How to render both small details and large areas

[jmottle]

We are having an issue with one of our files trying to find a compremise between seeing the detail we need and eliminating blotchyness.

We have a condo tower that has one side that is lit with skylight and direct sunlight and the other side is lit with just skylight. All sides have small reveals cut into the building face and it is important that we see them. We have been able to make them look good by adjusting the Min and Max rate for the irrandiance map, but then we start to get other areas of the model that are in skylight only that look really blotchy.

It seems as soon as we fix the blotchyness we loose the shadow in the reveal. We have experimented with AA, HShp, Inter Samples, Dist, Threshold...but nothing is working...


Any suggestions as to how you can have a clean image AND fine detail?

[percydaman]

it can be difficult man. A pic and screenshots of some settings would be more helpful though, as there is no real magical settings.

[timmatron]

Can you post a shot of what you are working on?

If you are not rendering close up but still need to see those clean reveal lines, you could always cheat and fill in the reveals and add a dark matte material to it to simulate the shadow. I've done that before, because sometimes Vray is a pain with little details like that - you see them in some buckets, and in others they are gone.

Have you tried the Catmul Rom AA filter? Thats really good for getting those little details.

If you are using Area filter, try reducing the filter size to something smaller than the default 1.5 and see what happens.

[Gijs]

Are you using latest betaversion? Then maybe you can try a different GI method lightcache+QMC. I have found that in cases where you need sharp details, the abobe method is eventually faster than irradiance map. and predictable results when you control the quality with QMC sampler.

[flipside]

Gijs, do you mean lichtcache for first and QMC for second?

[Gijs]

No, first QMC, secondary rays lightcache. It has its price in terms of calculation time of course, but tweaking irradiance map settings is not my hobby.

[flipside]

Ok, that sounds more logical than LC in first

I like QMC too, but the problem is that if you double the resolution with IR map, you can lower the min/max and calculation time for IR will stay the same. With QMC I think it's almost impossible to do high res renders in a reasonable amount of time.

[CCS]

I know what you mean. I wish it weren't, cuz I really like the look of QMC+LC. Not quite as "soft" as IR. Has a nice edge to it. Hard to keep the noise out though - especially as the image gets bigger.

[Gijs]

That's right, but you save some time when you don't need to tweak irradiance settings. And once you know how Vray's nerve center works(QMC sampler) you really feel in control of Vray.

[flipside]

Hi Gijs,

can you show us some examples where you use this setup, with rendertimes? I'm interested in what you can achieve, maybe some examples can convince me to try it also

[Gijs]

Well, I wouldn't recommend it for all types of scenes, but it is great for product rendering (comparable to outdoor rendering). Interiors benefit the most from irradiance maps. But as jmottle described an outdoor scene, QMC+LC is fast.
I use it mainly at work for product renderings, which often have very small gaps between parts. Those are terrible to render with irradiance map. Or your irradiance map settings have to be set so high that you lose the benefit of undersampling. The material I have with this setup is confidential, so I cannot show it here.

[flipside]

Ah ok I see, was thinking about interiors all the time

For products, I have to give the QMC a try indeed. Altough untill now, IR map didn't give me any troubles, but it depends a lot on the materials and lighting setup too. Usually I have some area light which creates the fine shadows everywhere, and materials are very reflective so you don't need a good Gi solution to see the fine gaps, creases or bumps

bye,

wouter

[room217]

jmottle, this has been an issue with us for years.

One solution is to use renderable lines in place of the reveals. Color them dark-ish and turn off shadow casting.

In a dream world I'd like to have modeled reveals for close ups and renderable lines for the rest.

good luck with the rendering.
-randy

[skogskalle]

wouldnt ppt be the way to go here? for exteriors I think its rendertimes are OK, and if you let it render over night Im sure the quality will be great...

[jmottle]

Thanks for all the feedback guys. We tried all of the solutions reccomended and a few others, but in the end I think we have come to the conclusion that the render times involved to make it look right are not worth the effort or time when compared to cheating with renderable lines as randy suggested. Ahh well, we did learn a fair bit in the process.

Cheers,
Jeff