How does Blender Combine the Refraction Pass?

[blendercomp]

@FloridaJo

Okay, I’ll buy that.
Thanks for the clarification.

Sidenote: I’ve listened many hours to your tutorials so that when my wife asks me a question, I’m answering her in a German accent.
She: “How do you take the cap off this bottle?”
Me: (in German accent) "Well, first you must understand the bottle is glass and the lid is plastic, and the reason this was done was to prevent children from opening the bottle and removing the contents which would probably not be good for them if ingested in any quantities of more than a teaspoon or maybe a tablespoon, or even less if it is a pharmaceutical, so the thing to remember is what properties could best be connected between glass and plastic as it relates to friction…

I think she wants to hit me.

lol…this just made my day! :-))))

[sebastian_k]

@Nichod

I haven’t really had a need to use transparency in composites. It’s funny how rarely we truly use glass. But now I need to composite some glass in a scene. Is there some trick to it? Maybe it’s talked about in your cmivfx video?

Glass can be quite tricky, and it depends a lot on your scene and what you want to do. I do not talk about that specifically in the video.
Depending on what you want to do this might be a solution:
use camera-mapping / uv-projection to get your background image on a helper-plane or geometry and render your transparent glass object against that. Then use nodes and renderlayers to add that on top of your footage and maybe use a shadowcatcher plane to get some shadows and AO below your object.
Otherwise you can try to separate the layer with your object into passes and add/screen the refraction, specular and reflection on top of your footage.

[sebastian_k]

@blendercomp

lol…this just made my day! :-))))

… and me blush…

[Nichod1 (Nichod)]

@sebastian_k

Glass can be quite tricky, and it depends a lot on your scene and what you want to do. I do not talk about that specifically in the video.
Depending on what you want to do this might be a solution:
use camera-mapping / uv-projection to get your background image on a helper-plane or geometry and render your transparent glass object against that. Then use nodes and renderlayers to add that on top of your footage and maybe use a shadowcatcher plane to get some shadows and AO below your object.
Otherwise you can try to separate the layer with your object into passes and add/screen the refraction, specular and reflection on top of your footage.

Well my problem is getting the transparency to be visualized correctly when the passes are recombined. I don’t see a specific transparency pass. So I’m guessing it’s part of refraction?

Or am I missing something?

[sebastian_k]

oh, yeah, transparency is refraction and needs to be added in the end. that and the whole passes topic is covered by the tutorial, btw.

[sebastian_k]

oh btw, nichod, awesome python tutorials! really useful and exactly what coding noobs like me need!

[Nichod1 (Nichod)]

@sebastian_k

oh, yeah, transparency is refraction and needs to be added in the end. that and the whole passes topic is covered by the tutorial, btw.

Hmm. Adding isn’t giving me a accurate result, so I’m guessing I’m doing something wrong. I added refraction last in the light render layers. If I have multiple passes with separate lights on different render layers do I combine (add) refraction last in each individual pass? After color adjustments or before? And do I do a refraction pass for AO?

@sebastian_k

oh btw, nichod, awesome python tutorials! really useful and exactly what coding noobs like me need!

Thanks. I have blenderscripts.org and eventually soon will be doing a lot more and redoing those.

[FloridaJo]

@sebastian_k

Uh oh, I guess in the next tutorials I can be a little bit more straightforward…

No, no, not at all. Your detailed explanations is what’s great about your tuts.
Don’t change a thing. They’re just right.
That technique just don’t work on wives.
Really don’t change.

[krt]

Hi

I have a problem with reflection pass. I can’t combine passes to look the same as combined image.

Screen shot:
http://www.shrani.si/f/3X/Lx/1KU4HdJB/passes.jpg