Problem with blotches on interior

[tricky]

I'm using SP3 64bit and Max2009 64bit. I have an interior scene and I am really struggling to get rid of blotches all around corners of geometry. These blotches aren't just around the ceiling like I show here, but almost everywhere that there is a 'corner' like this. I'm confused as I've never really had this level of problem before. My settings are reasonably high already.

I'm using vraysun and vraysky, a vrayphyscam and various 'fillin' standard max omnis. Nothing special really. I've also just tried a new coffer light using the new vraymesh lights, but the problem existed before then. The model is generated in AutoCad architecture and file linked in (as we have always done) and the geometry is pretty clean - ie there are no silly gaps at wall/ceiling junctions. It is modelled as we have always modelled. There is 1 max spotlight being used as a projector (the blown out bit at the bottom of the image), but again, the problem exists without this.

By the looks of things I am having an issue with the coffer mesh light and DR, but I'll worry about that later.

Anyway, a few images will hopefully explain things:


Here's a render with an overide vray material:



And here's a render with the same mtl overide but with all lights apart from vraysun (and skylight) off:


So here are my settings:




and finally:


I'm really hoping I've overlooked something obvious here.

[Pictor2]

I'm no expert but unless it's being animated should the light cache not be set to screen instead of world with sample radius .02 or thereabouts? -10 on the irradiance map min looks a bit low too, try -3 perhaps and see where that gets you?

[tricky]

I don't think setting the LC to screen would make too much difference, but I'll try and see if it helps. Also, the -10 will allow me to have a smooth IM for large flat surfaces and anything in between -10 and -1 will be calculated at any rate, so setting the minimum to -3 should make no difference (I think).

[vlado]

It looks like the light cache is not smooth enough and causes the blotches near corners. So you need either more subdivs for the light cache, or you need to blur it more (using either more samples for the light cache Filter, or using the Prefilter option).

Best regards,
Vlado

[natty]

Hi

your Global subdivs are set to 0.01? this surely aint gonna help.
you have a very odd mixture of settings going on here, i would personally set you LC back to screen for a scene like that, Have "use camera path" and "Adaptive tracing" ticked, turn on pre filter and set to 100, Filter on fixed.

i would also change all your IRR settings and AA settings as well, but see how the LC looks now.

[tricky]

Hi

your Global subdivs are set to 0.01? this surely aint gonna help.
you have a very odd mixture of settings going on here, i would personally set you LC back to screen for a scene like that, Have "use camera path" and "Adaptive tracing" ticked, turn on pre filter and set to 100, Filter on fixed.

i would also change all your IRR settings and AA settings as well, but see how the LC looks now.

Natty

The global multiplier of 0.01 means that all dubdivs are effectivly set to 1. I am then using the QMC sampler (set from 1 - 18 to control the global subdivs, so effectivly, where it is needed, vray will use 18 subdivs. Its a lot easier this way I find.

Again, the AA filter is off as I am letting the QMC settings control everything. Besides, turning it back on wouldn't affect blotchiness - only edge smoothing/sharpening etc.

With regard to the IM settings, what would you change? They are very high quality settings already.

[tricky]

It looks like the light cache is not smooth enough and causes the blotches near corners. So you need either more subdivs for the light cache, or you need to blur it more (using either more samples for the light cache Filter, or using the Prefilter option).

Best regards,
Vlado

Will try this. I did notice that the LC isn't looking particularly smooth. Its strange: ith still images in previous vray versions, I've never really had to bother upping the number of samples from the default 1000 or need to use the prefilter options (or changhe it to World units which I have tried in my posted example as it was just one of the many things I was trying to solve this). So its either this scene which is being particularly awkward or something in SP3 is different. Could anything in SP3 have changed that would cause what I am experiencing?

[tricky]

Well, it turns out I had obviously tied myself in a knot through panic testing over the last day or two. It was simply a combination of upping the light samples to 2000 and switching back to screen scale! I'm annoyed with myself now as I've never used world scale in the LC for anything other than animations!

I'm not sure if LC pre filtering makes so much difference in this case.

Thanks guys!

[natty]

HI i understand the workflow, but not something we have experimented with.
glad you sorted it.

N

[tricky]

...I thought I had but I still have problems! 3000 LC samples now set to 0.02 screen res, pre-filter set to 100, IM as before. The blotches have reduced, but not by that much! Ahhhggghhh! There's me thinking I *knew* Vray!

[natty]

i think you would be better off resetting your vray and dont go down the Universal settings.

do you have a scene i could look at and set up for you ?

[jow]

Tricky, try upping the IR map min rate to -4/-3 as pointed out earlier. I had the same problem recently, i was using a min rate of -7 or -6 and getting the same results. upping it to -3 fixed it.

[natty]

Tricky,

can you try our settings which give us clean renders every time.

i do understand your settings but as you have found out the universal settings don't always perform as expected in some cases.

[tricky]

I will give that a shot Natty - thanks.

<Natty, your settings certainly help. Thankyou again. I'm not quite sure why - looks like I may have to re-learn a few settings (for the umpteenth time!)>
...walks away from the forum in an embarrassed kind of way thinking he 'knew' vray...

[tricky]

Tricky, try upping the IR map min rate to -4/-3 as pointed out earlier. I had the same problem recently, i was using a min rate of -7 or -6 and getting the same results. upping it to -3 fixed it.

I will also give this a try. I'd be confused if this approach did work. I always assumed with large, flat areas, it is best to have the minimum very undersampled.

At the moment, I am using LC and Brute force which, although slower, is giving me results. There is a slight grain over the whole image (down to not enough brute force samples I guess, but I have to render 'cleaness' against render times) but it is much more pleasing to my eye at least.