VRayZDepth with Transparent Glass: Is there a way?

[landrvr1]

Anyone know of a way to get accurate ZDepth data when looking through glass? For the life of me I cannot figure it out and not even sure it's possible. Just trying to do nice Depth of Field work in post using After Effects. Everything works great except those pesky transparent materials, heh.

 

Tnx

[Ricardo Eloy]

Have you tried rendering a ZDepth pass without the glass and using it instead of the "original" pass? Could work, I guess.

 

 

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[landrvr1]

lol, yeah Rick that's what I figured too. Unfortunately you lose any nice crisp reflections that are occuring in your glass.

 

 

Actually, check out the car images on this page. There's a Mental Ray plug that does exactly what I'm looking for. At least I think it does; the page is all in German, heh.

 

http://forum.german-mentalray-wiki.info/viewtopic.php?p=1278#1278

[landrvr1]

Okay, a bit more digging over at Chaos and I found that if you select 'All Channels' on the materials Affect Channels setting, you'll get some workable alpha information when looking through glass.

 

However, you don't get any reflection data.

 

The hunt continues.....

 

[Thablanch]

This issue was fixed in SP4 (or SP3a mabee)

[landrvr1]

Well, heard from vlado over at Chaos. While it's true that SP3 fixed the ZDepth transparent material issue (as long as you select All Channels in the material), reflection data on transparent materials isn't possible.

 

vlado argues, correctly, that you would never get accurate data so why bother? He's right, of course. At best you simply get a lighter gray for the reflections in your closeup glass. Meaning that distant objects behind that part of the glass are less blurry, lol. Still, it's a start and something you could quickly fiddle with in post.

 

My challenge to him and the VRay team is to come up with a solution. This phenomenon happens every day in real life.

[landrvr1]

I'm now BEGGING you guys to help me solve this, lol.

 

I've been trying to figure this out over at chaos, but so far nothing....

 

How in the world can you just render just the reflection on a single object in a full scene.

 

I've been trying to figure out the DoF issue with reflective glass, but without using the DoF in VRay cam. It's way too expensive.

 

I can easily comp frames together in AfterFX, but the last piece of the puzzle is just getting REFLECTIONS ONLY for ONE OBJECT.

 

A VRay reflection element will not work. It reflects everything in the scene, of course.

 

Can this even be done? An include/exclude feature in the elements would solve this 100%, but that doesn't seem to be an option yet.

 

 

Okay, here's what I want to do. Very simple, right? lol.

 

 

This methodology would save enormous amounts of time as compared to using the VRay camera with DoF; an expensive process when dealing with a 3000+ frame animation.

And setting everything to 'visible to camera = off' just never works right. I end up getting funky things happening on the glass. Good in theory, bad in practice.

Edited February 3, 2010 by landrvr1

[landrvr1]

Part II.

 

After getting some tips on using a multimatte element, I set to work again.

 

main image

 

reflection pass

 

multimatte element

 

Okay, I'm back to where I started. The problem lies in the REFLECTION PASS. I guess I'm just not following this at all. I still don't understand how I can get an image where I just have the reflections occurring on my glass. That reflection pass is worthless because it's got reflections from everything in the scene. The keying out of the glass is easy. I knew how to do that already.

 

Am I not comping this correctly in AfterFX? Is it the format I'm saving in? Which is rpf?

 

This is driving me nuts. WHAT AM I MISSING HERE???????

[landrvr1]

lol.

 

Well, continuing on with my goal to always circle back here when I've found a solution to a problem...I'm pleased to say that there is a method to achieve DoF without the expensive VRay camera option.

 

It's a rather ingenious bit of AfterFX comping that dlparisi came up with over at the Chaos forum. Works like a charm.

 

http://www.chaosgroup.com/forums/vbulletin/showthread.php?48420-Rendering-the-REFLECTION-ONLY-for-ONE-OBJECT-in-a-scene

 

The much simpler solution would be the ability to exclude/include any objects from the Reflection render element, then do a very easy comp in AE or the post product of your choice. I've seen a few threads in which vlado says this might be coming. Let's hope so. VRay cams are way too expensive for my film workflow and deadlines.