Caustics quality
I see you fixed the mesh problem on the coins :lol: (sorry about that)
Yeah, the QMC looks promicing quility-wise, but that image will take a lot longer than 2 hours… I mean those caustics look nice and we might be tempted to think “it shouldn’t take much longer to fill in the rest of the grain” …but… from my experience with brute force solutions, it will take quite longer.
Caustics quality
Here’s a similar test as yours, IR+LC only.
I used 0.5 for adaptive amount, -3/1 for min/max, clr=0.25, hsph=110, raised all glossy subdivs to 40, raised the dof subdivs a bit.
These were just ‘guessed’ settings, the only goal was to prove that you don’t need such a low adaptive amount. Maybe the result would have been the same if I left it at 0.85. I don’t use delone and I used sample value of 12 instead of 20. Also here, you see this doesn’t always mean more noise, if you use high enough hsph. It simply keeps GI sharper. I know you spent 90h on this image, but I think I will be close (not on this last test though, that was just 5 minutes rasing every setting). But believe me, I spent way more than 90 hours on testing IR map and LC on vray for max 
Now you will say that there is still noise on the coins, but the same in your render, so this seems to be impossible to clear up, even with that low adaptive amount and huge amount of glossy subdivs.
The cause of it is that really bright area light you have in the scene. If you would use a different lighting setup, which isn’t necessarily less nice, you could avoid this problem. Or maybe even use directional light instead of an area light for that. But then again, there is no area shadow option on that yet. It would make caustic creation much easier though. Maybe you have another scene to test vray with, because I don’t think it is really fair making a decision on only one scene.
Also as I said before, you will not suddenly get a really quick render if you are after this kind of quality. The methods you are using are designed to make renders faster with the drawback of less accurate GI or glossies or whatever. You simply cannot have both: quick render and perfect accuracy. So either choose for a 16H render, or satisfy with a bit lesser quality.
Here my latest test:
Caustics quality
Six hours is not too bad, but then I remember that your machine is 2 to 4 times faster than mine… this means that it might go from anywhere between 12-24 hours if I were to try your settings.
You might be right about the adaptive amount, but on the other hand the 110 hmsmpl is a bit on the exotic side as well… and … you are forced to go -3 / 1 (going from 0 to 1 is substantial bump, much much much more than going from -6 to -3. The -6 to -3 is no more than 10 min of calculation, but from 0 to 1 can be more than an hour or two at 110 samples )
Well, that would be almost unacceptable in my book. I refuse to let a render engine dictate what I can and can’t do with my scenes.
The glow on the right-hand coin was a planned feature attraction as well as the burned out areas. It is these subtleties (or not so subtle) of light that can make a jewelry image stand out.
The main thing that bugs me now is the aliasing on the bright areas. Vlado, if you are following this thread… is there any room for improvement on that aspect ?
You simply cannot have both: quick render and perfect accuracy. So either choose for a 16H render, or satisfy with a bit lesser quality.
Well, I wouldn’t give up just yet. One thing that is quite clear from your test is that the GI caustics method is 6h versus 1.5 hours for the caustics-photon-mapped method on your machine. This means that the photon mapped caustics are about 4x faster (so I was off by a bit on my previous estimate; that they should be comperable)
So, the next thing is, I will try to render again and let it compute and finish the photon map… if I can get it to go down to 6 hours for the same quality then it will be considered good progress (6h is much preferable than 18 ) 8)
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About the -6 to -3, this will not add much to the render time, but it will also not add that much to the quality of GI. I mean if you compare it with the effect of going from 0 to 1. It’s the second number that has the most effect, that is the ‘max’ value. This also determines the GI sharpness, for example going from -4/-1 to -4/0 will be much better quality than going from -4/-1 to -3/-1.
I use high hsph because I wanted better GI only, not better DOF of better glossies. By using low adapt amount, you increase quality of everything, and that I wanted to avoid. 110 was just a guess, I didn’t test anything in between. Remember that going from 50 to 100 for example is not twice as good or twice as slow. 50 means 50*50=2500, and 100 means 100*100=10000! I believe previous test I did had hsph=70.
Problem is as you also mentioned somewhere that you cannot go and test all in between values, having to wait several hours and then see that you needed higher hsph.
However if you need high res output, ir map is a good option, because in my example if I needed to render at 3200*2400 px, I know that I will have same GI detail with -5/-1 as I had with -3/1 at 800*600. In other words, on the 3200px image, the IR map will take exactly as long to render than on the 800px image. This is not the case with ppt or qmc GI, that will take waaaaaay longer to render (but quality will become even better of course)
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That is a very good point !
I was thinking about possible render times from high res images… and this is a good tip. Thanks
Also, thanks for investing a whole lot of your time on this scene, this experience has helped me a lot; figuring out the settings and the values.
-Thomas
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Two ideas from my workflow:
… if you can, use the _renderwindow command for critical areas. I have used it for area shadow noise tests. OK, if you would use a photon map, than it will not work so good.
