Corona - Object and Material ID's

[MGDesignUK]

Hi People,

I can't figure out how best to make material ID's and object ID's like when using Vray. I have set up the 'CMasking_ID' and have gone through the options there but doesn't appear to be a setting that allows you to make a red, green or blue mask for materials or objects.

Any insight into how people are getting around masking objects; such as grass or trees then please let me know. I'm using version 6 for people's reference.

Many thanks in advance,
Max

[MGDesignUK]

No one got any ideas?

[MGDesignUK]

Here is an example of what I mean; how is one suppose to mask those trees out in the background?

[johan belmans]

It is not the bet option but I always select the inverse (selection)