View Full Version : Light without GI or FG

08 August 2009, 08:11 AM
I was just wondering do you people think that the Maya mental ray Physical sun and sky is a good option for rendering outdoor scenes. I mean it gives good results but at the same time it just looks almost always the same and there is not a lot to tweak. On the top of it it uses FG which complicates the things even more.. I was just wondering do you know some tricks or rigs that can fake sunlight or give me a point to a decent more tweakable solution.I am not asking for a particular project of mine. I am just trying to gather as much info a s possibleand try a lot of techniques. BTW Is there a good was to actually represent daylight situation without FG. I was looking ot the Gnomonology light rig. It gives good results but the result is not what I need. I just want to know how it works and since they dont actually provide a breakdown PDF but just the rig I was hopping that someone here can give me a cople of tips on lightining without the use of simulated diffuse light suck as GI and FG. Any help GREATLY appreciated

08 August 2009, 09:48 AM
Why don't you go for image based maximum exterior scenes lighting are being done with the help of hdri's.........

08 August 2009, 10:23 AM
yeas and the most time consuming ones. besides that for proper IBL you just NEED Final gather as it is responsible to extract radiance from the HDR values... wee you can youse it to get only cool reflections but this is not lighting... so.. this is not the thing I am asking

08 August 2009, 01:08 PM
What do the Gurus think about all that ?!?

08 August 2009, 05:51 PM
Ok, I know I am kind of impatient but isnt there anyone who can give me some kind of advice ?!?

08 August 2009, 01:41 AM
If there was a fast, easy to use and good looking alternative to final gather, don't you think it would be more commonly used? :rolleyes:

Sure you could use a blue tinted light opposing the sun to get some color in the shaded areas and add ambient occlusion to get some depth. But other than that there aren't many workarounds if you want a global illumination look, at least none that would be faster than FG.

In my experience MR's sun and sky is fine for what it does. Throw a different sky in the background and it looks great in most cases.

08 August 2009, 09:45 AM
Have you tried those scripts generating a dome of light that have been around for a while now before people switched to FG?
Here is a good one: Illuminati (

08 August 2009, 04:33 PM
I looked at the script it is pretty cool and nails some pretty good results. To my questions I am gonna attach a image too. ( it is just an experiment)... Here are two images the first one is with FG turned on and the second is OFF. As you can see the firs result is much nicer. Any ideas on how to fake that without the use of FG. The other thing is that I cant figure out why are these spots occuring. Thi happen only when I am using area light for the windows WITH attached Physical light shader for them. Any ideas on my problems?

08 August 2009, 04:37 PM
Huh? I thought this was about sunlight?

Anyway, to fake GI in the pictures you posted, just place some weak lights (with shadows turned off) in the areas where you want some light spill and bounce.

Sure the traditional way of lighting has its place and I prefer using it myself on many scenes... but if a FG look is specifically what you're after, why not use FG??

The spots are simply because your FG settings are wrong for the scene. Maybe you should just learn to work with FG instead of spending time to find workarounds for a perfectly capable solution...

08 August 2009, 04:50 PM
well thank you for the tips about the lights but instead of just saying that my fg settings are wrong for the scene can you point me to the right ones. after all the image clearly speaks that i am not doing something right..but not telling me exactly what and thats why I am posting here...

08 August 2009, 04:56 PM
No. I cannot tell you what's wrong with your settings because

a) I don't know what your current settings are.
b) It's different for every scene.

Try troubleshooting the final gather yourself and learn something along the way instead of expecting people to spoon-feed you. :shrug:

08 August 2009, 07:59 PM
i see you are one of those that knows a lot but think that is too precious to be shared. ok i will figure it out ;)

08 August 2009, 08:13 PM
I wouldn't be posting here if I wasn't interested in helping out. But if you expect help you'll have to cooperate, give us some information to work with and carry part of the weight yourself.

What you're doing is liking posting a photo of your car and saying "It's broken. Tell me how to fix it."

