Why am I having this error with FG+GI?

[Houkah]

Looks like that weird banding you get from depth map shadows. I had the same problem and just upped the resolution of the depth map shadows and changed the depth map bias. I don't know if you're deriving the settings from Maya or not. Look in your light attributes.

[Dark Alchemist]

no shadows are on. dmap and raytrace are off for shadows so that can't be it, could it?

[Houkah]

no shadows? I have no idea then. Sorry I couldn't be more help.

[alexx]

try tweaking the radii from GI and especially FG..
set the min and max lower..

maybe you can post your fg and gi settings..

cheers
alexx

[Dark Alchemist]

I thought I did post in that link. If I need more info I can grab for you cause I am at a loss. I tried all sorts of settings.

[Jozvex]

I'd suggest give the GI a radius of 1 or 2 and upping the FG samples to at least 500.

[Dark Alchemist]

I will try the gi part as for the fg I still have the problem at 1000 even :/

Leave the minimum at .5 and max of 5 for FG?

I did as you said and the rippling is still there (I can see it through the bright room..room got very bright).

[Dark Alchemist]

Anyone else know why this is happening?

[stunndman]

i think you should take a look at the GI and FG tutorials at AW's site - using 1000000 photons for this scene is definitely an overkill - the tutorials are quite short and will be a good guide on how to start tuning your settings

[luminis]

Try the following things:

Increase the Global Illumination accuracy to the maximum setting.

Set the Global Illumination Radius to a small, but nonzero value (Perhaps 1.0 or smaller). If I'm not mistaken, a value of 0 will make mental ray calculate the most appropriate value, which is not always the best.

Decrease the number of photons emitted, 1000000 is just too much for a scene of this size, a value of around 50,000 should yield decent enough results.

Render again, and if it still gives you those problems, increase the Photon Volume accuracy, and set the Photon Volume radius to a small, but nonzero value as well.

The Final Gather settings look alright as they are.

Let us know how it goes.

[Jozvex]

I'm not sure, but I thought that the Volume Photon settings were only used when rendering things like Volume Caustics?

[Dark Alchemist]

Trust me I went from 1k to 10k to 100k to 1m and it stayed that way. Please, remember I said those settings were at the max I tried and still I got the garbage areas which is just weird.

I am rerendering with the recomendations though and will report the findings.

[Dark Alchemist]

I did all of your suggestions and all it did was become brighter and the errors more noticable.

Here is the scene maybe one of you can take a whack at it and see what I did wrong (the scene is the one you see not the one with everyones suggestions).

Thanks.

The Scene (http://Mysticglow.com/testingfg+gi.mb)

[Nick2970]

This has nothing to do with your GI/FG settings, trust me, Change your sampling to Guassian and turn jitter on, looks like you are using box at the moment, let me know how this goes.

Cheers, Nick

[Nick2970]

My apologies, I didn't see you had posted your settings, I think it might be your GI/Photon radius, read this tutorial it is brilliant!!

http://www.3dluvr.com/intercepto/maya/tutorials/mray_thegathering/indoor02.htm

Cheers, Nick

[Dark Alchemist]

Well, I give up on the scene. I tried those settings last night and same deal. I have no idea what those lines are but all I know is every setting I have tried comes up with that error.

Thanks everyone for your help and suggestions but some things just can't be figured out (although I will touch it every now and again in hopes I stumble onto the problem).

[Carina]

If you don't use FG does it still happen?

Cause when I use GI only at low GI radius, I get banding where surfaces go from light to dark. The more I up the radius the less it's visible. For example, using a radius of 10 it is completely gone.

I would try to figure it out though, cause if you get that kind of a problem with such a simple scene, you will only run into it again;)

[Undseth]

First I wrote;
"My guess is that the FG min-radius is set too high."

But now after experencing a very similar issue with mentalray, I found out that; it will be corrected by lowering the MAX radius.

I increased the number of FG rays, but that didn't help.
I lowered the MIN radius very much, but that didn't help either.
So I lowered the MAX radius and then it smoothed out.

I hope this helps!

[Dark Alchemist]

That did the trick on the ripples now I am trying to ferret out why the rest of the picture has color splotches.

