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cyborg_ty
10-26-2014, 02:40 PM
Can an object be seen by one camera but not by another?
I have been playing with the RayTrace node for projecting animated facial expressions on Lego characters. So I created 'facial_cams' that are dedicated to particular animated expression objects (and then mapped to the faces using Raytrace node on to the characters' head objects). There is also a main camera and I do not want this camera to render any of the facial expression objects. The obvious solution is to move the expression objects out of field of view, but this becomes tedious as I change the point of view of the main camera.

So, is there a way to hide the Lego expression object from the main camera but still have it seen by another camera? Or put another way, is there a way to have an object in the line of sight (or field of view) of two cameras, but have it hidden from one camera but seen by the other?

Slartibartfast
10-26-2014, 11:21 PM
Afc now but i'd check if there is a way to make some node logic in the dissolve channel.

meshpig
10-26-2014, 11:55 PM
Object Properties/Render "unseen by camera".

erikals
10-27-2014, 12:01 AM
Object Properties/Render "unseen by camera"
but it would still cast a shadow i guess...

maybe the shadow could be set to render invisible based on an incidence angle somehow...

meshpig
10-27-2014, 12:10 AM
... cast shadow = no :)

erikals
10-27-2014, 01:32 AM
ah, good stuff... http://erikalstad.com/backup/misc.php_files/smile.gif

pinkmouse
10-27-2014, 02:42 AM
...The obvious solution is to move the expression objects out of field of view, but this becomes tedious as I change the point of view of the main camera...So, is there a way to hide the Lego expression object from the main camera but still have it seen by another camera? Or put another way, is there a way to have an object in the line of sight (or field of view) of two cameras, but have it hidden from one camera but seen by the other?.

I feel you're over-complicating things. Why not just parent the expression objects and their camera to the main camera? Then if they start out of shot, they'll stay out of shot...:)

prometheus
10-27-2014, 10:00 AM
yeah unseen by camera, but that requires rendering two passes to render, since it is unseen per object basis and will make it unseen for all cameras.
and shadows can be turned of as well.

meshpig
10-28-2014, 01:57 AM
The obvious flaw. Needs something like camera depth in game engines, I'm thinking item info/raycast (length) in relation to the 2 cameras?

Sensei
10-28-2014, 05:32 AM
Or put another way, is there a way to have an object in the line of sight (or field of view) of two cameras, but have it hidden from one camera but seen by the other?

Are you using standard backdrop environment?
You could try putting quad in path between one camera and object you don't want to see from it.
Quad would be "transparent" one way - single faced.
Plug node from TrueArt's Node Library (http://www.trueart.eu) > Tools > Backdrop to Make Material.

I made video tutorial showing how to use this technique.
https://www.youtube.com/watch?v=COGlpVeGniw

cyborg_ty
10-28-2014, 07:53 AM
I appreciate ALL of your eagerness to provide an answer / solution to my issue. Thank you for your replies.

It appears setting the object to 'Unseen by Camera' in the object properties is what I needed. The RayTrace node still works as long as the 'Unseen by Rays' property is not selected.
125238

Sensei
10-28-2014, 08:03 AM
It appears setting the object to 'Unseen by Camera' in the object properties is what I needed. The RayTrace node still works as long as the 'Unseen by Rays' property is not selected.

If you will have reflective, refractive surface in the scene, it'll cause problem..
It will also affect GI and lighting.