Irradiance map problem.

[joecharon]

Hi. Does anybody know what is wrong with
my irradiance map? It is very grainy even with
high setting and it produces useless outputs...

[Codi]

The irradiance settings look fine to me, but those black splotches on the precalc image are weird, how is the scene illuminated (VRaySky, HDR, ..)? Are you using an SkyDome or are you lighting with an environment map? Which settings do you have on the DMC sampler settings?

[joecharon]

The scene is lit by sky dome. I realized that this
problem is not scene specific. At the first image
is same scene rendered with light cache/brute force.
Problem started today. In the morning my irradiance
maps were looking OK. I have rendered other scene
and as you can see irradiance map is very grainy too.
On the third image is correct look of arradiance map.
I have reinstalled Vray but without success...

[ene.xis]

check ur dmc sampler noise treshold, and increase the irmap interpolation samples, see if that helps.
Nevertheless there seems to be not enough light samples coming in...
but its dificult to judge from that info.

[Codi]

So you are using an HDR image in the texture slot of a VRayLight set in Dome mode to get the global illumination?

Have you changed the default DMC (QMC) Sampler settings?

If you are using an HDR make sure you are using the correct mapping for it, in the VRayHDRI map check if you have it set to angular, spherical ... if it's not correctly mapped it can produce splotches.

[joecharon]

There is no HDR. Just Skydome.
Strange... Now it seems to be OK againg.
But still with grainy irradiance.

[Codi]

You can try to increase the dome subdivisions. If you have checked 'store with irradiance map' try 100 otherwise 20-30 should be ok.

Post your DMC Sampler settings. As ene.xis said, if noise threshold is too high it can produce splotches too.

[dlparisi]

I tend to get this problem a lot on interiors that are lit mainly by smallish windows into a large space. I usually just up the Irr. map samples to ~100/50 and it clears it up. I really don't know what's causing it though so these seatings may just be overkill when a quicker tweak somewhere else (maybe the DMC noise) could clear it up.

[samuel_bubat]

I would think you have to much samples. In my opinion the default presets (medium/high/.. etc...)
are not optimal for High dynamic situations like Skydome, Vray/IES Sun or overbright lights.
I also do a lot of interiors and usually I have to tweak the tresholds by myself to get decent rendertimes and clean images.

Here is an example how a scene comes out with medium settings (like you posted above)
(show samples on, Vray Sun/Sky, Log. Exposure)




This is how a custom tweaked Irrmap turns out. Imo this is how a sample distribution should
look like. Few samples in regions like walls.. where not much indirect shadows are
happening. And much samples in regions like corners.



I used the following settings to get this distribution. You can give it a try, but it may
vary from the dynamic range of your scene as well as other factors. Play with the
tresholds to get a similar distribution like i used.



The final image.....



Hope that helps,

cheers,

sam

[joecharon]

Thanks for your settings Sam, they produce nice outputs.
Here are some new assignments:
Irradiance map works fine with light cache. You can see it
in the image1.
With brute force as secondary engine it looks like in the
image2.
My DMC image sampler is set to min/max 1/30,
DMC sampler has adaptive 1 and noise tresh. 0,01
in both images.
In the image3 there is result of irradiance/brute force.
Brute force as secondary engine is set to 8/3.
In the image4 there is result of irradiance/light cache.

Now what is my aim. I want to produce an animation
of this interior with camera rotated 360°. For better
quality of animation i wanted to follow this animation
workflow which is different from that in Vray tutorials:

http://asgvis.com/index.php?option=c...d=37&Itemid=57

I think it is more applicable for this kind of scene than
irradiance/light cache method.

Now it is a big problem for me - i can't use
irradiance/brute force method because of irradiance
strange behaviour and irradiance/light cache produce
too big shadow leaks as you can see in the image4.

Now. Does anybody know how to solve this?

JP