Self Illumination Photons 3dsmax Mental Ray

[ivanjay]

I followed a wonderful tutorial on cgarchitect which walks through creating a ceiling grid with 2 x 2 recessed lights built into the material. Traditionally, I was modeling all of this so this sames considerable time as all of my renders are interiors and most with a ceiling grid.

 

However, I get the notice that there are no photon emitters in the scene. Is there a way to make the A & D emit photons. If not, is it as simple as just placing a light just below or....? I rely on photons/GI to give me the great shadowing and depth.

 

I had read you can just crank up the final gather but my assumption is that will not produce the same quality renderings, what is your experience?

[pixelperfectg]

Is there a way to make the A & D emit photons.

Unfortunately, no.

 

If not, is it as simple as just placing a light just below

Yes.

[ivanjay]

Unfortunately, no.

 

Yes.

 

I did try that and it looks great. My next question is am I "doubling" the light to make this physically incorrect or should I not worry about that?

 

My thought is the self illumination throws off light as well as the physical light so this is truly accurate?

[pixelperfectg]

I did try that and it looks great. My next question is am I "doubling" the light

Yes, both are creating light but it's not a 1:1 doubling effect of the light because a mental ray self-illuminated material isn't as accurate as an actual photometric light source. I believe it even mentions this in the help file in one of the discussions about FG or self-illuminated A&D materials but I don't remember which off the top of my head.

 

If you use an actual light source below the self illuminated plane then you can simply disable the "Illuminates the Scene (when using FG)" option on the self-illuminated A&D material if the combination is putting out too much light for you but I'd still leave it self-illuminated to represent the visible light source.

[ivanjay]

Yes, both are creating light but it's not a 1:1 doubling effect of the light because a mental ray self-illuminated material isn't as accurate as an actual photometric light source. I believe it even mentions this in the help file in one of the discussions about FG or self-illuminated A&D materials but I don't remember which off the top of my head.

 

If you use an actual light source below the self illuminated plane then you can simply disable the "Illuminates the Scene (when using FG)" option on the self-illuminated A&D material if the combination is putting out too much light for you but I'd still leave it self-illuminated to represent the visible light source.

 

That makes sense. Thanks for your help!