The principle of lighting the scene to get that kind of effect is no problem, but I seem to end up with extremely noisy highlights, and I’m unsure which settings I need to concentrate on to clean them up…
I’ve got my geometry samples for the motion blur set to 12 and noise samples to 0.005, with cubic AA.
Is there anything I can do to smooth out the highlights and stop them looking so jagged and broken?
One option is to clamp the HDRI for the reflection, but this of course reduced the intensity of the highlights.
I hope there is something that can be done about this. By the way, progressive sampler seems to handle this better then bucket.
I hadn’t seen either of those threads, so they made interesting reading.
One option is to clamp the HDRI for the reflection, but this of course reduced the intensity of the highlights.
In this case, it’s not a bright part of an HDRI that’s causing those highlights, but a single VRay light that I’ve added for the very purpose of getting the highlights.
I’m getting slightly better results after increasing the geometry samples to 64 (!), but any higher and my render just sits on 0%, which I assume is because I’m running out of memory.
I hope there is something that can be done about this. By the way, progressive sampler seems to handle this better then bucket.
I’ll give it a try. Never used the progressive sampler in over 15 years of using VRay, so probably about time I had a look!
You may have some luck making the speculars a bit broader and softer.
It would be great if you could send the spinning rim and light to support however.
EDIT: while the above helps, also ensure that you have a min AA of 3/4 subdivs at least. While it will be oversampled easily later on during the rendering, it will provide for a better “bedding” to the sampler, making it find detail it’d otherwise miss.
below, samples illustrating what i wrote about above.
From left to right: the scene setup (notice the geo has very fine chamfers on every edge, not quite visible at that resolution), default settings, and a glossiness of 0.95, default settings, and gloss of 0.85, 4/24, and gloss of 0.85, and a crop of a 4-100, 0.01 NT of the problematic areas.
The Geo has 16 moblur samples, and performs 10 whole revolutions (3600 deg.) in 25 frames, while the arealight is at default values..
Thanks for all the samples Lele. Much appreciated.
Regarding the subdivs, I’m already on min 4, max 80, as with min set below 4 I’d occasionally end up with completely black buckets here and there.
Would there be any more benefit in raising either of them further?
As for softening the speculars, I’m giving it a try at the moment, although the original material was a VRScan, so I’m having to substitute it for a simple glossy reflective VRayMtl now.
It’s only part rendered, and it does look cleaner, but the highlights are far broader than I’d ideally like them. I guess maybe I can counter that with a smaller lightsource though, so I’ll keep experimenting.
So, it seems that for the while, the only way to properly clean up these kind of situations, without changing the scene setup, is with brute force camera sampling.
Namely, a 4-1000 (one thousand!) will render Olli’s highlight perfectly fine to a noise threshold of 0.01, while not really taking any longer in the rest of the image which will never reach 1 million cam rays per pixel to achieve the given N.T..
Because of the very high camera sampling needed across the whole screen (the spinning wheel covers it all, there are no non-moblurred pixels), you will be able to shave some decent time from the rendering by lowering MSR to, say, 2.
I heard from a bird specific improvements are being studied, but this should work just fine, with minor variations, across most cases (f.e. with a slightly higher min AA, with a default MSR, and so on.), for the time being.
It goes without saying that this can be helped by lowering the intensity of the highlight in question (f.e., to 2 or 3 float, from 15-20. By whichever means.), which will shave potentially a great amount of time from the rendering.
EDIT: i should hasten to add that the sampleRate RE is your friend: if it shows red, there will be noise left in the image because max sampling has been reached before the noise threshold.
EDIT #2: below, a comparison of the original scene settings (1-32, 0.01) and the new ones (4-1000, 0.01) (left column) and the respective samplerate render elements (right column).
It took a *very* long time, however, in the parts which needed it, and are green in the Samplerate (green at 1000 subdivs. geez. XD).
Bright side? it resolved them exactly, and didn’t take much longer elsewhere.
Please could I grab the scene for a look too, Oliver?
I’m still struggling with subdivs set at 4-1000.
This render took 4 hours at this size, but I’m still getting some fairly red bits in the SampleRate RE, and also some totally black buckets (right hand side of the two highlights on the right)…
That’s for Ollie to decide.
To be clear, however, on what is problematic in these kind of scenes: if you render it without motion blur, you’ll notice the streak is a *very* bright highlight.
That alone will need -currently- a lot of sampling (other engines downright clamp. and good night.), because lowering noise in high energy pixels is a challenge.
The motion blurring makes the statistical chance of finding that highlight smaller (depending on moblur and motion parameters), requiring more samples to ensure it’s found, and that shoots the rendertimes through the roof.
Further, this can be compounded by color mapping on either side (either not LWF, or the image has grading in the VFB showing different values than they really are.).
I speak of this because the contrast ratio of your shot looks off (on two different calibrated monitors, at that), with the blacks too black, and the highlights seemingly too bright (i can only judge them by the core-to-tail ratio, the image being LDR).
I could suggest to leave max AA unbounded (set it as high as it’s able to go), raise the min samples still (6/8), and to make buckets bigger to avoid those cutoffs.
But it sounds way too extreme for the kind of shot that is.
Without that scene, or any other which is misbehaving, i can’t tell you for sure what it is which isn’t working properly.
FYI, we are bound by implicit secrecy, so no data will be made public (in the case of Olli, i assumed he wanted -at least a little crop- for public consumption.)
Further, this can be compounded by color mapping on either side (either not LWF, or the image has grading in the VFB showing different values than they really are.).
I speak of this because the contrast ratio of your shot looks off (on two different calibrated monitors, at that), with the blacks too black, and the highlights seemingly too bright (i can only judge them by the core-to-tail ratio, the image being LDR).
It is LWF and there are no adjustments in the VFB. It’s just underexposed as it’s lit by a single small light, with the intention of adding it over the top of the HDRI-lit hero render.
To give you an idea of where the brightness should be, it’s a white car.
Without that scene, or any other which is misbehaving, i can’t tell you for sure what it is which isn’t working properly.
FYI, we are bound by implicit secrecy, so no data will be made public (in the case of Olli, i assumed he wanted -at least a little crop- for public consumption.)
Sure. I’ll try and chop this one up and send it over shortly. Thanks Lele.
Sure, John. Please tell me where I should send it to.
Are there any guidelines or rules to follow regarding the motion blur settings, just to make sure the sampler is finding these important pixels? I imagine one single revolution of the wheel would be sufficient, if the camera exposure is long enough to make on spoke a “blurred streak” of exactly 360°, no? I hope this makes sense…
I am rendering a test right now, but I have to say its sticking to the blurred highlight for nearly 6 hours. But it looks clean I have to say. Will post the result later.
