Render only selected objects in a scene possible, while fully utilizing scene lighting?

[Anonymous]

I have a scene with a lighting setup and I desire to render an object separate from the scene and overlay the object in after effects for more post control. I need the scene so the objects lighting is correct. Is it possible to somehow force only one object to render, use the lighting of the scene and otherwise just export transparency all around the object?

edit:

Just FYI I selected all other objects in the scene I didn't want visible and unchecked visible to camera but left that reflections/shadows/etc are visible, and that does keep a lot of the scene lighting. Problem is, the object I want to single out has transparency. So I can see objects being refracted and reflected through the glass, although besides in glass, everything else is correct. If I disable reflections which a lot of the lighting of reflective surfaces depends on, lighting gets removed. Kinda a rock and hard place.

[Anonymous]

Do not use the environment for refract/reflect (standard) but use an exit color or a JPG to reflect.
But if there is nothing to reflect refract you just get white or black and a few speculars?

[Anonymous]

Another way to single out an object for render is the "Subset Pixels (of selected objects)" option in the Include in Render part of the RFW UI.
As for the reflections/refractions, well, you either want to see them, or you don't. It's that black and white.
If you only want just reflections and no refractions or vice-versa, a raytype switcher may do it, it's one of the hidden shaders.
Can you describe in more detail what you want to achieve? Then people will be better placed to guide you.

[Anonymous]

What would be ideal is everything other than the glass to reflect the environment it's in (which are all highly diffused, low subdivs and nothing can be easily seen in reflections so it's generic). And for glass to just be transparent so when I import it in with an alpha channel, I can see the proper reflections in objects but the glass has nothing already in it, just slight transparency.

edit for other response:

On what's mentioned above.. It's a interior of a building scene and a robot arm (think car assembly line, kuka-type robot arm) is holding what looks like a apple cinema display. A monitor. It brings the monitor toward the camera and fills the screen with it. The robot and the cinema display border are metal, the display portion of the screen is glass with slight transparency. I'm trying to turn off all of the interior scene around this robot arm and the screen it's holding while maintaining the same lighting. I was hoping to render the robot arm and display separate from the scene. Does that help?

Currently I deleted everything but the objects I want and I'm trying to render a picture of the interior and place it self-illuminated behind the thing I'm rendering, hoping it bounces off all the metals. But it doesn't 'surround' the robot arm so you can only see it at certain angles of reflection and isn't quite correct. Otherwise I'm just tossing in some V-Ray lights and I'm trying to get lighting similar to the previous scene. I thought there'd be a property of the glass I could adjust to keep it transparent but on rendering, not refract other objects, so the alpha channel comes out properly in the render.

[Anonymous]

You could render your object as separate "Render Elements" That will give you full control over the elements in your compositor.

[Anonymous]

Can you elaborate on what you mean by that? I'm working on a screenshot showing the various differences.

Thanks a bunch for the help!!

[Anonymous]

Look in the Max Help, in the Rendering section there is a sub-section called Rendering Elements Separately. That should explain what I mean.

I don't want to confuse things further, but it this thread relevant to what you are doing?
area.autodesk.com/forum/Autodesk-3ds-Max/materials/raytracing-and-alpha-channels-question/

[Anonymous]

Here's an example of what I'm dealing with, rendered with very low light calcs for speed.

On the left slice the frame is in the building scene. In the middle slice I've disabled "Visible to Camera" on all other objects. Note you can see refractions still through the glass. I like the metal but I just want transparent glass with an alpha channel. On the right I tried creating a new scene with new lights and threw planes with self-illuminated screenshot images of the building all around it but not visible to the camera. It's just not close at all to the original scene as you can see. But the glass is correct on the right, not refracting anything, just gray.

Image: Example Image

Edit:

About that link.. It goes over how to make max export an alpha channel and that's cool to know the option to check in 2009, which I'm using, but my problem is the middle slice of my example image. I'd just like the glass to export the proper amount of alpha (which it can), but not refract the original environment.

The real problem is reflections and refractions are joined as one single checkbox on object properties. If I could just tell max to render reflections but not refractions, it'd work just fine. But for it to export an alpha channel I think I need to have refraction on the glass part in the middle, and without deleting the scene (like in the right), it will continue to refract what's behind it.

[Anonymous]

Does your camera move at all? I'm thinking you could render out the background without the robot arm or monitor and save it for your background plate. Then render out a chrome ball in the center of your scene where your objects are going to be and save that for the reflections. Then you can use the Environment/Background Switcher for your background map. That should have all your lighting info from the relfections setup and you will have your robot arm and monitor with their own alpha channel for compositing.

