Portal object

[mattjakob]

Hello,
Im trying to create a portal... basically it's a box with one side open and some objects inside. I want to be able to see the objects from the open side but the remainder of the box to be see through.

Any idea ?

[houska]

If I understand correctly, this would be easiest to do in post-production. Do you have any online reference pictures of what you want to achieve?

[mattjakob]

Yes... with an object buffer it's super easy in post - I was wondering if there's a way to do it straight in the renderer

[houska]

I'm afraid not. Given that Corona is a photo-realistic renderer, you'd have come up with a way of simulating what you want with some arrangement of mirrors or something like that.

[jrgby]

Is this what you mean?
(added a wiretex around the portal box to illustrate better)



This is in max, but it's all material properties so hopefully works just the same in C4D:

1. portal box one side deleted, give this a material with full refraction at IoR 1.0
2. objects inside box have a material with the following:
    - rayswitch map into opacity slot with color set to black for refraction, the rest white
    - rayswitch map into refraction slot with color set to white for global illumination, rest black

If you don't set rayswitch in refraction slot then you get shadows from your scene showing up in the portal box when it's 'empty', this is the bit that's tricky.

[burnin]

Well, that's only half of the Portal & simpler to set in Cinema. ;)

1. Make a Portal Box (same as described above)
Remove front face and apply Glass material with IOR 1.0 (Note: "Thin" option doesn't work, since it has no refraction)

2. For Materials used inside the Portal Box simply untick and disable "Visibility in refractions" & "Visibility by GI" (under Material > Advanced tab)



But here's the problem: "How do you lit environment in the box differently?"
So it really looks like a portal to another dimension, space & time.
Something like Interior Mapping :)