Mental ray and glass

[paulwicke]

Hi all, my names Paul and Im from canberra australia. Im currently doing some visualisation work for a client and im at the point of rendering an interior shot of a building. For the exterior i just used physical sky and sun and that was fine but now i find that the interior is just not getting enough light in now ive popped a portal light in just behind the window but it doesnt seem to be making a difference but if i take off GI and remove the portal light i start getting more light in plus nice shadows but soon as GI is turned back on the light is reduced and the shadows are gone. I get the feeling that the glass material i have for the windows is blocking out light-does GI require a MR material for glass to work properly? Im currently using a blinn material with fall off reflections and 100% transparency, am i correct in thinking that this is my problem with GI?

Sorry about the novel of a post for my first post.

[Justin Hunt]

As to the workflow in Maya I cant help but there are a few ways round this

 

It should be possible to do in Maya, but in max in the object properties-> mentalray tab you can set the object to be invisible (pass through) to FG and be excluded to emit photons.

 

or

 

Hide the glass object, create and save the Photon and FG maps, freeze them. Unhide the glass and re-render.

 

or

 

Try moving the portal light into the room, ie in front of the glass.

 

jhv

[paulwicke]

woah quick reply.

Thanks Justin ill give those things a try, i think hiding it till after i make the FG and GI map is the best bet since i have to make them for the animation anyway. Thanks again

[prashanth]

hi,

 

Use the new 'MIA Shader' its physically accurate and they hav built in photon shaders, so the light will pass thro the glass without any hectic workaround..pls note that your refraction amount is set atleast to 6..

 

cheers

[mathes]

And make sure Thin Walled is clicked on for your mia_material, and that your windows are a single plane.

 

The reason you're seeing more light with GI off is because I assume you have multiple FG bounces turned on. GI reduces FG to one bounce.

 

You can also mess with your simple_exposure node to create more light. Upping your gain/knee will brighten the image..and blow out your windows, so there's a fine balance.