View Full Version : Need Help with objects casting light

05 May 2009, 06:25 AM
My scene is a hallway, and ive modelled the geometry etc, and now im onto the lighting.

The light sources wont be seen directly from the camera, as the geometry has it hidden. For the actual light source, ive modeled simple geometry where the light source is, and this is the object that i will assign the cast light/glow etc to.

So that being said, i saw a tutorial in my searches that enables one to use an architectural shader to glow, and with GI it did a pretty similar thing for what i want.

However that tutorial was for max and im using maya 9, and i just wasnt able to 'port' the process over, i think im still too new for that.

so my direct questions to you would be:
1. How do i get an object to emmit light
2. How to i use the above object to emmit photons (like i would with a spotlight) to create realistic lighting
3. If at all possable how would i make the light emmiting object transparent to the camera, while still being a 'light'

any information is welcome, or even tutorials that pertain to the subject


Edit: this is the tutorial that i couldnt make work in maya:

Material Tutorial: Glowing Material with Mental Ray

05 May 2009, 08:13 AM
If you have vray there's some sort of vraylight material. Honestly though, while it works, there's more efficient ways of getting an object to "cast" light. The FG method, in my opinion, is very hacky and expensive. I do believe it's easier in max with the light material.

Over at mymentalray there's some vertex painting stuff for lights, but, again, it's very time expensive.

05 May 2009, 10:21 AM
I'm not good with Maya, but this is how I achieve it:

1 & 2) Switch your renderer to mental ray, turn on FG. Assign a mia_material to your object, then set your light color under Additional > Additional Color. Control the intensity by increase value, can input >2.

2) Select your object, go to Window > Attribute Editor > Render stat > untick Primary Visibility.

05 May 2009, 01:40 PM
Thanks for the replys!!

What i ended up going with was a surface shader with a slight glow on it, and then an area light of the same shape just infront.

im still a ways off from what i want, but this is a step in the right direction

heres what it looks like so far

Edit: where the 'consol' connects to the wall, see how it kinda glows there where the photons seem to be hanging out.... how would one cut down on that? or is that something ill have to to in post?

05 May 2009, 06:59 PM
Tweak your accuracy, radius, and FG rays to get rid of the bleeding.

05 May 2009, 08:18 PM
those attributes would be found in the render options yes?

also, for those values, can you give me a direction that i can expect things to go?

ie, more rays = softer etc


05 May 2009, 11:15 PM
Yea its a tweakfest to get them both optimized and smooth.

I start with GI, with the radius around 20 (depending on the scale of your scene). Put the accuracy at 100, render. 200, render. 500, render. Go till there's no noticeable difference. Then, tweak the radius until there's no noticeable difference.

Once you turn the GI on, things should really smooth out. You can even bring the number of photons down a notch as the FG solution melts the photons together. Depending on your Maya version, there's either an accuracy setting, or a Rays setting. I don't know for sure, but I think they're the same thing. Raising that number increases the quality, but time increases with it. FG settings can be pretty in depth, so I'd suggest looking up a tutorial geared towards just that.

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05 May 2009, 11:15 PM
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