affect channels in reflection

[themaxxer]

affect channels in reflection - I ask myself for what I should use it? how does it work with which renderlement?
It sounds interesting and I would like to understand it...

best regards
themaxxer

[vlado]

It was done so that you could get material IDs and Z-depth through reflections (for the moment it works only for perfect reflections, not glossy ones) and also to get you the reflection alpha (which works with glossy reflections too).

Best regards,
Vlado

[themaxxer]

this reeeeeeally great. I can use this in my daily work. so, the new task is to make it work with glossies.

best regards
themaxxer

[PIXELBOX_SRO]

Hi guys,
so how do i get the pass?
where should appear? i cant really see ayn reflection alpha pass..
Whats the catch to get one?
Thanks

[Björn Radler]

Can somebody give an example of how reflections in alpha work exactly? I tried to get reflections on a matte surface but they dont show up in the alpha channel.

Maybe i get something wrong...little confused about that though.

Maybe Vlado can bring a little light into the dark


Best regards

Björn

[vlado]

This particular feature is not related to matte objects in any way.

If you need the alpha of the reflections, you could use an ExtraTex render element with VRayDirt in reflection occlusion mode.

Best regards,
Vlado

[Björn Radler]

Ahh ok, will try this out.


But whats the use of reflection alpha then, so i can stop damaging my brain with this



Best regards

Björn

[vlado]

Ah, good point. It will get you the alpha of the reflections. But, it has nothing to do with matte objects and will not work if you turn your object into a matte.

Best regards,
Vlado

[3ddesign]

It was done so that you could get material IDs and Z-depth through reflections (for the moment it works only for perfect reflections, not glossy ones) and also to get you the reflection alpha (which works with glossy reflections too).

Best regards,
Vlado

I've been doing some tests trying to use this but can't get it to work. Probably because, 1) I don't know what I'm doing or 2) I misunderstand what it is supposed to be able to do in the first place. Probably both.

What I'd like to do is get PSD Manager selection layers of objects that appear in a mirror. I've tried all the techniques I've found on the forum w/o success. Every project I do has mirrors and glass like the test image below. I need to be able to produce selection layers of every object and material in the mirror and those seen behind the glass (behind the glass is easier since I can just turn the glass off for a PSDM pass). I've resorted to doing a render with every object a unique bright color so I can at least use Select by Color but this doesn't work too well.



I started a thread here http://www.chaosgroup.com/forums/vbu...t-All-Channels but didn't understand what I was being told to do. I spend so much time in Photoshop hand selecting objects in mirrors that I would really reeeeeeally appreciate anyone who could hand hold me through learning how to do this.

Thanks. Craig

[jonahhawk]

Add a multimatte element to generate mattes for the objects by Object ID. In your image above, select the green box, go to object properties, set the Object ID (g-buffer) to a number other than 0 (zero). Let's say you set it to 1. Then in the MultiMatte element, check the box for any of the three channel mattes, red, green, or blue. Let's say you set the first one, the red channel, to ID 1.

Now in your Glass material, set the reflections to affect All Channels. There is a little drop down in both the reflection and refraction area. They are set to Color Only by default.

Now when you render, the multimatte element will be red where the object is directly visible AND where it appears in the reflections.

If you take it a step further, you can set a different object ID for the Mirrors and a corresponding id/channel in the multimatte. Then you can separate the matte for the green box in the reflections...

When in doubt, make mattes for everything. There are great scripts out there that will add multimattes for all selected objects or materials.

[3ddesign]

Jonahhawk,

Thank you for the very well written reply. I was able to get all reflection in my mirrors. But I must be doing something wrong trying to get objects seen through the glass. I've tried using the affects all channels in the refraction area but it isn't working.