View Full Version : mr driving me up the wall! Trying to apply envportal shader to rectangular area light

12 December 2010, 06:04 PM
I'm using 3DS Max and keep getting the error message:

Shader 'mia_portal_light' must be applied to a VISIBLE rectangular area light to work correctly!

I've applied the shader to.... a rectangular area light.... and it's visible.

I've made a mr area spot into rectangle in Area Light Parameters and have plugged the shader into both light & photon emitter shader slots.

I've read a few posts on this and another forum and am not sure what's going on.

I'm using in conjunction with mr photographic exposure control.

Settings in Environment Portal:

multiplier 1
shadows on
emit direct photons.
transparency white

edit - I'm trying to use with GI, not FG.

12 December 2010, 07:37 PM
Why not just use the portal light type ?
You are describing the Maya workflow.
Are you needing to exclude things from the lights ?


12 December 2010, 10:06 PM
I received the same error message with the mr light portal so figured I was doing something wrong. Also my render was really dark too.

I'm reading lots of maya mr stuff and trying to apply it to Max, it's sometimes a bit tricky to work out whether the buttons/workflow is generic or not.

I was also reading the documentation that is in the Max\Help folder suggesting the workflow was to use a rectangular area light.

On CG architect people were describing that thay were gaining faster render times with the use of this particular light shader however I've only used this before in conjunction with FG. However I find I get much slower render times although the quality is better.

One thing I'm failing to do is use a mr light portal 'to focus GI photons' - which you can apparently do. I know how to use importons for this but I'm trying to suss out whether I'm missing a trick here with the light portal. I'm trying to master mental ray! What a bitch it is though!

Are you able to describe the steps I need to take use use Portals to improve GI?

12 December 2010, 11:14 PM
There is no special setup for the portals in Max. I use both Max and Maya at work, and the Max MR workflow is way better (IMHO). In Max all you do is create and place your portals. They will emit photons without any additional setup. If the portal is set to the default "Use existing Skylight" then all you need is to have the MR sky on. If it is set to "Use existing environment" then you just make sure you have an environment map set, and adjusted bright enough as well.

For custom you assign a shader/map yourself.

So, essentialy, you just open/import model.
Make sure gamma is set to 2.2 (prefference)
Create sun/sky system.
Enable/adjust exposure controls.
Create portal lights at all/any openings in the model (or where ever you want)
Turn on GI photons.
Optional...Turn on "All objects generate and recieve photons" or something worded similarly.

Thats the basic workflow in a nutshell. Sorry if you already knew these things, but I had to
learn Maya after years of working with Max. I actually really like both apps. But I know, for me, there was a huge difference between the integration plugins between them. Max was far simpler and more straight forward when it came to MR/Vray etc.

If you are used to mr for Maya, then you will probably really like mr for Max.


12 December 2010, 07:05 AM
I've used the method you've described but thanks anyway. I think I need to play with it again using GI as it didn't seem to work how i'd expect.

So do you know what the point is of the hidden shaders? I read these were important and allow you to optimise your portal light setup.

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12 December 2010, 07:05 AM
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