Some tricky refraction/reflection/matte questions...

[Pixelcon]

So I have a bit of a difficult wish to explain.

This all becomes easier to understand when doing a lot of photoshop editing to glass and objects rendered behind glass.

The conditions are as follows:

1) Rendering glass with the refraction affect channels set to Color only I get nice solid reflections of transparent and reflective materials (glass). In the rawrefraction and refraction passes I get self-reflections (annoying as I'd prefer a "window" to the what's behind the glass. The most irritating thing about this setup is that multimatteelements have solid colours so they can't be used to mask any objects behind a reflective and transparent material.

2) Rendering glass with the refraction affect channels set to All channels I get transparent reflections. Annoying and somewhat useless when you want to boost glass reflections without boosting everything seen behind it. rawrefraction and refraction passes remain the same as above. The bonus here is the multimattes now employ transparency.

I have tried using flat planes as a test, setting the refraction IOR to 1.0 and reflective to whatever. If I turn OFF reflect on backside, I get refraction passes with no reflections. great but the material is pretty lifeless. Alas the problem essential is the same as above

Question 1) Can I please have transparent multimatteelements while getting reflection passes that have no transparency?

Question 2) Is there any conceivable way to get a refraction pass that isn't full of internal reflections and isn't single plane geometry?


And before anyone suggests I do separate passes for glass, I have tried this a few times before, and in particular on the last three projects I've worked on. I didn't find this method satisfactory at all as I had curtain walls with such insane curvature that rendering mirror glass and plopping it over the top was a nightmare to get it looking correct.

Thanks for reading!

- James

[Pixelcon]

So I have a bit of a difficult wish to explain.

This all becomes easier to understand when doing a lot of photoshop editing to glass and objects rendered behind glass.

The conditions are as follows:

1) Rendering glass with the refraction affect channels set to Color only I get nice solid reflections of transparent and reflective materials (glass). In the rawrefraction and refraction passes I get self-reflections (annoying as I'd prefer a "window" to the what's behind the glass. The most irritating thing about this setup is that multimatteelements have solid colours so they can't be used to mask any objects behind a reflective and transparent material.

2) Rendering glass with the refraction affect channels set to All channels I get transparent reflections. Annoying and somewhat useless when you want to boost glass reflections without boosting everything seen behind it. rawrefraction and refraction passes remain the same as above. The bonus here is the multimattes now employ transparency.

I have tried using flat planes as a test, setting the refraction IOR to 1.0 and reflective to whatever. If I turn OFF reflect on backside, I get refraction passes with no reflections. great but the material is pretty lifeless. Alas the problem essential is the same as above

Question 1) Can I please have transparent multimatteelements while getting reflection passes that have no transparency?

Question 2) Is there any conceivable way to get a refraction pass that isn't full of internal reflections and isn't single plane geometry?


And before anyone suggests I do separate passes for glass, I have tried this a few times before, and in particular on the last three projects I've worked on. I didn't find this method satisfactory at all as I had curtain walls with such insane curvature that rendering mirror glass and plopping it over the top was a nightmare to get it looking correct.

Thanks for reading!

- James

PS: I realize compositing in 32-bit would solve my problems, but for someone who's 8-bit photoshop files routinely end up at over 3gb, 32-bit isn't a viable option.

[thanulee]

Heya, try posting an image so its clear what u wanna achieve. cheers

[Pixelcon]

ok :P

Here's the Beauty pass:


Here's the Multimatte I want:


Here's the Multimatte I DON'Twant:


Here's the reflection pass when refraction is set to color only (What I wan't)


Here's the reflection pass when refraction is set to all channels (what I don't want)

[Pixelcon]

And here's a refraction pass full of self/internal reflections:

[thanulee]

I am a bit dizzy to realise whats up hahah but hey, i think the key to ur composite is the semi transparent multimatte right?

How about instead of multimatte, use self illum material with pure 255 red (ur diffuse needs to be black i think in this case) and color mapping linear or reinhardt at 1.0 (so it doesnt screw the value of ur red.) Add to that material some transparency with vraycolor map. Maybe what im saying is absolute crap

It occured to me though cause many times when multimatte does jagged edges on me, i turn everything black, and use vraylights with pure rgb values on the objects i want. Sorry if i wasted ur time

[Pixelcon]

But that means I need to do multiple renders which defeats the purpose of this thread all together :P

By chance I've stumbled across other having more or less the same "problem" with no real "solution" so...hrm...oh well

[thanulee]

IF this works, would be much faster than rendering ur scene twice. Just a separate render that will take u 5 minutes tops.
And yes, i have the same problem in many of my comps with glasses.