But you can't really get around the AA issue, and that's your main problem. There are various tricks, one of which you can try is to render at double resolution but lower AA settings, then down-res the frames. This would hopefully speed things up plus result in a blurry image, thus removing some/all of the noise. You can also experiment with different AA filters etc. For sure, remove any specular and reflectivity from your forest objects to remove speckles/flickering etc.

It's one of those things you'll probably have to solve with brute-force methods of really fine AA and lots of render power, or look into tricks to get around the issue.