… if you can calculate high res images without to much time increase, than you could render a high res image → denoise the critical areas → downscale the image. This method help to keep the details and to kill the noise.
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Can you point me in the right direction to ‘denoise’ an image?
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Yes, that is a good way to go for IR+LC. I usually sample small 10x10pt areas here and there and they render within 60 sec at good settings to check how smooth is the GI in that area.
… if you can calculate high res images without to much time increase, than you could render a high res image → denoise the critical areas → downscale the image. This method help to keep the details and to kill the noise.
I would be carefull with that approach. You have suggested it for Maxwell as well, but it may not be the best way to go and I don’t know if it really saves any time). If you double the size of the image then you quadruple the area so the render time goes up.
Instead of scaling up, I would render at the actual rez, but then scale it within photoshop in order to take denoising samples. Also, another way is to copy/paste a few squares of noise and tile them on the side of the image in photoshop (make the canvas larger to have room) and then use those those tiles for the denoiser.
Also, I have found that the built in denoiser from Paintshop pro is just as good and more convenient than using NeatImage.
Vray, is overall quite smooth so we don’t need to denoise too often (except maybe some areas from the DOF or some low noise left from the GI due to incorrect settings)
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Wouter, there is denoising software if you scroll down this post:
I find that the built in denoiser in PaintShop Pro does a very good job. You can lasso-select specific areas (use feathering for the lasso outline) and then denoise those areas only.
Caustics quality
Thomas, you could add IrfanView to your list. It is for free and bring a good upscale algorithm (also used in pro software).
More infos here: http://www.fredmiranda.com/SI/index.html
I use the upscale, if I want to quick print an image, but dosn’t like to render it again. 
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I prefer XnView, have you tried it ? (it is free too and I like it a little more than Irfran view)
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Impressiv list of image formats … and hdr. :shock:
Seems to be a must.
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http://www.chaosgroup.com/forum/phpBB2/viewtopic.php?t=14303&start=0
This thread looks interesting. This fellow is having similar issues starting out, so his progress would be interesting (rendertimes and glossy objects).
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Wouter,
Do you think the missing options: “Use Irradiance Map” and “Treat Glossy Rays as GI rays” on the material editor would play any effect in speeding up the noise on the coins any further ?
Regards
Caustics quality
Definatly not the use ir map option. This is by default on, and if you turn it off, you are saying that the lighting should be calculated by QMC GI on that object. Imagine you have a whole scene which requires only low IR map settings, but there is 1 object that needs to be ultra fine GI quality, then you could turn off the ‘use ir map’ option for that material.
Not sure about the other option.
Vray manual:
Treat glossy rays as GI rays - this specifies on what occasions glossy rays will be treated as GI rays:
Never - glossy rays are never treated as GI rays.
Only for GI rays - glossy rays will be treated as GI rays only when GI is being evaluated. This can speed up rendering of scenes with glossy reflections and is the default.
Always - glossy rays are always treated as GI rays. A side effect is that the Secondary GI engine will be used for glossy rays. For example, if the primary engine is irradiance map, and the secondary is light cache, the glossy rays will use the light cache (which is a lot faster).
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Thanks. I didn’t know it was on by default
Not sure about the other option.
Yeah I was reading that, but without testing I am not sure what the effect really is.
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same here
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Someone (Vlado ? ) posted this at CgTalk.
I think, on the technical aspect, it is the best render I have seen for this scene. It beats the Maxwell images too in terms of clarity.
The only thing … I wish we knew something about the photon map settings for the 5 hour image:
Caustics quality
The caustics photon map settings were 30,000 caustics subdivs for each light; in the render settings: search distance: 0.2; max photons: 0; max. density: 0.04. I’m not sure if the scene scale is the same between the different versions of the file though.
The resulting photon map was huge, a little less than 3GB, but this was not a problem since I rendered the scene on a 64-bit machine with 4 GB of RAM under WinXP 64-bit edition. Even though I used a 32-bit version of V-Ray, the 64-bit version of Windows can give a lot more memory to an application than the 32-bit version.
Also, I should note that the machine was a dual dual-core AMD Opteron at 1800 MHz, so that means 4 rendering threads. If I had to render on a single-processor machine, it would have been about 21h of rendering.
Other than that, the primary GI engine was irradiance map, and the secondary - light cache with 1000 subdivs. “Use light cache for glossy rays” was off. AA was adaptive QMC 1/100, and the noise threshold was very very low - maybe about 0.0004.
Also, while testing the scene, I found a bug in the photon mapped caustics - they were darker than they should be, so I had to fix this first.
Anyways, it’s a very difficult scene (precise caustics in V-Ray in general are hard to deal with); although V-Ray did a fairly good job in the end, I think it should be possible to make it better and faster with less memory… just need to figure out how
Best regards,
Vlado