PDA

View Full Version : vray splotches, irradiance map, DMC question


LML
01-30-2012, 01:09 AM
hi all

I am struggling to get my head around something in VRAY and I'm hoping someone out there has the answer

I am rendering out a test scene in Maya and getting lots of blotches on broad wall and floor surfaces; these surfaces have only a generic vray mtl applied (no reflection, bump, etc).

I'm using IM and LC as my GI engines---I'm interested in perfecting a setup for animation.

So far, it seems to me the blotchiness is coming from the Irradiance Map (changing to Brute Force for the primary engine eliminates the problem).

The two ways that I've so far been able to fix it while still using Irradiance Map is by a) lowering the adaptive amount in the DMC sampler to something like 0.5 or b) increasing the subdiv's multiplier in the DMC sampler, to something like 4.0

Can anyone shed some light on what's going on? It seems like both of these are not ideal fixes. And further, I'm trying to figure out how DMC is tied to Irradiance Map--

Thanks very much!

LML

Darkmalan
01-30-2012, 06:20 AM
It does sound like the Irradiance map is what is causing the problem. The main way to reduce this problem would be to increase the Hsph subdivs value in the Irradiance map settings. I would increase this setting until the render time begins to be too long you can then begin to increase the interpolation samples which blurs the samples together. This will give a more uniform GI but will lose details in the GI if set too high.

Its a case of trying to find a good balance between these two settings. Hope this helps.
Kyle

Kzin
02-09-2012, 10:17 AM
hi all

I am struggling to get my head around something in VRAY and I'm hoping someone out there has the answer

I am rendering out a test scene in Maya and getting lots of blotches on broad wall and floor surfaces; these surfaces have only a generic vray mtl applied (no reflection, bump, etc).

I'm using IM and LC as my GI engines---I'm interested in perfecting a setup for animation.

So far, it seems to me the blotchiness is coming from the Irradiance Map (changing to Brute Force for the primary engine eliminates the problem).

The two ways that I've so far been able to fix it while still using Irradiance Map is by a) lowering the adaptive amount in the DMC sampler to something like 0.5 or b) increasing the subdiv's multiplier in the DMC sampler, to something like 4.0

Can anyone shed some light on what's going on? It seems like both of these are not ideal fixes. And further, I'm trying to figure out how DMC is tied to Irradiance Map--

Thanks very much!

LML

if your lighting contains primarely of indirect lighting, then you will have problems also with insanly high settings for irramap and lightcache. i had similar problems and found no solution. sure, you can increase the hemi samples, use a widther range for the 2 two rate values or more interpolation samples. but this will all increase your rendertime to a point there lightcache and irramap will make no sense anymore compared to brute force. and brute force is slow, really slow with alot of indirect light.

so my advice is to use well placed lights that bring in a lot of direct light. lights that fakes some sort of indirekt light, but this will help alot to reduce flicker.

ndeboar
02-10-2012, 09:22 AM
For production renders, I generally leave my dmc threshold around .02.

Brute force is your friend, i found Irradiance maps to blotchy in most cases. Brute force is really solid and doesnt flicker.

LML
02-10-2012, 04:20 PM
thanks all

ndeboar: so you put up with a bit more noise in this case I assume? a question about that, do you use the static noise, or the moving noise option (I think it might be "time dependent" in the settings)?

LML

CHRiTTeR
02-10-2012, 06:06 PM
when using irradiance map it is strongly advised to keep the time independant option checked (otherwise you'll get splotches jumping quite quickly)

When doing bruteforce, it depends on your own taste i think (which is the reason they added the possibility to turn it on/off)
For me personally, i kinda like to uncheck it sometimes (it depends really) it kinda simulated a filmgrainish look and it can look better to some ppl compared to static noise.

ndeboar
02-11-2012, 07:56 AM
im not a big fan of static grain, it looks like there is a stocking over the lens. Brute force is a bit noiser, but i generally find it an "acceptable" amount of noise.

CGTalk Moderation
02-11-2012, 07:56 AM
This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.