Broken Area Light behavior in Maya Mental Ray.

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Old 03 March 2011   #1
Broken Area Light behavior in Maya Mental Ray.

Hi guys,

I'm encountering some weirdness with Mental Ray Area Lights at the moment, maybe some will be able to shed some light on that !

I did a scene with the following stuff :
  • Area Light
  • Area Portal Light
  • Emissive Plane
  • Ground

The different emitting objects (Area * Lights and Emissive Plane) have the same size and placed above the ground. The reference for me is the the Emissive Plane. Here are some renders now :

Scale 1.0 on emitting objects :

Emissive Plane


Area Portal Light


Area Light


Pretty much the same results, lets move on.

Scale 10 on emitting objects :

Emissive Plane


Area Portal Light


Area Light


Mmmhh Area Light doesn't react as I would expect, I do a quick brainstorming and decide to multiply the intensity by the square of scale (100) in this particular case and here is the picture :

Area Light Tweaked Intensity


Ok we are back in business Now I decide to try scaling down, See next post

KS
Attached Files
File Type: zip Portal_001.ma.zip (13.8 KB, 4 views)

Last edited by Kel Solaar : 03 March 2011 at 02:15 PM.
 
Old 03 March 2011   #2
Continuing the previous post :

Scale 0.1 on emitting objects :

Emissive Plane


Area Portal Light


Area Light


Area Light seems to do funky stuff again ... I divided my scale by 10 so I'm assuming it will follow the same behavior than when I scaled up, so I multiply my intensity by square of 0.1 (0.01) And here we go :

Area Light Intensity Tweak


Cool I don't see anything now ... Wtf? I decide to crank up the intensity a bit to see what's going on inputing 0.1:

Area Light Intensity Tweak Alternate


??? What's happening with the decay ? It seems to cover a larger area than expected.

So basically, has somebody a solution for this ? The problem I have with the portal light, is that it reacts to FG, and can't use a disc shape if I'm right. The scene is attached to the first post.

KS

Last edited by Kel Solaar : 03 March 2011 at 02:15 PM.
 
Old 03 March 2011   #3
Simply turn off the FG interaction in your Portal Light. If that's not good enough, use the miFinalGatherHide attribute on your Portal Light.
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Old 03 March 2011   #4
Thank you Sho,

I'll give a try at this, though my main concern is more about the Area Light itself

KS
 
Old 03 March 2011   #5
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