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View Full Version : Super ugly physical sun and sky renders. What am I missing here?


Freshfromthegrave
06-10-2010, 09:09 AM
Hey guys, I'm having some major trouble with getting good renders out of mental ray. I'm using the physical sun and sky nodes that come with mental ray (maya 8.5) and I've learnt a bit about the whole linear workflow thing. So of course my renders come out desaturated if I don't gamma correct my textures, the thing is when I do the gamma correction stuff the renders look even uglier than before and I can't quite figure out why. The shadows looks quite dark in places and everything looks very flat. It's almost as though mental is not bouncing any light but both final gather and global illumination are turned on (although I haven't turned on any photons since that seems to throw render times through the roof). I'm quite new to mental ray and coming from VRay (which I know very well) mental ray seems quite confusing to me...

Here's one of the ugly renders that come out of my current set up: http://picasaweb.google.com/109667798028322185874/CGTalkPosts#5481070297393815218

I hope you guys can see that, let me know if you can't. What am I missing here? :surprised

TaKIKO
06-10-2010, 02:09 PM
Do you have the lens shader on?

Freshfromthegrave
06-10-2010, 03:02 PM
hey takiko, yeah i do it's using the mia_simple_exposure lens shader with gamma set to 2.2 (it's all default), i did my gamma correction on the color textures only.

visua
06-10-2010, 03:22 PM
U are using GI but not shooting any photons, that's sort of contradictory is it not? ;)
Turn of GI, and use FG only instead, and change your diffuse bounces to 2 or more...

//NIC

Freshfromthegrave
06-10-2010, 03:53 PM
hey visua thanks for the reply :) when i turn the photons on (for the sun light?) it doesn't seem to make any difference o.O i found a checkbox for secondary diffuse bounces under final gathering options but no option to change the number of bounces, only reflections, refractions, max trace depth and a colour slider for secondary bounce scale. i noticed with a test scene that mental ray is bouncing light but it's extremely minimal, almost non existent judging by the colour bleeding. and with a sun sky system the colour bleeding completely disappears, although it did seem to be bouncing a tiny bit of light in the test scene (which was just a plane and some spheres in a new scene).

chafouin
06-10-2010, 04:02 PM
Can you post your scene? For me it looks like the FG is not activated.
GI and photons are a bit tricky, just turn them off for the moment.

And also which version of Maya are you using? There is a slider for Secondary Bounces in the Final Gather rendering options, but only since the 2008, maybe 2009 version. But if you can change Secondary Diffuse Scale color, I assume you have a recent version, with a Secondary Diffuse Bounces slider just below. Anyway, turning on secondary bounces won't fix your problem, it looks like you don't even have the primary ones :)

Autarkis
06-10-2010, 04:51 PM
If you've got an older version of maya ( pre-2010 i believe) type in select miDefaultOptions in the mel command window, and you should see the option to increase the FG bounce.

Also, try increasing the gain attribute of the sun and sky, it should brighten things up!

visua
06-10-2010, 04:55 PM
Or just miDef* (a tad shorter)

Autarkis
06-10-2010, 05:28 PM
true. :)

I guess i was just too lazy to type in a shortcut ... er.. that makes no sense.

Freshfromthegrave
06-10-2010, 06:06 PM
Can you post your scene? For me it looks like the FG is not activated.
GI and photons are a bit tricky, just turn them off for the moment.

And also which version of Maya are you using? There is a slider for Secondary Bounces in the Final Gather rendering options, but only since the 2008, maybe 2009 version. But if you can change Secondary Diffuse Scale color, I assume you have a recent version, with a Secondary Diffuse Bounces slider just below. Anyway, turning on secondary bounces won't fix your problem, it looks like you don't even have the primary ones :)

hey dot87 :) i'll try post a part of the scene tomorrow (btw how do i use attachments on the forum??) as i'm at home now and the scene files are at the office. i'm actually using maya 8.5... :surprised so there's no numerical slider for the bounces only the secondary diffuse scale color slider, which doesn't have a number just black to white and there's nothing else in the options :hmm: how do i enable the primary bounces? the final gather checkbox is on in the render globals. thanks for the reply btw :)

Freshfromthegrave
06-10-2010, 06:13 PM
If you've got an older version of maya ( pre-2010 i believe) type in select miDefaultOptions in the mel command window, and you should see the option to increase the FG bounce.

