I am trying to optimize some render settings and have some questions…
Brute Force as Primary and Secondary is considerably faster than IM/ LC, and the RGB looks extremely similar.
When optimizing my settings I look at the Raw GI, Raw Reflection, Raw Refraction, and Lighting.. My Raw GI is insanely noisey with BF/BF, but the RGB doesn’t seem to reveal this
My question is- should I care? Normally when optimizing settings I would think that’s a problem but my RGB looks as clean as my IM/LC render. I’m just hesitant to use it for some reason! I’m so used to IM/LC and looking at these passes to tell me what to optimize If my Raw GI looked this noisey using IM/LC my RGB would look like total crap but for some reason I can get away with it in BF/BF?
You should be looking at the “GI” element, not the “Raw GI” one. It’s normal that the raw GI is noisy - V-Ray optimizes its sampling based on the RGB output, and as long as this is fine, V-Ray doesn’t care how the individual raw render elements come out.
Ah silly me, I just did another render with normal GI and its considerably smoother than the raw gi.
Another question related to BF- why is it so much darker than IM/LC? I’ve tried upping the BF subdivs and depth to 128 & 32 and couldn’t get it back to how bright it was with IM/LC
id advise using BF and LC. this is the ideal choice these days. BF/BF is too slow for very little (no?) improvement in final image quality.
the reason BF/BF is darker than im/lc (or BF/LC) is that BF by default does 3 secondary bounces. even turning it up to 32 doesnt come close to LC which does 100 bounces by default.
you could turn BF secondaries up to 100 bounces and wait for a month, or just use LC like everyone else.
the reason “normal” gi ( do you mean IM /LC ?) looks smoother is its interpolated. if you are referring to BF/LC they its probably less noisy since the BF primaries are being calculated from a lightcache, which is interpolated and smooth, giving the BF engine less work to do to arrive at a clean image.
edit:
-ok i just understood you were referring to the “normal” gi pass, not another gi calculation method.
I normally stick with IM/LC myself but after some time optimizing this scene (exterior of a car lit only with dome light) I found BF/BF or even BF/LC is significantly faster and no noisier than IM/LC.
BF/BF was twice as fast, and BF/LC was about 30% faster still than IM/LC.
I tried upping BF GI Subdivs to 128 and it was still darker than IM/LC (still twice as fast though). Where are you saying to turn up BF secondaries? When I switch Secondaries to BF I lose any settings for secondaries except for the multiplier.
hm.. unless 3.1 is different than on max (im a max guy) you should have a “bounces” control in your bf secondaries. its default at 3 bounces. subdivs will make almost no difference to brightness.. its the bounces that are the issue. are you sure you are looking at the “expert” interface?
ive literally never heard of a case where BF/BF is faster than BF/LC, or IM/LC. there are geological processes that are faster than BF/BF whenever ive tried it. to be fair though ive not tried it since vray 3, since BF/LC works so well.
edit: ive just noticed your scene is an exterior car shot with a domelight, so Gi is extremely easy to calculate in this case… my experience is generally with architectural interiors.. youd never go near BF/BF with a bargepole.
In Maya there isn’t an ‘expert mode’ to reveal more control, that I know of at least? I know what you are talking about as I used Vray 3 in Max before too, I haven’t seen that option in Maya and didn’t think it existed in Maya. But I don’t see anywhere to control secondary bounces for BF so maybe I’m missing something?
Hmmm BF/LC even with BF depth at 64 looks no different than BF/LC with depth at default of 3. Is there a way to get that same brightness/ intensity as IM/LC with BF/LC or BF/BF?
So I went to make a test scene and couldn’t recreate this. I went back to my problem scene, loaded the default render preset to reset everything, and now I’m not having this problem. Perhaps I was just tired…
Just wanted to add my own personal experience to this thread. BF/BF can actually be quite competitive in terms of speed, while producing much more reliable and consistent results (especially for animation work). But it all depends on your subject matter, format, and definition of “fast.” I’m mostly involved in HD product work, with the products typically placed in interior settings, and my target render time per frame is around 25 minutes.
For me, BF/BF speed is totally acceptable when setting Subdivs Mult to 0.000 (letting Vray control subdivs), cranking the Min Shading Rate (higher values gradually improve shading/texture/noise quality vs. antialiasing quality) to something like 20-30, and then gradually working the Adaptive Threshold from .020 down until the time/quality balance is acceptable, usually around .015. I’m also doing a slight amount of grain management in post.
I’ve been having faster renders/ lower noise with lowering my thresholds to .005 and keeping min shading rate at 1, as opposed to cranking min shading and keeping threshold above .01. I need to do more experiments though that’s interesting you’re going as high as 20-30 for your min shading rate and your thresholds that high.
FWIW im focusing on car exteriors right now just lit with dome.
Others can probably explain it better than me, but my understanding is that the Min Shading Rate controls whether samples go to antialiasing (lower values) or shading/noise (higher values). Far fewer samples are needed for antialiasing than shading, and moving this value up shifts the samples accordingly. It basically makes better use of the samples, reducing the need to drop the threshold so low, which is a much costlier way to achieve the same visual result.
This may be completely wrong, hopefully someone can clarify if it is.
Yep - minimum shading rate is forcing that number of shading samples to be cast every time an anti aliasing ray is shot. The logic is that the anti aliaser only sees the final 2d image pixels when it’s doing it’s quality testing and it’s looking for differences in colour or brightness to smooth out - these differences or just “contrast” can be anything. It can be areas of detail in a texture, it can be the geometric edges of an object lying against each other, or the important on in the case of speed, it can be noise / grain in your shading. If you’ve got a totally flat plane in your scene (such as a floor or wall in an interior) there’s no geometric detail to worry about since it’s large single polygon areas, but if the light or material hitting that wall is noisy, the anti aliasing sampler sees that as noise and it’ll keep going through cycles of anti aliasing trying to clean it up. Say for example you have vray set so it’s only taking one light, gi and material secondary sample per anti aliasing ray, and it’ll take 50 of those secondary samples to clean up our wall. That means that vray has to shoot an aa ray to get one secondary sample for each, test it and see if it meets your chosen quality level. It won’t, so it shoots another aa ray to get another set of secondary samples, tests them, again fails our quality test and goes again all the way up to the 50 samples it needs. Now we have the option of using min shading rate and if we set it to 10 for example, every time vray shoots an aa ray, it’s forced to take 10 light, material and GI samples. If we do this, it’s only going to take 5 rounds of our sampling loop to get up to our 50 samples needed for a clean result. All of the overheads of the loop of sampling and quality testing take a little bit of time so you can get faster results by trying to kill off the loop of sampling earlier on.
There’s lots of stuff being looked at in this area right now to make it easier, it’ll be an interesting few months
wow, this is impressive “universal mode” alternative. Rather than letting materials do the subdivs and lights, this way has made a recent scene render so much quicker. Thanks for sharing it.
If my Raw GI looked this noisey using IM/LC my RGB would look like total crap but for some reason I can get away with it in BF/BF?