08 August 2009, 08:22 PM
the number of points interpolated is too low, or the radious of interpolation is too low (you can use only one of this methods), you will lose contrast though.


the number of final gather points is too low, will take longer but you wont lose contrast

08 August 2009, 08:36 PM
Stefan, You are right.. sory about that.. So basically my setup is the following. I have area light on the windows (mr area shape enabled with 2 samples) To each one of them I have a physical light attached... I am shooting 100 rays. Tried raising that but the e spots dont dissapear just the rendertime increases dramatically. Tried increasing density. There are points again just smaller in size... Tried increasing the point interpolation.. it just doesnt affect the things a lot.. So I did that before posting.. I dont know what is the problem. I am attaching a current render with the settings that I have now :)

08 August 2009, 12:00 AM
well I posted the settings..

08 August 2009, 12:22 AM
Are you using GI here? What for? Just place some area lights where the most of GI reflects, mimicking the GI looks by using the reference frame.
If you have problems with noise, try the following: don't do the complete black environment, but light it slightly with a gray moonlight, and then darken it in post. See if it fixes the noise problem.

08 August 2009, 12:40 AM
i am using final gather. about the placing of area lights to mimck the GI look. what exatly are you suggesting to do. polace a couple of rectangular area lights facing the windows with color tinted to warm yeallow. can you givem e some more insight to trying to replicate the GI andFG look using only traditional light. That would be extremely helpful for me. Sory if i am asking stupid uestions...

08 August 2009, 01:00 AM
The lights must be positioned where the surfaces reflect the light, to mimick its look.
Area lights are totally fine in my opinion, unless you are about a very serious optimisation. If you need a serious optimisation, you can use spotlights with shadowmaps, though shadowmaps may eat your ram if there are a lot of.
First render with GI. Save the image. Use it as a reference.
Lookwhere the areas of the most bright light reflections are. If needed, make the light mimicking GI to ignore the object from which it reflects the light from, so you can place it incide that object without it casting shadows.
Tweak the color, position and intensity to match the GI reference.

08 August 2009, 11:56 AM
well I posted the settings..Dude... you sure are impatient. Please remember that this is a free support forum and our lives don't revolve around answering your questions. If it's that important to you call Autodesk.

Anyway, if you still want to render this scene with FG and not follow the good advice given by mister3d, here's some tips:
- You can use way lower settings such as Accuracy 25 Point Density 0.025 for testing.
- Add moon light and street lights to your scene. FG alone doesn't look that great usually. Extra lights coming from the direction of the camera will smooth the spots out.
- Textures will also help mask any spots by blending the noise.
- Are you using area-lights in the windows? If not do so and make them fill the entire frame.

Hope that helps...

08 August 2009, 01:57 PM
Stefan: You are right sory about that :) All of you are very helpful to me and I dont want to annoy anyone.
Anyway. As far as the FG is concerned. I did the diagnose and it happens that there are some strange clusters of points far apart from each other exactly on the places where the spots are located. Yes, I m using area lights with attached phys light shader for the windows. This is my last result

As far as the light without FG I tried some setups and different placement of the lifgts and the best I did is this... where I use the are lights for the windows again.. a very weak spot with MR shape enabled ( rectangular) using some raytraced shadows... I guess to light without FG just take practice and practice and is much harder but deffinately more rewarding and trouble free..

08 August 2009, 02:05 PM
Stefan, is it normal for the spots to become that HUGE when I lowerthe settings as you suggested for testing purposes ?!?

08 August 2009, 08:57 PM
You need to heighten the FG precision. You will need a lot of rays as the scene is very dark. (

You can tee the fake GI setup. It took me 3 and half minutes to render an HD frame, without any noise. With FG it would take an hour minimum to only approach the same result. And there will still be some noise. With shadownaps I gues the rendertime could be cut to 30 seconds or something. Sure there are some differences, but they could be eliminated, I just a bit lazy to do it. (

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