Also, try increasing the gain attribute of the sun and sky, it should brighten things up!

hey autarkis :) i'm using maya 8.5 complete actually :surprised i'll give that a bash tomorrow, although it's a bit strange they didn't put the bounce options in a more obvious place =\ i've also tried messing around with the mia_simple_exposure node controls but i wasn't able to get anything substantially better but i will try again tomorrow though :)

Or just miDef* (a tad shorter)

thanks for putting up with the mental ray noob guys i appreciate the help :) i kind of stuck with vray since the beginning :P i'll post again tomorrow morning and let everyone know whats happening!

Autarkis
06-10-2010, 06:13 PM
You will discover the Mental Ray implementation in maya is well... incomplete. Its always a challenge to make things you know are in there actually work the way that you want. Its getting better ( kinda :argh: )

Try just raising your gain, it should definitely make a difference in your scene. There's a quite complete topic in the help file about the sun and sky and mia_exposure node you might want to look at to know exactly how all the exposure attribute really work.

Good luck and let us know how that works out for you tomorrow!

Freshfromthegrave
06-11-2010, 01:28 PM
You will discover the Mental Ray implementation in maya is well... incomplete. Its always a challenge to make things you know are in there actually work the way that you want. Its getting better ( kinda :argh: )

Try just raising your gain, it should definitely make a difference in your scene. There's a quite complete topic in the help file about the sun and sky and mia_exposure node you might want to look at to know exactly how all the exposure attribute really work.

Good luck and let us know how that works out for you tomorrow!

yeah i'm noticing that more and more about mental ray for maya -.- thankfully my boss is not as opposed to the idea of switching software as i thought he would be!

ok so i've attached (tried to attach?) a light test of a piece of the scene. the main issues are that the wood is quite dark and the shadows in particular are very dark. now i redid this scene in Vray in max and managed to get a similar result, although the wood was a bit brighter, about the same as the texture itself. the easy fix for the shadows was increasing the brightness of the environment. now i can't seem to figure out how to do that with a sun/sky setup in maya =\ the exposure controls in mia_simple_exposure node tend to do funny things like desaturating the image and such. i did a bit learning with regards to GI and FG and i think i understand those now, but what happens with this scene is that when i turn FG on after doing my GI and photons is that all the light bouncing from the blue plane disappear and even after blowing the photon intensity right up to their maximum (!!!) they still don't quite come back... ok so what am i doing wrong here? xD oh and i couldn't get to those mental ray default options for some reason? but none the less i think someone else said that it wouldn't help me because it looked like the primary ones were off anyways xD

*EDIT - ok i forget the textures lol... i uploaded the best i could! still gives the general colour of the wood :)

chafouin
06-11-2010, 05:18 PM
I didn't try with you textures, I just had a quick look at your file and I already saw something that may solve your problem : your Final Gather Map is set to Rebuild Freeze. Put it to Rebuild On for the moment. Freeze is useful for animation, and only when your scene is almost final (model, camera position, etc).

Hope it will fix your problem.

Freshfromthegrave
06-15-2010, 05:41 PM
hey guys sorry for the long delay, i've semi sorted it out though :) it seemed to be a combination of a lot of things like the shaders and textures (the colour of the wood just looked ugly under sunlight) and honestly i'm not sure what i did with my lighting settings but they work better now xD so it's looking like something now and the director was happy so i can stress less now :) thanks for your replies guys! also dot87 i think that whole freezing map thing just has to do with opening it on a newer version of maya, it was turned on in my 2009 at home and it was set to rebuild on 8.5 at home :)

EdoAlf
12-28-2010, 07:52 PM
There's a weird issue I've been experiencing in both maya 2010 and 2011 regarding physical sun /sky. When I'm working on my scene, even having test rendered a few frames and having everything looking good, it reaches a point when, for no apparent reason, the renders start looking just like yours, very flat and with hard shadows. The only solution I've found is to delete the physical sun/sky node completely, creating another one and setting it up all over again from scratch... then it works great again until it happens again. Any ideas?

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