Check out Samab's post at the end of this thread for setting up the chrome ball and background.
Link

[Anonymous]

Have you looked into Render Elements yet? That will let you individually alter the elements that make the whole image by putting them on different layers, reflections, refractions, specular, shadows Etc... You can Show/Hide them, reduce them, mask them in AE. Eg, if Refractions or AD Transparency Output is on a different layer you could put a rectangular mask on it.
Another way would be to render it all as is, then hide all the background and render just the foreground object with transparent alpha in the glass, then in AE use the alpha from the second render on the first render for it's mask.
Regarding the other thread, I think what you want is the opposite of what I suggested there. He wanted transparent alpha and to keep the refractions, which as Soulburn and I both explained, was kind of a contradiction, you get one or the other, the material is either transparent (see-through in a straight line) or refractive (bending the light rays as they pass the surface).
So I'm guessing you want see-through, not refractive. If you still want that glossy tinted look, that can all be done in AE with masked blurs and colour correction.
I don't know AE, but I have Combustion and Fusion, I assume they all share similar basic features. What I mean is when you go into a compositor, there is a lot of scope for altering stuff post render with masks that you can draw/paint or get from images/renders, and lots of effects too, if you don't get exactly what you want from your Max render. Render elements and objects on different layers increases this flexibility.

[Anonymous]

Regarding the other thread, I think what you want is the opposite of what I suggested there. He wanted transparent alpha and to keep the refractions, which as Soulburn and I both explained, was kind of a contradiction, you get one or the other, the material is either transparent (see-through in a straight line) or refractive (bending the light rays as they pass the surface).

I suggested that link to show him how to setup his scene for reflections from images, not so much the end result which was alphas and refractions. He wanted to have his robot arm and monitor with their own alpha to composite later, that is why I suggested making a chrome ball in his scene and setting up a background map to keep his reflections and lighting as he wants it. He can still render elements, but he needs the alphas without the background...

[Anonymous]

Thanks very much for the replies!

MK-3D~ Yes, my camera moves. A lot of the movement I'm doing is actually a combination of robot arm, screen and camera all together. So the reflections on the chrome ball would shift and I assume that option wouldn't work?

Samab~ Thanks for the suggestion on render elements! I'm just picking up this scene again now to play with it and haven't tried it but knowing max can seperate out these things in layers is very compelling! I will look into that right away.

Just to answer, yes I was only interested in transparency. I know refractions are calculated in max and there's no way for that to be calculated and saved for another application to read and utilized. I'm very acclimated to post work, just not 3d 😄

Thanks for your suggestion on rendering the scene as it is and then subtracting all the other elements and rendering out the second pass just for the alpha channel. That makes a lot of sense! That will give me just what I need and I will use that technique!

I'm very used to rotoscoping and posting work, usually over several iterations to achieve a certain look. I'm a multi-layer mask machine in after effects because it's very easy to do. I don't know combustion or fusion but you should take a peek at after effects! It's exactly like photoshop with a timeline and has some basic 3d support now (CS4). It's layer based and is very friendly to compositing, keying, correcting and tonalizing. Heck I even use it to straight up edit with here and there. One of the best things I like about it is it accepts a generous array of formats for assets (images/video/audio) and works with them equally well. It resizes video better than any other application I've ever used. Take a peek at Adobe.com!

I will report back on how this works! I just need to get my glass actually producing an alpha channel. I checked the "Affect alpha" checkbox on the glass material but for some reason it's coming out opaque. Might just need to uncheck trace refractions or something. I'll figure it out haha, then I'll report back!

[Anonymous]

Yes, my camera moves. A lot of the movement I’m doing is actually a combination of robot arm, screen and camera all together. So the reflections on the chrome ball would shift and I assume that option wouldn’t work?

I don't recommend Chrome Ball for moving camera shots, because the image is taken from a single angle and stick to the camera. It's really a cheap technique for capturing real world environments. If you want to go down the route of creating an environment map from a CGI scene, then it's better to render a panoramic view of the scene and map it spherically.
Incidentally, going OT a bit, doing a real world/CGI comp with a moving camera, with some kind of match move data, a chrome ball photo isn't totally useless. It can be unwrapped with HDR Shop to a lat-long panoramic image that can be sphereically mapped as an environment.

I’m very used to rotoscoping and posting work...

Good to see you are no stranger to this, I don't have to rattle on about masks and stuff to you.