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CurtJ
07-09-2007, 06:05 PM
I've been lurking around this forum long enough, about time I joined - Hi all!

I have a question which I hope somebody may be able to help me with...

I've been using Maya for quite some time now, but never really pushed the boat out when it comes to lighting and texturing.

I'm trying to prepare a realistic light and shader setup to model a platinum ring (which I'll probably be asking more about later)

Being familiar with the Maya renderer, and feeling that it's not favourite for the job, I've decided that using Mental Ray's Image Based Lighting with Final Gather & Global Illumination will provide me with the best results.

I'm completely unfamiliar with Mental Ray, but have what seems like a good reference book (Lee Lanier -- Advanced Texturing & Lighting), and I'm slowly getting there with the platinum look, although it's very much a case of two steps forward, one step back... I'm getting there though.

Something has taken me by surprise, and I'm hoping someone can explain what's happening.

I was using IBL with a HDR image file, fiddling about with it, then I added a directional light to my scene, default settings, and it for some reason it's made the scene darker:

http://www.curtjackson.co.uk/img/ibl_dl_diff.jpg

Left hand side - IBL only, right hand side - added directional light.


Can anyone explain why this is happening, as I prefer the darker version, but don't know how to control it. I've even turned off all the light's features - intensity, Illuminate by default, both emission types, and shadows, but it still affects the scene. Only if I delete it does it revert to the lighter version.

What's happening here?.. Can anyone tell me?

Any help much appreciated.

Curt.
MikeBracken
07-10-2007, 04:29 AM
Just a stab...Im a max user...in max this queston has come up a few times. The default lights
are on in max until you creat a light. Then they are turned off. Not sure if this helps, but it
was the fist thing to come to mind.

Regards,
Mike
MinaRagaie
07-10-2007, 08:01 AM
Just a stab...Im a max user...in max this queston has come up a few times. The default lights
are on in max until you creat a light. Then they are turned off. Not sure if this helps, but it
was the fist thing to come to mind.

Regards,
Mike

Second that...
I'm a maya user... and the exact same thing happens with maya. It adds "Default Lights" when there are no lights in the scene. if you're using an IBL node that isn't considered a light. once you add a light the defaults lights are removed.

Go to Render settings >>>Common Tab >>>Render Options >>>uncheck "Enable Default Light"
that way you'll see what your IBL node is really doing to your scene...
It will definetly get darker... so you might wanna boost the FG "Scale" or the color Gain of your "HDR"

Hope this helps :)

-Mina
CurtJ
07-10-2007, 08:31 AM
Of course, that makes perfect sense. It didn't even cross my mind though - I was assuming the IBL node had overridden the default light. I'll check it out later on.
Thanks guys - appreciated.


Curt.
noizFACTORY
07-13-2007, 02:30 PM
Curt, its always advisable to turn any default lights off before starting to light a scene, irrespective of any package you are using.
CurtJ
07-14-2007, 02:08 PM
Thanks all - you were right, it was the default light being brighter than the light I added.

I usually add a light before any rendering, but I thought IBL would cancel it out like a normal light does - it doesn't. Also, I'll see if I can disable maya's default light as standard.

Thanks again.

Curt.
gerardo
07-17-2007, 12:38 AM
You may find Smart IBL (http://forums.cgsociety.org/showthread.php?f=21&t=519057) interesting.



Gerardo
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07-17-2007, 12:38 AM
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