light glows and optical FX in mental ray

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Old 02 February 2013   #1
light glows and optical FX in mental ray

I am rendering with Mental Ray and I'm trying to find a way to make lights glow and even create opticalFX like lens flares. I can do this with the Maya software render but I haven't been able to find a way to do it with Mental Ray. Also I don't want to render out elements to achieve the effect in the composite, I would like to try and do it all within the render.
Can anyone suggest how I can achieve this with mental ray?

Thanks in advance.
Old 02 February 2013   #2
For light glow, use the mia_Surface_Light shader. Or maybe it's called Light_Surface. Either way, attach this to the Additional Color slot of your mia_material_x, and then you can emit FG light or regular light from the geometry directly.

I use this shader for all my light bulbs in my interior arch/viz scene, and also for all the light shades in my fixtures too. That is, a spherical area light inside the bulb geometry, a Surface Light for the bulb geometry, and another surface light for the light fixture's glass geometry as well. This way you have three controls minimum, two on the shader level and one as a photon-casting actual area light as well.

Here's an example:

You can also map the Surface Light to its own shader, to control how the light "casts" if you like:

But at the end of the day, you're going to want to do any actual "glow" from objects or lights in post (compositing software). It's vastly faster, you have more control, and you can quickly fix problems this way. There's no reason to be a purist or "do it all in one render". Use as many tools as you need to get the job done as efficiently as possible!
Commodore 64 @ 1MHz
1541 Floppy Drive

"Like stone we battle the wind... Beat down and strangle the rains..."
Old 02 February 2013   #3
Thanks for the advice InfernalDarkness. Nice job with the bathroom render, it looks really good.

The "Surface_Light_Shader" is a good one and I have been using it, but I am also trying to get the lights to "ping or flare" for lack of a better word. Kind of like when a car head light is caught in the camera, there is a little horizontal flare as well. Would this be a camera shader?
I can do it with the Maya software render but I would have to render that as a separate pass and comp. I might try to use the render layers, so I can render with maya software and also mental ray.
I want to avoid comping. I want to see how close I can get just with in maya.
Old 02 February 2013   #4
Those effects should be done in post. I understand your intention, but there's no reason for doing these inside Maya. What you'll spend in rendertime you'll lose in your life, as in... it's not efficient and a great waste of time. It can take just a few seconds in Photoshop, Nuke, or After Effects. Or you can waste hours of test-renders trying to "get it right", and then have to do it all over again for another scene.

The effects that you're using in Maya software are kinda fun, but far from photorealistic. For example, the glow will not show up in raytraced reflections. Not that it would in postwork either, but it's kind of a fruitless endeavor to spend rendertime on it.

But do what you like!
Commodore 64 @ 1MHz
1541 Floppy Drive

"Like stone we battle the wind... Beat down and strangle the rains..."
Old 02 February 2013   #5
There was a glare shader that you put in the camera and gives glow. But they don't have anymore in maya, only softimage has.
But as Infernal said the thing takes too long to put glare, like rendering the image twice.
Old 02 February 2013   #6
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