View Full Version : Light Source Question

09 September 2010, 04:02 PM
Hi Guys,

In Max, I have a simple flourescent lightbox in my scene. Would it be best to either self-illuminate the light surface to illuminate the scene or place a rectangular-shaped light? I'm rendering in Mental Ray.

My gut says use a light, but wanted to know what you thought.


09 September 2010, 10:24 PM
My gut says use a light, but wanted to know what you thought.I'd say use a light because:

Trying to illuminate a scene with self-illuminated planes with FG will more than likely require higher FG settings than you'd need with a typical light source.
Self-illuminated planes will not provide the direct light that a typical light source provides.
Self-illuminated planes do not emit photons therefore GI and/or caustics will not work with a typical GI and/or FG scene.
This is an 'iffy' one...Self-illuminated planes will not produce the specular (fake highlight) option that lights have. Of course this would only be an issue if you need a specular light source and I realize you may not.

Now, the downside to using a light source instead of self-illuminated geometry? Well, unfortunately all the area lights used in mental ray for 3ds Max emit from a center point instead of evenly across the area dimensions of the light source.

Some area lights are better than others in this regard but they all exhibit this behavior to some degree. That can be a royal pain in the @ss if you need to create a large smooth area light in 3ds Max with mental ray. There are some hacks (light shaders) to assist with this issue, but that's a whole other ball of wax.

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09 September 2010, 10:24 PM
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