Hello,
Could someone please shed some light on how I may be able to clean this up?
Thank you,
Scott.
What engines are you using for GI? I assume your primary is Irradiance map. I would up your subdivs and see if that helps.
So I’ve seen this happen to my renders and wanted to figure it out myself. The issue looks like you are not creating enough GI samples to consistently reach underneath that tiny lip of the siding. Sometimes it samples the front, brighter face and the next samples underneath where it gets darker. As far as I understand it, Vray can’t resolve the two without either taking more GI samples or smoothing out those samples. The ‘right’ solution in my mind is increasing your max rate samples to 0 from -1. You can enable those boxes by clicking where it says ‘Medium’ and selecting ‘Custom’. This will increase your render times.
Smarter people than me on the forums may have a better answer. You could raise your interp. samples super high to artificially smooth out the difference in samples, but I’d not recommend it as it flattens the GI solution.
Thank you very much. The learning never stops.
consider min max irmap samples as resolution of the irmap it self. If you want the resolution (precision or quality of gi map) to be high, to hold up to your image 1 to 1, set the max samples to 0, or 1 for fine areas.
in exterior settings though, you can get away with brute force with a lot less hassle.
hi Scott, your render looks nice 
…like pkolbo_pop said, keep an eye on the subdivs too.
As you can see, not the min/max reduces the blotchynes, it makes it finer but not less…
Your subdivs are set by 40, thats realy too low. While increasing the subdivs, the blotchyness fades more and more out. It needs more pre-calculation time, but it´s the way…
Out of curiosity, have you considered just using Brute Force/Light Cache? It’s very quick these days…
This is because it’s calculated on “screen units” rather than “world units”, and is thus resolution dependant. Try brute force and see if you notice a significant difference in render times.
Brute force should fix it for you. I knew subdiv samples also solves this, but when I recreated that small model, 40 worked. Glad to know that I haven’t been wasting my time setting those high.
Smalerbi, One other thought I had; how are you simulating the sky lighting? Is it the DefaultVraySky map that comes along with VRsun or an HDRI? I’ve seen HDRI’s causing issues like this, although I’d expect to see more of it…
…I can speak only for maya…but thee is a big difference between using HDRIs per environment or per domelight!
Domelight works much better in case of blotchys…
Ok…I will give it a try. I do not have much experience with Brute Force. Could you please share some settings?
Thanks…Scott
there aren’t many options for brute force, just turn it on. Its good for exteriors, gives you good quality with minimal problems. Only pitfall is it takes longer to render. How much longer is for you to do tests and compare.
With regards to Brute Force, I haven’t had much experience or luck with it. I seem to get a lot of GI noise. I know it’s because I have no idea what the settings need to be. Could you please share some BF settings to achieve the best results.
To answer the Sky question, it is the DefaultVRaySky map.
Thanks again…Scott.
Reduce ur adaptive amount as well in dmc, this helps IM to be consistent more than any other value that u fiddle with so far i believe. Go from 0.85 to .7 and see if there is any difference in the quality of ur gi. Or simply use BF+LC. In exteriors is the best combination.
Sometimes switching the Irradiance map interpolation and sample lookup method will reduce splotchiness. This is especially true when working with imported Revit or Rhino geometry. Try setting them to “Least Squares Fit” and “Overlapping.” These settings are lower than “Delone Triangulation” and “Density-Based” but will still produce professional quality results.
You can try Brute Force as suggested above but if you are working towards hard deadlines I would avoid it because it is not fast enough for complex scenes and hard deadlines.
Exterior with fine detail is oneway for bruteforce imo. IM is not that good anyways for very fine detail.
I was reading redshift manual, and in fact they do not recommend at all using IM on scenes with very fine detail. (RS is same as vray in terms of gi models and optimisation)
BF can handle ur scene much more accurate and probably faster eventually than IM. IM needs to use low adaptive threshold, high gi settings and detail enchancement for the blotchiness to go away thus high render times.
BF will give u better quality, equal times (maybe faster as well) and 0 settings to fiddle with.
Cheers