I’m trying to render an object with its shadow and reflection on a matte object. In the vraymtlwrapper there is a reflection amount parameter but no matter what I do, this doesn’t seem to work. At least it doesn’t show up in the alpha. Is there really no way to do this? It seems like a real deal breaker for us using vray at this point.
This is what I want:
Hi, i was asking the same questions. Seems like it is only possible in vray for Maya. I found this workaround:
http://www.workshop.mintviz.com/tutorials/matte-shadow-and-reflection-using-v-ray-2-0/
The method that Daniel suggested is one possibility (as a bonus, you get a separate mask for the reflections so you can tune their intensity); another is to follow this tutorial, which handles such (and many other) cases more elegantly: Chaos: Industry-leading design and visualization software (the section on “compositing basics”). The method described in the manual can handle correctly global illumination, reflections, refractions, shadows etc. which is not possible with a single matte/shadow material.
Best regards,
Vlado
Vlado, if this is possible in Maya now, can we expect it to be available to 3ds Max in the future? I understand the compositing tutorial will work in any situation, but I’m not sure why you think it is more elegant to render so many passes, when rendering one pass is so much easier. Also, what is point of having reflections in the matte material, but not in the alpha?
Because it handles all relevant effects - shadows, reflections, refractions - perfectly correctly with minimum trickery and complications.
when rendering one pass is so much easier.It is also quite limited. Matte materials are not physically accurate and a renderer must go through hoops to implement them, and sooner or later things start to fall apart.
Also, what is point of having reflections in the matte material, but not in the alpha?I don’t know really; it was not requested when the matte material was first implemented and I saw no specific reason to do. You can’t mask just the reflections out of the background, so any composite that relies only on the alpha is mostly wrong anyways. I’m not saying that the alpha is not useful in certain situations, but this was not made clear when we first implemented it, so it sort of stayed this way. I was also under the impression that reflections were usually rendered separately for greater control (so that you could tweak their strength for example).
Best regards,
Vlado
Btw for the next update, the matte reflections will produce an alpha channel. This will also be included for the nightly builds either today or tomorrow.
Best regards,
Vlado
Awesome! You just made my day.
cant find that option in the latest build. is it allready uploaded ?
Best regards
Björn
This is the nightly build from today; if you don’t have access to the nightly builds, please email our support guys to vray@chaosgroup.com
Best regards,
Vlado
vray_adv_23501_max2013_x64_22373.rar
is the one i downloaded. Are there other Subchapter in the nightlys that i maybe cant see with my acces rights ?
That’s the one, yes. Note that you must have reflections on the base material for the matte plane for this to work. I’m attaching my scene here.
Best regards,
Vlado
matte_reflections.zip (25 KB)
Sry my fault, i just figured that i have to enable color+alpha in the base materials reflection settings.
Now it seems to work.
Best regards
Björn
PS: thx for the fast reply 
Ah, yes - that too. I’d better make sure that it works even without that option though.
Best regards,
Vlado
But why, its an easy way to enable or disable it when you dont use it.
For example when u use an extra tex approach to have greater control over the reflections in composeting
Well yes, but maybe people will forget to turn it on… it’s easier for me if it stays the way it is now of course Would there ever be a case where you don’t want the alpha of the reflections?
Best regards,
Vlado
Befor this was implemented i used the vray extratex with vraydirt to get the alpha reflection.
The nice thing on this approach was that you can tweak the intensity of the reflections through the alpha channels opacity in AE.
But for that approch u need an clean alpha without reflections to compose it with the extratex output.
I would leave it as it is so its more flexible and when u handel with refractions you also have to keep in mind to switch the alpha behaviour in in the refractions rollout.
Best regards
Björn
Björn,
Wouldn’t it just be easier to setup using the matte material for a separate reflection pass? I never used the technique you are describing, but it seems like more work.
Well even if its usefull or not, one of the great advantages of vray is the possebility to tweak almost everything right for your needs to fit even the strangest workflows 
Hi Vlado.. any chance you can supply a 2011 version of this setup.. im having trouble getting it to work from scratch.
thanks.
