Is BF getting close to the speed of IRR, or is IRR always going to be faster? If IRR is still faster, by how much? If I set me IRR to a high preset, after the 4 passes, and the actual render, it doesn’t seem that much faster. With the last couple V-Ray releases, at least, BF is the default. Why is this? Is it just because it’s more. Accurate?
As I remember, at the time Vlado was saying that the BF routines were recently upgraded and were significantly faster than they previously were - and that’s when I noticed that that BF was the new default for the primary GI engine. …And certainly an unbiased rendering is going to be more accurate, ray-wise, than a biased one.
But to my knowledge math-wise, biasing in general should typically be faster than (at least relatively) pure path tracing, so I’d imagine that in general IRR mapping is still going to be faster pixel per pixel than Brute Force - at least most of the time, anyway. …And this is what I have seen in the tests I have done since that Upgrade…
I’d like to do some more testing though…
Generally, I get the feeling that the general movement is to eventually do away with biasing altogether, along with all the time it takes to get it right, especially with animations. And I guess that’s another reason you see these defaults change over time…
Just my observations…
-Alan
gotcha, thanks. I still see photon mapping and remember when that was the engine of choice for interiors (I think it was interiors).
Well BF technically isn’t unbiased unless your talking BF + BF. Since we use lightcache as secondary as default it’s all Biased, but can your really tell a difference ever. Close enough in my book. As far as IR vs BF, I find IR to be around 3x faster. That’s a great jump from before which it was like 5 or more times faster. Now BF in RT is really fast, and just imagine IR in RT.
you say that IRR is 3X faster than BF, however, IRR has several presets. I just waited 2 hours for the IRR high preset to calc prior to rendering. When people give their times, I wonder if it’s with, or without pre-pass? BF doesn’t have pre-passes. I guess my question is, 3X faster using what preset?
I would personally never use High preset, I put it on low and adjust the settings accordingly. Also using low with good settings and using detail detection give you much better quality closer to the look of BF. Honestly if you are having trouble figuring it out use the Vray quick settings. They take a lot of the guess work out. Try this in using the vray quick settings, click interior, make sure it’s IR + LC, go to IR and turn on Detail Enhancements. Quite of a lot of situations you don’t even need Detail Enhancements, and if you can do without it will help reduce render times quite a bit. Leave GI quality at 0%, set shading rate to 6. Change bucketing to Progressive and set the AA max sub to 6. From there up it to reduce the noise. See the times and quality you get, let me know if that helps at all.
Your asking about prepass but that is for animation normally. I’m talking about calculating IR at each render since working on it or single image you might be changing things, so leave the mode at default single frame.
I’ll give it a try.
You have to ask your self, do you like the biased look of irmap? for example if you set it to -3/-1 and in the areas where objects are close to each other you see blurry shadows (where they should be defined). If you raise irmap settings until its crisp, it will be almost same as bf, and therefore the render time will be similar.
Gotcha. It makes sense.[quote=“Morbid Angel, username:Morbid_Angel”]
You have to ask your self, do you like the biased look of irmap? for example if you set it to -3/-1 and in the areas where objects are close to each other you see blurry shadows (where they should be defined). If you raise irmap settings until its crisp, it will be almost same as bf, and therefore the render time will be similar.
[/quote]
Well in theory (not quite in practise) reducing the min rate will sharpen those contact shadows while still allowing the imap to undersample the big flat areas. That is where the speed is gained. However a couple of things I’d note: 1, the imap engine has not been updated for ages. I’m sure if some of the techniques used to improve BF recently were applied to the imap engine, it could be improved further speedwise. And 2: in the case of multiframe incremental for fly through animation, the speed advantage over BF is still extremely compelling, and you can afford to do an extremely sharp Imap (min rate of 0 or even 1, with high subdivs and minimum interpolation.
Wrt. Setup, I usually switch to the medium preset, then, for a print resolution (5-6k horizontal) Image, I set the min rate to - 10 or 11, and the max rate to - 1 or 0. Then I reduce the interpolation to 10 or so, and crank the subdivs until the splotchies are gone. Problem with the presets are they are not designed for high resolution work. The min rate is much too high (low), meaning lots of unnecessary samples and low speed (plus more noticeable blotches) on the flat areas.