I used .03 and 0 (settled for .001) for min and .3 on max for FG and the bands went away and used 250 for the FG rays.

I upped to 1024 and still had splotches but not as pronounced. So, I am currently rendering at 2048 and the time its taking is horrible but I will report back.

The next test at .03 min .3 max. (http://Mysticglow.com/whatsthis-3.jpg)

It just now finished rendering since I posted the original reply. 2048 and the render time grew hugely. Notice the errors now around the corners of the cube so I can't win for losing. :/

The next test at .001 min .3 max 2048 FG Rays. (http://Mysticglow.com/whatsthis-4.jpg)

[Carina]

What happens to the blotches if you up it even more? the radius i mean.

[luminis]

Originally posted by Dark Alchemist
...now I am trying to ferret out why the rest of the picture has color splotches.[/URL]

I'm quite sure that the problem with those color spots is due to the GI settings.

The GI Radius seems to be good enough, as the artifacts that are introduced by a bad radius are not seen - but its still a good idea to tweak it somewhat to see its effects. The problem could also be a lack of photons. Try to increase the number of photons emitted. My guess would be to use 3 to 4 times as many photons as you are using now. (Are you still using 1,000,000? If so, it would be very strange that you still see those color spots, and if that is the case, do not increase the number any more, just fiddle around with the radius). When you increase the number of photons, you can also increase slightly the GI Radius, to help it look better.

[stunndman]

i tuned the scene a little - it rendered in 7 minutes - 5000 GI photons - accuracy 1024 - gi radius 22 - 300 FG rays - FG 0/.35 - it's a start

http://212.186.161.160/shared/DarkAlchemistFGGI.jpg

[Dark Alchemist]

I had to run off to work and just got back home and read this. Now my next scene had some of those settings about equal to that but on a 700mhz machine I never could get it to finish rendering before I had to leave.

I am still tweaking but from my findings so far I settled for 20 on the gi radius and it helped the blotches.

I will report back (I can't wait until end of May and I get my XP 3500+ barton core or the p4 ht).

BTW: Should it be this hard for such a simple scene? Scares me for future work with a complex scene. Already tons of hours in tweaking which, to me, means something is not right in MRay's algorithm

[Ryan8311]

I think I discovered the problem. I was having the exact same problem, but then I read a tutorial that was discussing making a light and setting its intensity to "0" just so the renderer wouldnt add a default light as it does when you dont add any lights to the scene. Try doing this, then use FG. In my test, it seems to have solved the problem. Also, use these settings for MR:

FG Settings:

FG Rays: 500
Min. Radius: 0.3
Max. Radius: 8.0

Sampling Quality:

Min. Samples: 0
Max. Samples: 2
Jitter: Enabled
Filter: Gauss

Let me know if that does it for ya.

[Dark Alchemist]

I pulled the old scene out and now I have a 2.2ghz core speed (2700+ overclocked) Athlon and it still renders slow BUT I did try your settings and the answer is no. Mental Ray hates the scene for some reason. Not even using the hidden menu for FG features worked and this is not the first scene I have had issues with when dealing with FG+GI.

[rock]

Alchemist,

Try to play with these 4 Mental Ray tutorials (2 indoors, 1 outdoor, and 1 hdri lighting), as Nick suggested.

http://www.3dluvr.com/intercepto/maya/tutorials/mray_thegathering/indoor01.htm

[Dark Alchemist]

I played with those for quite some time and I finally got it to work but never ever 100% (if you zoom in on it you will still see the errors) but thank you.

What I did do to minimize the error was modify these settings:

Glob Illum Accuracy: 500
rest default

FG Rays: 500
Min Radius: 6.117
Max Radius: 13.797

Min Samples: 2
Max Samples: 3
Jitter: On
Filter: Mitchell (I hate the washed out look of Gauss but no difference on the rippling)
Width & Height: 4.00 & 4.00

Light Attributes:

Photonic Energy: 12000, 12000, 12000
Exponent: 1.34
Global Illum Photons: 100000 or 1million if speed is not an issue

This helped immensely but as I said its never 100% :hmm:

[CGTalk Moderation]

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.