What do you mean by reducing the interpolation?
Okay, you are talking about the Interp. samples. Got it!
Its true about multi frame advantage, I actually asked for a feature to cache bf in same way. In my tests though you can get a sharp clean irmap which will be cleaner then bf in about same time. But these days its not just gi that slows things down. For example reflections and glossy reflections and multiple light sources also slow down rendering. Even without gi. So even if you speed up gi, you still get bogged down by other areas.
I read something about exteriors with an HDRI not needing GI enabled for a blazing fast and clean render, but it didn’t make sense, or I missed something.
Bobby Parker www.bobby-parker.com
Gi is just a bounce, a fill light if you will. In exterior its less noticeable bec its illuminated from all directions, in interior it would play a much more vital role as bounce light.
yes a “multiframe incremental” for BF would be awesome. ive asked a number of times for variations of that or an “unbiased” mode for the imap. its sadly impossible to turn off interpolation for the imap, set the min and max to 0 and get a bf solution. its WAY slower tha BF and looks awful.
I wouldn’t image it worked for most exteriors. I realize that it is light bouncing around, a lot of the image would be dark.[quote=“Morbid Angel, username:Morbid_Angel”]
Gi is just a bounce, a fill light if you will. In exterior its less noticeable bec its illuminated from all directions, in interior it would play a much more vital role as bounce light.
[/quote]
Here I’ve done some tests (I apologize in advance for any inconsistencies I have two kids bouncing on me as do this):
Its a free scene from the web. I like to use it because it has a variable level of complexity, carpet, and wall decor take a bit of time. I’ve used very simple settings:
base settings adaptive dmc 1/24, with 0.01, all unclamped with no subpixel, only max ray intensity (all defaults)
irmap/lc
lc is default all with 1200 samples
shade rate is 6
irradiance map medium preset with -3/-1 and 100/50 and clr thresh of 0.2
dmc 1/24 and 0.01
You can see irmap is pretty clean though there are edges of the ceiling which suffer from common irmap precision problems since its max rate is -1 and not 0.
http://postimg.org/image/xgtg7lqzx/full/
Second render is bf/lc
http://postimg.org/image/en7nalsrx/full/
You can see that the bf render is a bit more grainier and took 6 minutes where are the irmap is 4. Neither of them satisfy me to the fullest extent - irmap render needs higher samples for more accurate shadows, bf needs higher samples for less noise.
Both renders spent extra time in the detail areas, for irmap it took 2 minutes for prepass and spent lots of time in the carpet and decor. I also find that because irmap is interpolated the grain from lights stands out quite a bit, so you get clean wall with grainy light edges.
Next I took irmap and went from -1 to 0 and render time went up to 8 min 40 sec. This is mostly on prepass as the actual render was very fast. I can say that with this quality its acceptable for the edges and precision, I’ve also reduced the hsubdivs and interp samples to about 3rd for 0 res its applicable. I’ve set the noise thresh to 0.006
http://postimg.org/image/mii6pf2el/full/
I would say that I actually spent more time fiddling with irmap (tests) to get a good result then with bf so if you take into account several test renders I did to get it to look good it might offset the total render time for irmap frame.
For brute force I’ve just lowered the noise thresh since its the only way to get it cleaner to 0.006 and the render time was 8m 59 sec which is just a bit slower then irmap. But this solidifies what I said earlier.
http://postimg.org/image/6dvrw6z1p/full/
super gnu, since new vray’s msr is pretty good with bf it also flies through the blank wall areas pretty fast.
Lets put this to real test, I’ve disabled the grey override.
Both renders for irmap and bf produced very similar render time.
http://postimg.org/image/dwex4tqel/full/
http://postimg.org/image/y8w46sv71/full/
My conclusion is that with irmap of -1 for max, you can get faster result but at a cost of precision. Otherwise the render time is the same.
yes it is as ive observed in recent builds, but for me this just means imap needs some updating 
when imap was last worked on, it used to be many, many times faster than BF. and it should be.. its supposed to be doing much less work.